| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:CommonStockValue | ██████▇▇▇▇▇▇▇▇▆▆▆▆▁▁▁▁▁▁▁▁▁ | 19362.0 | 19336.0 | 19303.0 | 19238.0 | 19209.0 | 19171.0 | 19063.0 | 19008.0 | 18973.0 | 18964.0 | 18862.0 | 18860.0 | 18807.0 | 18794.0 | 18756.0 | 18722.0 | 18676.0 | 18647.0 | 16755.0 | 16731.0 | 16709.0 | 16679.0 | 16651.0 | 16751.0 | 16741.0 | 16716.0 | 16693.0 |
| us-gaap:SharesIssued | ▁▁▁▁▁█▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁ | 977.405 | 976.337 | 976.24 | 973.941 | 973.417 | 972786.0 | 968.842 | 967.739 | 967.214 | 965.168 | 962.685 | 961.92 | 960.84 | 958.778 | 958.014 | 957.616 | 954.668 | 954.545 | 896.61 | 895.979 | 894.568 | 894.208 | NA | NA | 892.034 | NA | NA |
| us-gaap:CommonStockSharesOutstanding | ███▇▇▇▇▇▇▆▆▆▁▁ | 976.0 | 975.0 | 974.0 | 972.0 | 972.0 | 970.954879 | 967.009746 | 965.906701 | 965.381919 | 963.335888 | 960.852473 | 960.087898 | 926.09666 | 924.035059 | NA | NA | 919.924742 | NA | 861.24355 | 861.24355 | 859.833343 | NA | 893.9406 | 858.721507 | 857.290484 | 856.563385 | 856.563385 |
| us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding | ████████▇▇▇▆▅▅▅▅▅▄▁▁▁▁▁▁▁▁▁ | 977.0 | 976.0 | 976.0 | 974.0 | 974.0 | 972.0 | 970.0 | 969.0 | 968.0 | 967.0 | 965.0 | 936.0 | 930.0 | 928.0 | 927.0 | 926.0 | 924.0 | 915.0 | 866.0 | 867.0 | 868.0 | 863.0 | 864.0 | 861.0 | 860.0 | 860.0 | 860.0 |
| us-gaap:WeightedAverageNumberOfSharesOutstandingBasic | ███████▇▇▇▇▆▅▅▅▅▅▄▁▁▁▁▁▁▁▁▁ | 976.0 | 976.0 | 975.0 | 973.0 | 972.0 | 971.0 | 968.0 | 967.0 | 966.0 | 964.0 | 962.0 | 934.0 | 928.0 | 925.0 | 925.0 | 924.0 | 921.0 | 913.0 | 863.0 | 862.0 | 861.0 | 861.0 | 860.0 | 858.0 | 856.0 | 857.0 | 856.0 |
| us-gaap:AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | ██▁ | 1.0 | 1.0 | 0.0 | NA | 0.0 | 0.0 | 2.0 | 2.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | 4.0 | 13.0 | 15.0 | NA | 2.0 | 16.0 | 18.0 | NA | 20.0 | 17.0 |
| us-gaap:EarningsPerShareBasic | ▃▃▃▄▃▄▄▃▃█▄▁▅▂▃▂▂▃▄▄▁▅▃▁▃▄▃ | 0.51 | 0.53 | 0.6 | 0.79 | 0.5 | 0.93 | 0.76 | 0.56 | 0.61 | 1.94 | 0.86 | 0.09 | 1.07 | 0.22 | 0.53 | 0.29 | 0.34 | 0.69 | 0.74 | 0.8 | 0.02 | 1.15 | 0.61 | 0.1 | 0.6 | 0.86 | 0.57 |
| us-gaap:EarningsPerShareDiluted | ▃▃▃▄▃▄▄▃▃█▄▁▅▂▃▂▂▃▄▄▁▅▃▁▃▄▃ | 0.51 | 0.53 | 0.6 | 0.79 | 0.5 | 0.93 | 0.76 | 0.56 | 0.6 | 1.93 | 0.85 | 0.09 | 1.07 | 0.22 | 0.53 | 0.29 | 0.33 | 0.69 | 0.74 | 0.8 | 0.02 | 1.15 | 0.6 | 0.1 | 0.59 | 0.86 | 0.57 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cost Ratio dei:LegalEntity exc:AtlanticCityElectricCompany | █▁▂█▂▂▇▁▃▂▆▂▂▂█▂▂▇▂▄ | 420.0 | 256.0 | 276.0 | 419.0 | 274.0 | 273.0 | 406.0 | 265.0 | 310.0 | 271.0 | 370.0 | 270.0 | 275.0 | 275.0 | 421.0 | 270.0 | 291.0 | 386.0 | 285.0 | 334.0 | NA | NA | NA | NA | NA | NA | NA |
| Cost Ratio dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▃▁▆▂▂▇▃▂▇▄▃▂▆▄▄▂▃▃▁█▃▂▂█▄▃▂ | 731.0 | 616.0 | 937.0 | 703.0 | 649.0 | 976.0 | 731.0 | 662.0 | 977.0 | 813.0 | 738.0 | 674.0 | 951.0 | 812.0 | 812.0 | 680.0 | 746.0 | 725.0 | 628.0 | 1036.0 | 761.0 | 697.0 | 653.0 | 1054.0 | 794.0 | 737.0 | 653.0 |
| Cost Ratio dei:LegalEntity exc:CommonwealthEdisonCo | █▅▆▇▄▅▇▅▆▄▇▅▄▃▆▄▃▅▂▂▁▃▂▂▁▂▁ | 1643.0 | 1417.0 | 1439.0 | 1583.0 | 1351.0 | 1408.0 | 1598.0 | 1398.0 | 1512.0 | 1309.0 | 1571.0 | 1357.0 | 1298.0 | 1223.0 | 1497.0 | 1286.0 | 1196.0 | 1376.0 | 1148.0 | 1185.0 | 1079.0 | 1222.0 | 1128.0 | 1134.0 | 1068.0 | 1156.0 | 1080.0 |
| Cost Ratio dei:LegalEntity exc:DelmarvaPowerandLightCompany | ▄▁▅▃▂▆▄▂▆▄▄▂▅▃▄▂▂▃▁█ | 337.0 | 267.0 | 350.0 | 319.0 | 287.0 | 380.0 | 328.0 | 289.0 | 384.0 | 330.0 | 327.0 | 282.0 | 362.0 | 303.0 | 331.0 | 281.0 | 296.0 | 314.0 | 271.0 | 421.0 | NA | NA | NA | NA | NA | NA | NA |
| Cost Ratio dei:LegalEntity exc:ExelonGenerationCoLLC | ▄▂▅▅▃▆▆▄▇▄▅▃▅▃▅▁▃▅▃█▅▄▂▃▂▃▂ | 4659.0 | 3880.0 | 4733.0 | 4774.0 | 4210.0 | 5296.0 | 5278.0 | 4579.0 | 5512.0 | 4654.0 | 4751.0 | 4174.0 | 4888.0 | 4388.0 | 5035.0 | 3589.0 | 4294.0 | 4768.0 | 4232.0 | 5840.0 | 4802.0 | 4412.0 | 3789.0 | 4390.0 | 3772.0 | 4255.0 | 4070.0 |
| Cost Ratio dei:LegalEntity exc:PecoEnergyCo | ▅▂▅▄▁▆▃▁▆▃▃▁▄▂▄▂▁▃▂█▃▂▂█▄▃▂ | 813.0 | 681.0 | 813.0 | 778.0 | 655.0 | 900.0 | 757.0 | 653.0 | 866.0 | 729.0 | 715.0 | 630.0 | 796.0 | 701.0 | 788.0 | 664.0 | 645.0 | 740.0 | 661.0 | 985.0 | 750.0 | 693.0 | 656.0 | 993.0 | 805.0 | 728.0 | 672.0 |
| Cost Ratio dei:LegalEntity exc:PepcoHoldingsLLC | █▁▄█▂▅█▂▆▃▇▂▄ | 1368.0 | 1016.0 | 1171.0 | 1380.0 | 1091.0 | 1228.0 | 1361.0 | 1076.0 | 1251.0 | 1121.0 | 1310.0 | 1074.0 | 1175.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Cost Ratio dei:LegalEntity exc:PotomacElectricPowerCompany | ▇▁▄█▃▅▇▃▄▂▆▂▃▁█▂▁▆▂▄ | 611.0 | 494.0 | 544.0 | 642.0 | 531.0 | 575.0 | 628.0 | 523.0 | 557.0 | 510.0 | 604.0 | 514.0 | 530.0 | 491.0 | 635.0 | 509.0 | 488.0 | 592.0 | 504.0 | 545.0 | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:AtlanticCityElectricCompany | █▁▂█▂▂▇▁▃▂▆▂▂▂█▂ | 420.0 | 256.0 | 276.0 | 419.0 | 274.0 | 273.0 | 406.0 | 265.0 | 310.0 | 271.0 | 370.0 | 270.0 | 275.0 | 275.0 | 421.0 | 270.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▃▁▇▃▂█▃▂█▅▃▂▇▅▅▂ | 731.0 | 616.0 | 937.0 | 703.0 | 649.0 | 976.0 | 731.0 | 662.0 | 977.0 | 813.0 | 738.0 | 674.0 | 951.0 | 812.0 | 812.0 | 680.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:CommonwealthEdisonCo | █▄▅▇▃▄▇▄▆▂▇▃▂▁▆▂ | 1643.0 | 1417.0 | 1439.0 | 1583.0 | 1351.0 | 1408.0 | 1598.0 | 1398.0 | 1512.0 | 1309.0 | 1571.0 | 1357.0 | 1298.0 | 1223.0 | 1497.0 | 1286.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:DelmarvaPowerandLightCompany | ▅▁▆▄▂█▅▂█▅▅▂▇▃▅▂ | 337.0 | 267.0 | 350.0 | 319.0 | 287.0 | 380.0 | 328.0 | 289.0 | 384.0 | 330.0 | 327.0 | 282.0 | 362.0 | 303.0 | 331.0 | 281.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:ExelonGenerationCoLLC | ▅▂▅▅▃▇▇▅█▅▅▃▆▄▆▁ | 4659.0 | 3880.0 | 4733.0 | 4774.0 | 4210.0 | 5296.0 | 5278.0 | 4579.0 | 5512.0 | 4654.0 | 4751.0 | 4174.0 | 4888.0 | 4388.0 | 5035.0 | 3589.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:PecoEnergyCo | ▆▂▆▅▂█▄▂▇▄▃▁▅▃▅▂ | 813.0 | 681.0 | 813.0 | 778.0 | 655.0 | 900.0 | 757.0 | 653.0 | 866.0 | 729.0 | 715.0 | 630.0 | 796.0 | 701.0 | 788.0 | 664.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:PepcoHoldingsLLC | █▁▄█▂▅█▂▆▃▇▂▄ | 1368.0 | 1016.0 | 1171.0 | 1380.0 | 1091.0 | 1228.0 | 1361.0 | 1076.0 | 1251.0 | 1121.0 | 1310.0 | 1074.0 | 1175.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity exc:PotomacElectricPowerCompany | ▇▁▃█▃▅▇▂▄▂▆▂▃▁█▂ | 611.0 | 494.0 | 544.0 | 642.0 | 531.0 | 575.0 | 628.0 | 523.0 | 557.0 | 510.0 | 604.0 | 514.0 | 530.0 | 491.0 | 635.0 | 509.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin dei:LegalEntity,us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments exc:PepcoHoldingsLLC,us-gaap:CorporateNonSegment,us-gaap:CorporateAndOther | ▁▃▂▁▃▆▅▆█ | 91.0 | 97.0 | 93.0 | 92.0 | 97.0 | 106.0 | 103.0 | 108.0 | 113.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:AtlanticCityElectricCompany | █▁▂█▂▂▇▁▃ | 420.0 | 256.0 | 276.0 | 419.0 | 274.0 | 273.0 | 406.0 | 265.0 | 310.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:BaltimoreGasAndElectricCompany | ▃▁▇▃▂█▃▂█ | 731.0 | 616.0 | 937.0 | 703.0 | 649.0 | 976.0 | 731.0 | 662.0 | 977.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:CommonwealthEdisonCo | █▃▃▇▁▂▇▂▅ | 1643.0 | 1417.0 | 1439.0 | 1583.0 | 1351.0 | 1408.0 | 1598.0 | 1398.0 | 1512.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:DelmarvaPowerandLightCompany | ▅▁▆▄▂█▅▂█ | 337.0 | 267.0 | 350.0 | 319.0 | 287.0 | 380.0 | 328.0 | 289.0 | 384.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:ExelonGenerationCoLLC | ▄▁▅▅▂▇▇▄█ | 4659.0 | 3880.0 | 4733.0 | 4774.0 | 4210.0 | 5296.0 | 5278.0 | 4579.0 | 5512.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:PecoEnergyCo | ▆▂▆▅▁█▄▁▇ | 813.0 | 681.0 | 813.0 | 778.0 | 655.0 | 900.0 | 757.0 | 653.0 | 866.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:PepcoHoldingsLLC | █▁▄█▂▅█▂▆ | 1368.0 | 1016.0 | 1171.0 | 1380.0 | 1091.0 | 1228.0 | 1361.0 | 1076.0 | 1251.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| EBT Margin us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,exc:PotomacElectricPowerCompany | ▇▁▃█▃▅▇▂▄ | 611.0 | 494.0 | 544.0 | 642.0 | 531.0 | 575.0 | 628.0 | 523.0 | 557.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Operating Margin dei:LegalEntity exc:AtlanticCityElectricCompany | █▁▂█▂▂▇▁▃▂▆▂▂▂█▂▂▇▂▄ | 420.0 | 256.0 | 276.0 | 419.0 | 274.0 | 273.0 | 406.0 | 265.0 | 310.0 | 271.0 | 370.0 | 270.0 | 275.0 | 275.0 | 421.0 | 270.0 | 291.0 | 386.0 | 285.0 | 334.0 | NA | NA | NA | NA | NA | NA | NA |
| Operating Margin dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▃▁▆▂▂▇▃▂▇▄▃▂▆▄▄▂▃▃▁█▃▂▂█▄▃▂ | 731.0 | 616.0 | 937.0 | 703.0 | 649.0 | 976.0 | 731.0 | 662.0 | 977.0 | 813.0 | 738.0 | 674.0 | 951.0 | 812.0 | 812.0 | 680.0 | 746.0 | 725.0 | 628.0 | 1036.0 | 761.0 | 697.0 | 653.0 | 1054.0 | 794.0 | 737.0 | 653.0 |
| Operating Margin dei:LegalEntity exc:CommonwealthEdisonCo | █▅▆▇▄▅▇▅▆▄▇▅▄▃▆▄▃▅▂▂▁▃▂▂▁▂▁ | 1643.0 | 1417.0 | 1439.0 | 1583.0 | 1351.0 | 1408.0 | 1598.0 | 1398.0 | 1512.0 | 1309.0 | 1571.0 | 1357.0 | 1298.0 | 1223.0 | 1497.0 | 1286.0 | 1196.0 | 1376.0 | 1148.0 | 1185.0 | 1079.0 | 1222.0 | 1128.0 | 1134.0 | 1068.0 | 1156.0 | 1080.0 |
| Operating Margin dei:LegalEntity exc:DelmarvaPowerandLightCompany | ▄▁▅▃▂▆▄▂▆▄▄▂▅▃▄▂▂▃▁█ | 337.0 | 267.0 | 350.0 | 319.0 | 287.0 | 380.0 | 328.0 | 289.0 | 384.0 | 330.0 | 327.0 | 282.0 | 362.0 | 303.0 | 331.0 | 281.0 | 296.0 | 314.0 | 271.0 | 421.0 | NA | NA | NA | NA | NA | NA | NA |
| Operating Margin dei:LegalEntity exc:ExelonGenerationCoLLC | ▄▂▅▅▃▆▆▄▇▄▅▃▅▃▅▁▃▅▃█▅▄▂▃▂▃▂ | 4659.0 | 3880.0 | 4733.0 | 4774.0 | 4210.0 | 5296.0 | 5278.0 | 4579.0 | 5512.0 | 4654.0 | 4751.0 | 4174.0 | 4888.0 | 4388.0 | 5035.0 | 3589.0 | 4294.0 | 4768.0 | 4232.0 | 5840.0 | 4802.0 | 4412.0 | 3789.0 | 4390.0 | 3772.0 | 4255.0 | 4070.0 |
| Operating Margin dei:LegalEntity exc:PecoEnergyCo | ▅▂▅▄▁▆▃▁▆▃▃▁▄▂▄▂▁▃▂█▃▂▂█▄▃▂ | 813.0 | 681.0 | 813.0 | 778.0 | 655.0 | 900.0 | 757.0 | 653.0 | 866.0 | 729.0 | 715.0 | 630.0 | 796.0 | 701.0 | 788.0 | 664.0 | 645.0 | 740.0 | 661.0 | 985.0 | 750.0 | 693.0 | 656.0 | 993.0 | 805.0 | 728.0 | 672.0 |
| Operating Margin dei:LegalEntity exc:PepcoHoldingsLLC | █▁▄█▂▅█▂▆▃▇▂▄ | 1368.0 | 1016.0 | 1171.0 | 1380.0 | 1091.0 | 1228.0 | 1361.0 | 1076.0 | 1251.0 | 1121.0 | 1310.0 | 1074.0 | 1175.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Operating Margin dei:LegalEntity exc:PotomacElectricPowerCompany | ▇▁▄█▃▅▇▃▄▂▆▂▃▁█▂▁▆▂▄ | 611.0 | 494.0 | 544.0 | 642.0 | 531.0 | 575.0 | 628.0 | 523.0 | 557.0 | 510.0 | 604.0 | 514.0 | 530.0 | 491.0 | 635.0 | 509.0 | 488.0 | 592.0 | 504.0 | 545.0 | NA | NA | NA | NA | NA | NA | NA |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TTM Greenblatt ROC _ _ | ▄▃▇▇▅▇▆▅▆▇█▁▇▄▇▄▄▇▆▇▄█▅▁▅▇▅ | 769.0 | 565.0 | 1220.0 | 1353.0 | 841.0 | 1218.0 | 1146.0 | 942.0 | 1101.0 | 1258.0 | 1475.0 | 232.0 | 1296.0 | 714.0 | 1267.0 | 647.0 | 707.0 | 1200.0 | 1134.0 | 1366.0 | 705.0 | 1400.0 | 829.0 | 163.0 | 889.0 | 1254.0 | 1005.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:ComprehensiveIncomeNetOfTax | ▄▄▄▅▄▅▅▄▅█▅▃▅▃▄▄▃▄▅▅▁▆▅▃▆▅▄ | 529.0 | 562.0 | 603.0 | 799.0 | 506.0 | 890.0 | 785.0 | 582.0 | 656.0 | 1973.0 | 868.0 | 115.0 | 985.0 | 46.0 | 562.0 | 337.0 | 263.0 | 619.0 | 683.0 | 749.0 | -672.0 | 1063.0 | 688.0 | 97.0 | 1115.0 | 748.0 | 497.0 |
| us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest | ██▁▆▆██▆██▇▆▆█▇▇▆▅▆ | 68.0 | 53.0 | -206.0 | -9.0 | 9.0 | 58.0 | 67.0 | 4.0 | 52.0 | 67.0 | 43.0 | -16.0 | -16.0 | 49.0 | 31.0 | 39.0 | -19.0 | -42.0 | -5.0 | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | ▃▃▂▃▃▄▄▃▃█▄▁▄▁▃▂▂▃▃ | 597.0 | 615.0 | 397.0 | 790.0 | 515.0 | 948.0 | 852.0 | 586.0 | 708.0 | 2040.0 | 911.0 | 99.0 | 969.0 | 137.0 | 531.0 | 298.0 | 263.0 | 661.0 | 688.0 | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CostOfGoodsAndServicesSoldDepreciationAndAmortization | █▁▁▃▃▃▄▃ | 1289.0 | 1001.0 | 1021.0 | 1083.0 | 1079.0 | 1075.0 | 1105.0 | 1088.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CostsAndExpenses | ▇▄▆▆▄▇▇▅█▅▅▆▆▅▆▃▃▃▂▆▅▂▂▅▁▁▁ | 8087.0 | 6769.0 | 7529.0 | 7559.0 | 6881.0 | 8262.0 | 8252.0 | 7138.0 | 8648.0 | 7334.0 | 7300.0 | 7392.0 | 7691.0 | 7072.0 | 7736.0 | 6294.0 | 6001.0 | 6203.0 | 5387.0 | 7465.0 | 7016.0 | 5513.0 | 5456.0 | 7055.0 | 5277.0 | 5285.0 | 5115.0 |
| us-gaap:GainLossOnInvestments | ▇█▁▆▆▇▆▅▅▆▆▆▆▅▆▅▆▄▅▅▆▅▆▅▆▆▅ | 255.0 | 455.0 | -651.0 | 63.0 | 96.0 | 308.0 | 101.0 | -12.0 | -68.0 | 187.0 | 145.0 | 109.0 | 175.0 | -14.0 | 129.0 | 59.0 | 90.0 | -223.0 | -45.0 | 47.0 | 69.0 | -27.0 | 142.0 | 26.0 | 75.0 | 68.0 | -39.0 |
| us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | ▅▅▁▇▄█▆▄▅▇█▁▇▃▆▃ | 786.0 | 794.0 | 85.0 | 1102.0 | 644.0 | 1282.0 | 947.0 | 613.0 | 702.0 | 1225.0 | 1326.0 | 1.0 | 1206.0 | 392.0 | 871.0 | 415.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:IncomeTaxExpenseBenefit | ▇▇▄▆▆▇▆▆▆▁█▅▇▆▇▆▇▆▇▇▅█▇▅▇█▇ | 216.0 | 219.0 | -294.0 | 172.0 | 144.0 | 310.0 | 137.0 | 66.0 | 59.0 | -720.0 | 452.0 | -72.0 | 215.0 | 136.0 | 340.0 | 102.0 | 268.0 | 115.0 | 327.0 | 363.0 | 20.0 | 422.0 | 277.0 | -54.0 | 311.0 | 439.0 | 239.0 |
| us-gaap:InterestExpense | ▆▆▆▆▆▆▆▅▅▅▅▆▅▅█▅▃▃▁▅▅▃▃▂▃▃▃ | 398.0 | 421.0 | 404.0 | 403.0 | 403.0 | 397.0 | 387.0 | 367.0 | 365.0 | 359.0 | 377.0 | 426.0 | 363.0 | 347.0 | 506.0 | 366.0 | 268.0 | 243.0 | 145.0 | 335.0 | 333.0 | 247.0 | 228.0 | 217.0 | 224.0 | 228.0 | 246.0 |
| us-gaap:NetIncomeLoss dei:LegalEntity exc:ExelonGenerationCoLLC | ▂▃▂▂▂▃▂▂▂█▃▁▃▂▂▂ | 49.0 | 476.0 | 45.0 | 257.0 | 108.0 | 363.0 | 234.0 | 178.0 | 136.0 | 2224.0 | 305.0 | -250.0 | 423.0 | -42.0 | 236.0 | -8.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetIncomeLossAttributableToNoncontrollingInterest | ██▁▆▇██▆█ | 68.0 | 53.0 | -206.0 | -12.0 | 10.0 | 59.0 | 67.0 | 3.0 | 51.0 | NA | 42.0 | -1.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic | ▃▃▃▄▃▄▄▃▃█▄▁▅▂▃▂▂▃▃▄▁▅▃▁▃▄▃ | 501.0 | 521.0 | 582.0 | 772.0 | 484.0 | 907.0 | 733.0 | 539.0 | 585.0 | 1871.0 | 824.0 | 80.0 | 995.0 | 204.0 | 490.0 | 267.0 | 309.0 | 629.0 | 638.0 | 693.0 | 19.0 | 993.0 | 522.0 | 90.0 | 495.0 | 738.0 | 490.0 |
| us-gaap:NonoperatingIncomeExpense | ▇█▁▆▆▇▆▅▅▇▆▆▆▅▅▆▆▄▆▅▄▇▇▆▆▆▅ | 17.0 | 229.0 | -1135.0 | -251.0 | -197.0 | 64.0 | -199.0 | -329.0 | -399.0 | -35.0 | -149.0 | -231.0 | -90.0 | -321.0 | -396.0 | -232.0 | -145.0 | -497.0 | -172.0 | -265.0 | -590.0 | 96.0 | 5.0 | -124.0 | -84.0 | -79.0 | -269.0 |
| us-gaap:OperatingExpenses | ▆▁▄▄▁▇▇▂█ | 8087.0 | 6769.0 | 7529.0 | 7559.0 | 6881.0 | 8262.0 | 8252.0 | 7138.0 | 8648.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:OperatingIncomeLoss | ▄▃▇▇▅▇▆▅▆▇█▁▇▄▇▄▄▇▆▇▄█▅▁▅▇▅ | 769.0 | 565.0 | 1220.0 | 1353.0 | 841.0 | 1218.0 | 1146.0 | 942.0 | 1101.0 | 1258.0 | 1475.0 | 232.0 | 1296.0 | 714.0 | 1267.0 | 647.0 | 707.0 | 1200.0 | 1134.0 | 1366.0 | 705.0 | 1400.0 | 829.0 | 163.0 | 889.0 | 1254.0 | 1005.0 |
| us-gaap:OtherComprehensiveIncomeLossNetOfTax | ▅▅▅▅▅▅▅▅▅▅▅▅▅▄▅▅▅▅▅▅▁▅▆▅█▅▅ | 28.0 | 41.0 | 21.0 | 30.0 | 21.0 | -18.0 | 52.0 | 44.0 | 72.0 | 102.0 | 44.0 | 35.0 | -12.0 | -132.0 | 36.0 | 31.0 | -28.0 | 32.0 | 50.0 | 11.0 | -767.0 | -11.0 | 131.0 | 4.0 | 621.0 | 12.0 | 0.0 |
| us-gaap:OtherNonoperatingIncomeExpense | ▇█▁▅▆▇▆▅▅▆▆▆▆▅▅▅▅▃▅▅▃▆▆▅▅▅▅ | 421.0 | 656.0 | -725.0 | 158.0 | 212.0 | 467.0 | 194.0 | 44.0 | -28.0 | 331.0 | 237.0 | 205.0 | 283.0 | 36.0 | 120.0 | 144.0 | 133.0 | -244.0 | -17.0 | 80.0 | -247.0 | 354.0 | 243.0 | 103.0 | 162.0 | 155.0 | -17.0 |
| us-gaap:ProfitLoss | ▃▃▂▄▃▄▄▃▃█▄▁▅▂▃▂▂▃▃▄▁▅▃▁▃▄▃ | 569.0 | 574.0 | 376.0 | 760.0 | 494.0 | 966.0 | 800.0 | 542.0 | 636.0 | 1938.0 | 867.0 | 64.0 | 981.0 | 248.0 | 526.0 | 306.0 | 309.0 | 587.0 | 633.0 | 738.0 | 18.0 | 1074.0 | 557.0 | 93.0 | 495.0 | 736.0 | 497.0 |
| us-gaap:RegulatedOperatingRevenue | ▁▁▁▁▁██▇█▇█▇▇▇█▇▅▅▅▆ | -11.0 | -122.0 | 67.0 | -80.0 | -13.0 | 4503.0 | 4457.0 | 3797.0 | 4570.0 | 3946.0 | 4313.0 | 3715.0 | 4197.0 | 3793.0 | 4467.0 | 3676.0 | 2584.0 | 2837.0 | 2434.0 | 3198.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:AtlanticCityElectricCompany | █▁▇▇▆▇▇▇ | 5.0 | -26.0 | 1.0 | 1.0 | -2.0 | 1.0 | -1.0 | -1.0 | NA | 0.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▄▁█▄▅▆▄▄ | -9.0 | -37.0 | 36.0 | -5.0 | 6.0 | 10.0 | -6.0 | -4.0 | NA | 0.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:CommonwealthEdisonCo | ▃▄█▁▅▄▅▅ | -38.0 | -25.0 | 12.0 | -56.0 | -14.0 | -28.0 | -15.0 | -17.0 | NA | 0.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:DelmarvaPowerandLightCompany | █▁▇▅▆▆▆▇ | 8.0 | -25.0 | 1.0 | -6.0 | 0.0 | 0.0 | 0.0 | 4.0 | NA | 0.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:PecoEnergyCo | ██▇▁▄▄▆▇ | 5.0 | 4.0 | 2.0 | -11.0 | -3.0 | -3.0 | 1.0 | 2.0 | NA | 0.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:PepcoHoldingsLLC | █▁▇▅▅▇▅▅ | 31.0 | -64.0 | 18.0 | -9.0 | -3.0 | 15.0 | -5.0 | -7.0 | NA | 33.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:RegulatedOperatingRevenue dei:LegalEntity exc:PotomacElectricPowerCompany | █▁▇▃▄▇▃▂ | 18.0 | -13.0 | 15.0 | -3.0 | -1.0 | 14.0 | -4.0 | -10.0 | NA | 0.0 | 0.0 | 0.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:Revenues | ▆▃▆▇▄█▇▅█▅▆▄▆▅▇▃▂▄▂▆▃▃▁▃▁▂▁ | 8853.0 | 7322.0 | 8747.0 | 8929.0 | 7689.0 | 9477.0 | 9403.0 | 8076.0 | 9693.0 | 8381.0 | 8769.0 | 7623.0 | 8757.0 | 7875.0 | 9002.0 | 6910.0 | 6702.0 | 7401.0 | 6514.0 | 8830.0 | 7255.0 | 6912.0 | 6024.0 | 7237.0 | 6163.0 | 6502.0 | 6141.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 |
|---|
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:Assets | ███▇▇▇▇▇▆▆▇▆▆▆▆▆▃▃▃▂▂▂▂▁▁▁▁ | 127767.0 | 126313.0 | 124677.0 | 122738.0 | 121596.0 | 121593.0 | 119485.0 | 117249.0 | 117018.0 | 116700.0 | 118473.0 | 117104.0 | 117068.0 | 114904.0 | 114535.0 | 112778.0 | 95384.0 | 95128.0 | 92213.0 | 87391.0 | 86814.0 | 85264.0 | 83656.0 | 79468.0 | 79924.0 | 79661.0 | 78420.0 |
| us-gaap:Liabilities | ██▇▇▇▇▇▆▆▆▇▇▇▇▇▇▃▃▃▂▂▂▂▁▁▁▁ | 92664.0 | 91442.0 | 90061.0 | 88386.0 | 87689.0 | 87889.0 | 86097.0 | 84410.0 | 84453.0 | 84568.0 | 88156.0 | 87814.0 | 88777.0 | 87292.0 | 87049.0 | 85456.0 | 68062.0 | 67839.0 | 67144.0 | 62753.0 | 62681.0 | 60214.0 | 59427.0 | 56690.0 | 56984.0 | 57594.0 | 56832.0 |
| us-gaap:LiabilitiesAndStockholdersEquity | ███▇▇▇▇▆▆▆▇▆▆▆▆▆▃▃▃▂▂▂▂▁▁ | 127767.0 | 126313.0 | 124677.0 | 122738.0 | 121596.0 | 121593.0 | 119485.0 | 117249.0 | 117018.0 | 116700.0 | 118473.0 | 117104.0 | 117068.0 | 114904.0 | 114535.0 | 112778.0 | 95384.0 | 95128.0 | 92213.0 | 87391.0 | 86814.0 | 85264.0 | 83656.0 | 79468.0 | 79924.0 | NA | NA |
| us-gaap:StockholdersEquity | ███▇▇▇▇▇▆▆▅▅▄▄▄▄▄▄▂▂▂▂▂▂▂▁▁ | 32884.0 | 32703.0 | 32482.0 | 32023.0 | 31548.0 | 31357.0 | 31020.0 | 30515.0 | 30231.0 | 29857.0 | 28100.0 | 27546.0 | 26530.0 | 25837.0 | 26027.0 | 25756.0 | 25793.0 | 25770.0 | 23506.0 | 23065.0 | 22608.0 | 23595.0 | 22853.0 | 22568.0 | 22732.0 | 21859.0 | 21353.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:AssetsCurrent | ▄▄▄▄▃▄▅▃▃▃▄▄▄▄▄▃▇█▇▃▄▃▁▁▂▂▁ | 12312.0 | 12533.0 | 12476.0 | 12206.0 | 11655.0 | 12476.0 | 13473.0 | 11489.0 | 11533.0 | 11834.0 | 12724.0 | 12232.0 | 12194.0 | 12412.0 | 12208.0 | 11495.0 | 15334.0 | 16867.0 | 15425.0 | 11357.0 | 12097.0 | 11837.0 | 9823.0 | 9675.0 | 10137.0 | 9951.0 | 9409.0 |
| us-gaap:Cash dei:LegalEntity,us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriods,us-gaap:BalanceSheetLocation exc:ExelonGenerationCoLLC,us-gaap:MaturityUpTo30Days,exc:NuclearDecommissioningTrustFundInvestments | █▅▁▂ | 121.0 | 101.0 | 78.0 | 85.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:Cash dei:LegalEntity,us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriods,us-gaap:FairValueByAssetClass,us-gaap:FairValueByMeasurementFrequency exc:ExelonGenerationCoLLC,us-gaap:MaturityUpTo30Days,exc:NuclearDecommissioningTrustFundInvestments,us-gaap:FairValueMeasurementsRecurring | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:Cash us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriods,us-gaap:BalanceSheetLocation us-gaap:MaturityUpTo30Days,exc:NuclearDecommissioningTrustFundInvestments | █▅▁▂ | 121.0 | 101.0 | 78.0 | 85.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:Cash us-gaap:AssetsSoldUnderAgreementsToRepurchaseMaturityPeriods,us-gaap:FairValueByAssetClass,us-gaap:FairValueByMeasurementFrequency us-gaap:MaturityUpTo30Days,exc:NuclearDecommissioningTrustFundInvestments,us-gaap:FairValueMeasurementsRecurring | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:CashAndCashEquivalentsAtCarryingValue | ▂▃▂▂▁▁▂▁▁▁▂▁▁▁▂▂▇█▇▂▂▃▂▁▂▂▁ | 1858.0 | 2129.0 | 1457.0 | 1683.0 | 735.0 | 880.0 | 1918.0 | 694.0 | 787.0 | 898.0 | 1203.0 | 536.0 | 609.0 | 635.0 | 1897.0 | 1647.0 | 6502.0 | 7265.0 | 6014.0 | 1825.0 | 1878.0 | 2763.0 | 1362.0 | 914.0 | 1609.0 | 1644.0 | 991.0 |
| us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents | ▇█▅▆▂▃▇▂▂▂▄▁▁▁▁ | 2480.0 | 2680.0 | 1992.0 | 2178.0 | 1178.0 | 1314.0 | 2321.0 | 1028.0 | 1099.0 | 1190.0 | 1545.0 | 811.0 | 889.0 | 914.0 | 889.0 | NA | 914.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:AccountsReceivableNetCurrent | ▂▂▆▇▆█▇▆▇▇▅▅▆▇▆▅▃▃▃▅▄▂▂▂▁▁▁ | 2792.0 | 2814.0 | 4042.0 | 4188.0 | 4125.0 | 4564.0 | 4239.0 | 4094.0 | 4190.0 | 4401.0 | 3854.0 | 3825.0 | 3886.0 | 4158.0 | 4061.0 | 3671.0 | 3187.0 | 3215.0 | 3227.0 | 3702.0 | 3482.0 | 2815.0 | 2973.0 | 2997.0 | 2721.0 | 2584.0 | 2609.0 |
| us-gaap:InventoryNet dei:LegalEntity exc:AtlanticCityElectricCompany | ▆▅▅█▆▅▄▁▃▃ | 34.0 | 32.0 | 32.0 | 37.0 | 34.0 | 32.0 | 31.0 | 25.0 | 29.0 | 29.0 | NA | NA | NA | 22.0 | NA | NA | 23.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:InventoryNet dei:LegalEntity exc:CommonwealthEdisonCo | ▇█▇█▆▆▆▆▆▆▆▇▇▇▇▇█▆▆▅▄▃▂▂▂▁▁ | 160.0 | 166.0 | 161.0 | 162.0 | 151.0 | 152.0 | 146.0 | 146.0 | 146.0 | 152.0 | 152.0 | 160.0 | 154.0 | 159.0 | 156.0 | 155.0 | 164.0 | 148.0 | 144.0 | 135.0 | 125.0 | 121.0 | 112.0 | 107.0 | 109.0 | 103.0 | 102.0 |
| us-gaap:InventoryNet dei:LegalEntity exc:PotomacElectricPowerCompany | ▆▆▆█▇▆▁▂▃▂ | 110.0 | 109.0 | 109.0 | 118.0 | 115.0 | 109.0 | 81.0 | 85.0 | 89.0 | 87.0 | NA | NA | NA | 63.0 | NA | NA | 67.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:OtherAssetsCurrent | █▇▅▄▃▄▃▄▅▄▄▅▃▂▃▃▁▃▁▂▂▃▂▂▁▁▁ | 2277.0 | 2139.0 | 1629.0 | 1296.0 | 1218.0 | 1406.0 | 1177.0 | 1360.0 | 1495.0 | 1242.0 | 1435.0 | 1600.0 | 1221.0 | 930.0 | 1064.0 | 1101.0 | 748.0 | 1178.0 | 654.0 | 793.0 | 865.0 | 1022.0 | 775.0 | 901.0 | 666.0 | 699.0 | 690.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:AssetsNoncurrent dei:LegalEntity,us-gaap:ConsolidatedEntities exc:AtlanticCityElectricCompany,us-gaap:VariableInterestEntityPrimaryBeneficiary | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent dei:LegalEntity,us-gaap:ConsolidatedEntities exc:ExelonGenerationCoLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent dei:LegalEntity,us-gaap:ConsolidatedEntities exc:PepcoHoldingsLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent dei:LegalEntity,us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities exc:AtlanticCityElectricCompany,us-gaap:VariableInterestEntityPrimaryBeneficiary | ▁█ | 10.0 | 11.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:AssetsNoncurrent dei:LegalEntity,us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities exc:ExelonGenerationCoLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | █▁ | 8941.0 | 8869.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:AssetsNoncurrent dei:LegalEntity,us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities exc:PepcoHoldingsLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | ▁█ | 11.0 | 14.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:AssetsNoncurrent us-gaap:ConsolidatedEntities us-gaap:VariableInterestEntityPrimaryBeneficiary | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities us-gaap:VariableInterestEntityPrimaryBeneficiary | █▁ | 8952.0 | 8883.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:PropertyPlantAndEquipmentGross | NA | NA | NA | NA | NA | NA | NA | NA | NA | 95266.0 | NA | NA | NA | 90724.0 | NA | NA | 73814.0 | NA | NA | NA | 66829.0 | NA | NA | NA | 61043.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:AtlanticCityElectricCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 3772.0 | NA | NA | NA | 3537.0 | NA | NA | 3291.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:BaltimoreGasAndElectricCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 11007.0 | NA | NA | NA | 10294.0 | NA | NA | 9613.0 | NA | NA | NA | 9072.0 | NA | NA | NA | 8566.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:CommonwealthEdisonCo | NA | NA | NA | NA | NA | NA | NA | NA | NA | 24992.0 | NA | NA | NA | 23272.0 | NA | NA | 21212.0 | NA | NA | NA | 19225.0 | NA | NA | NA | 17850.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 4826.0 | NA | NA | NA | 4448.0 | NA | NA | 4209.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | 36334.0 | NA | NA | NA | 36147.0 | NA | NA | 34482.0 | NA | NA | NA | 30557.0 | NA | NA | NA | 27145.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:PecoEnergyCo | NA | NA | NA | NA | NA | NA | NA | NA | NA | 11464.0 | NA | NA | NA | 10818.0 | NA | NA | 10242.0 | NA | NA | NA | 9718.0 | NA | NA | NA | 9319.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:PepcoHoldingsLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | 12985.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity exc:PotomacElectricPowerCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 9178.0 | NA | NA | NA | 8621.0 | NA | NA | 8091.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:AtlanticCityElectricCompany,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:AtlanticCityElectricCompany,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 3607.0 | NA | NA | NA | 3341.0 | NA | NA | 3105.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:AtlanticCityElectricCompany,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 27.0 | NA | NA | NA | 27.0 | NA | NA | 28.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:BaltimoreGasAndElectricCompany,exc:CommonElectricAndGasTAndDEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 771.0 | NA | NA | NA | 707.0 | NA | NA | 655.0 | NA | NA | NA | 623.0 | NA | NA | NA | 578.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:BaltimoreGasAndElectricCompany,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:BaltimoreGasAndElectricCompany,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 7464.0 | NA | NA | NA | 7067.0 | NA | NA | 6663.0 | NA | NA | NA | 6339.0 | NA | NA | NA | 6100.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:BaltimoreGasAndElectricCompany,us-gaap:GasDistributionEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 2379.0 | NA | NA | NA | 2170.0 | NA | NA | 1951.0 | NA | NA | NA | 1761.0 | NA | NA | NA | 1660.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:BaltimoreGasAndElectricCompany,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 26.0 | NA | NA | NA | 32.0 | NA | NA | 32.0 | NA | NA | NA | 32.0 | NA | NA | NA | 32.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:CommonwealthEdisonCo,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:CommonwealthEdisonCo,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 24423.0 | NA | NA | NA | 22636.0 | NA | NA | 20576.0 | NA | NA | NA | 18884.0 | NA | NA | NA | 17334.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:CommonwealthEdisonCo,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 52.0 | NA | NA | NA | 67.0 | NA | NA | 64.0 | NA | NA | NA | 65.0 | NA | NA | NA | 60.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:DelmarvaPowerandLightCompany,exc:CommonElectricAndGasTAndDEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 117.0 | NA | NA | NA | 115.0 | NA | NA | 108.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:DelmarvaPowerandLightCompany,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:DelmarvaPowerandLightCompany,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 3875.0 | NA | NA | NA | 3574.0 | NA | NA | 3431.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:DelmarvaPowerandLightCompany,us-gaap:GasDistributionEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 614.0 | NA | NA | NA | 580.0 | NA | NA | 547.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:DelmarvaPowerandLightCompany,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 15.0 | NA | NA | NA | 16.0 | NA | NA | 16.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:ExelonGenerationCoLLC,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:ExelonGenerationCoLLC,us-gaap:ElectricGenerationEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 29019.0 | NA | NA | NA | 27193.0 | NA | NA | 25615.0 | NA | NA | NA | 22911.0 | NA | NA | NA | 20420.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:ExelonGenerationCoLLC,us-gaap:NuclearFuel | NA | NA | NA | NA | NA | NA | NA | NA | NA | 6420.0 | NA | NA | NA | 6546.0 | NA | NA | 6384.0 | NA | NA | NA | 5947.0 | NA | NA | NA | 5196.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:ExelonGenerationCoLLC,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 57.0 | NA | NA | NA | 76.0 | NA | NA | 466.0 | NA | NA | NA | 295.0 | NA | NA | NA | 400.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PecoEnergyCo,exc:CommonElectricAndGasTAndDEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 710.0 | NA | NA | NA | 670.0 | NA | NA | 631.0 | NA | NA | NA | 618.0 | NA | NA | NA | 600.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PecoEnergyCo,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PecoEnergyCo,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 7975.0 | NA | NA | NA | 7591.0 | NA | NA | 7230.0 | NA | NA | NA | 6886.0 | NA | NA | NA | 6669.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PecoEnergyCo,us-gaap:GasDistributionEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 2504.0 | NA | NA | NA | 2348.0 | NA | NA | 2206.0 | NA | NA | NA | 2039.0 | NA | NA | NA | 1932.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PecoEnergyCo,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 21.0 | NA | NA | NA | 21.0 | NA | NA | 21.0 | NA | NA | NA | 21.0 | NA | NA | NA | 17.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PepcoHoldingsLLC,exc:CommonElectricAndGasTAndDEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 82.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PepcoHoldingsLLC,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PepcoHoldingsLLC,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 11517.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PepcoHoldingsLLC,us-gaap:GasDistributionEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 449.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PepcoHoldingsLLC,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 102.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PotomacElectricPowerCompany,us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PotomacElectricPowerCompany,us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 8646.0 | NA | NA | NA | 8018.0 | NA | NA | 7682.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross dei:LegalEntity,us-gaap:PropertyPlantAndEquipmentByType exc:PotomacElectricPowerCompany,us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 59.0 | NA | NA | NA | 66.0 | NA | NA | 91.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType exc:CommonElectricAndGasTAndDEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 1447.0 | NA | NA | NA | 1312.0 | NA | NA | 1149.0 | NA | NA | NA | 1169.0 | NA | NA | NA | 1101.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:ConstructionInProgress | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:ElectricGenerationEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 29019.0 | NA | NA | NA | 27193.0 | NA | NA | 25615.0 | NA | NA | NA | 22911.0 | NA | NA | NA | 20420.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:ElectricTransmissionAndDistribution | NA | NA | NA | NA | NA | NA | NA | NA | NA | 49506.0 | NA | NA | NA | 45698.0 | NA | NA | 32546.0 | NA | NA | NA | 30157.0 | NA | NA | NA | 28123.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:GasDistributionEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 5050.0 | NA | NA | NA | 4642.0 | NA | NA | 3864.0 | NA | NA | NA | 3505.0 | NA | NA | NA | 3296.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:NuclearFuel | NA | NA | NA | NA | NA | NA | NA | NA | NA | 6420.0 | NA | NA | NA | 6546.0 | NA | NA | 6384.0 | NA | NA | NA | 5947.0 | NA | NA | NA | 5196.0 | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross us-gaap:PropertyPlantAndEquipmentByType us-gaap:OtherCapitalizedPropertyPlantAndEquipment | NA | NA | NA | NA | NA | NA | NA | NA | NA | 999.0 | NA | NA | NA | 1027.0 | NA | NA | 1181.0 | NA | NA | NA | 973.0 | NA | NA | NA | 1017.0 | NA | NA | |
| us-gaap:ConstructionInProgressGross dei:LegalEntity,us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:ExelonGenerationCoLLC,exc:Braidwood,us-gaap:FacilityClosing | ▁▁█ | 18.0 | 18.0 | 32.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ConstructionInProgressGross dei:LegalEntity,us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:ExelonGenerationCoLLC,exc:BraidwoodLaSalle,us-gaap:FacilityClosing | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:ConstructionInProgressGross dei:LegalEntity,us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:ExelonGenerationCoLLC,exc:BraidwoodLasalle,us-gaap:FacilityClosing | ▄ | 41.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ConstructionInProgressGross dei:LegalEntity,us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:ExelonGenerationCoLLC,exc:LaSalle,us-gaap:FacilityClosing | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:ConstructionInProgressGross dei:LegalEntity,us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:ExelonGenerationCoLLC,exc:Lasalle,us-gaap:FacilityClosing | ▄ | 23.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ConstructionInProgressGross us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:Braidwood,us-gaap:FacilityClosing | ▁▁█ | 18.0 | 18.0 | 32.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ConstructionInProgressGross us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:BraidwoodLasalle,us-gaap:FacilityClosing | ▄ | 41.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ConstructionInProgressGross us-gaap:PublicUtility,us-gaap:RestructuringCostAndReserve exc:Lasalle,us-gaap:FacilityClosing | █▁ | 23.0 | 19.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment | ██▇▇▇▇▇▆▆▆▅▅▅▄▄▃▃▃▂▂▂▂▂▂▁▁▁ | 25582.0 | 24798.0 | 24449.0 | 23590.0 | 24266.0 | 23695.0 | 23122.0 | 22302.0 | 21905.0 | 21064.0 | 20591.0 | 19735.0 | 19716.0 | 19169.0 | 18354.0 | 17340.0 | 16375.0 | 16185.0 | 15553.0 | 15207.0 | 14742.0 | 14932.0 | 14369.0 | 14066.0 | 13713.0 | 13366.0 | 12905.0 |
| us-gaap:AmortizationOfIntangibleAssets | ▂▂▂▂▂▂▂▂▂█▂▂▂█▁▂▆▂▁▁ | 16.0 | 15.0 | 16.0 | 15.0 | 14.0 | 15.0 | 15.0 | 15.0 | 13.0 | 49.0 | 15.0 | 14.0 | 14.0 | 49.0 | 10.0 | 14.0 | 37.0 | 15.0 | 12.0 | 12.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:PropertyPlantAndEquipmentNet | ███▇▇▇▇▇▆▆▆▆▆▆▆▆▃▃▃▂▂▂▂▁▁▁▁ | 82561.0 | 81748.0 | 81017.0 | 78593.0 | 78030.0 | 77460.0 | 75840.0 | 75284.0 | 74711.0 | 74202.0 | 73067.0 | 72748.0 | 72630.0 | 71555.0 | 71214.0 | 70693.0 | 57439.0 | 55814.0 | 53935.0 | 53001.0 | 52087.0 | 51630.0 | 51747.0 | 47742.0 | 47330.0 | 46495.0 | 45994.0 |
| us-gaap:LongTermInvestments | ▁▁▁▁▃▃▃▃▃▃▃▃▃▃▃▂▃▃▃▂▂▂▅▅███ | 444.0 | 424.0 | 418.0 | 471.0 | 618.0 | 620.0 | 649.0 | 636.0 | 640.0 | 640.0 | 634.0 | 638.0 | 648.0 | 629.0 | 592.0 | 502.0 | 639.0 | 620.0 | 607.0 | 568.0 | 544.0 | 562.0 | 839.0 | 825.0 | 1165.0 | 1154.0 | 1171.0 |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities srt:ParentCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:ExelonBusinessServicesCoAffiliate | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:ExelonEnergyDeliveryCompanyLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:ExelonEnterprise | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:ExelonGenerationCoLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:ExelonINQB8RLLCMember | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:OtherAffiliate | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:PotomacCapitalInvestmentAffiliate | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures us-gaap:ConsolidatedEntities,us-gaap:RelatedPartyTransactionsByRelatedParty srt:ParentCompany,exc:UIILLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:Goodwill | ████████████████▁▁▁▁▁▁▁▁▁▁▁ | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6677.0 | 6672.0 | 6696.0 | 2672.0 | 2672.0 | 2672.0 | 2672.0 | 2672.0 | 2672.0 | 2674.0 | 2625.0 | 2625.0 | 2625.0 | 2625.0 |
| us-gaap:FiniteLivedIntangibleAssetsNet | NA | NA | NA | NA | NA | NA | NA | NA | NA | -27.0 | NA | NA | NA | -279.0 | NA | NA | 755.0 | NA | NA | NA | 738.0 | NA | NA | NA | 417.0 | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet dei:LegalEntity,us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:BusinessServicesCompany,us-gaap:LicensingAgreements | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet dei:LegalEntity,us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:ExelonGenerationCoLLC,exc:UnamortizedEnergyContracts | NA | NA | NA | NA | NA | NA | NA | NA | NA | 364.0 | NA | NA | NA | 383.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet dei:LegalEntity,us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:ExelonGenerationCoLLC,us-gaap:CustomerRelationships | NA | NA | NA | NA | NA | NA | NA | NA | NA | 172.0 | NA | NA | NA | 190.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet dei:LegalEntity,us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:ExelonGenerationCoLLC,us-gaap:TradeNames | NA | NA | NA | NA | NA | NA | NA | NA | NA | 95.0 | NA | NA | NA | 118.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet dei:LegalEntity,us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:PepcoHoldingsLLC,exc:UnamortizedEnergyContracts | NA | NA | NA | NA | NA | NA | NA | NA | NA | -749.0 | NA | NA | NA | -1085.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:AtlanticCityElectricCompany,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:BaltimoreGasAndElectricCompany,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:CommonwealthEdisonCo,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:DelmarvaPowerandLightCompany,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:ExelonGenerationCoLLC,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:PecoEnergyCo,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:PepcoHoldingsLLC,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:BalanceSheetLocation exc:PotomacElectricPowerCompany,us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset dei:LegalEntity,us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:ExelonGenerationCoLLC,exc:LongtermContractforPurchaseofElectricPower | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset us-gaap:BalanceSheetLocation us-gaap:OtherNoncurrentAssets | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset us-gaap:FiniteLivedIntangibleAssetsByMajorClass exc:LongtermContractforPurchaseofElectricPower | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OtherAssetsNoncurrent | ██████▃▂▂▂▂▂▃▃▃▂▃▃▂▂▂▂▁▁▁▂▂ | 3165.0 | 3101.0 | 3164.0 | 3123.0 | 3038.0 | 3017.0 | 1560.0 | 1194.0 | 1333.0 | 1322.0 | 1277.0 | 1265.0 | 1440.0 | 1472.0 | 1474.0 | 1366.0 | 1445.0 | 1499.0 | 1388.0 | 1234.0 | 1160.0 | 1139.0 | 1092.0 | 934.0 | 964.0 | 1121.0 | 1175.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:AccountsPayableCurrent | ▆▅▅▇▆▇▇▆▆█▆▆▅█▅▄▅▅▄▄▅▃▃▂▂▂▁ | 3182.0 | 3047.0 | 2883.0 | 3348.0 | 3248.0 | 3327.0 | 3348.0 | 3113.0 | 3207.0 | 3532.0 | 3132.0 | 3134.0 | 3011.0 | 3441.0 | 3044.0 | 2826.0 | 2883.0 | 2987.0 | 2727.0 | 2839.0 | 3048.0 | 2502.0 | 2633.0 | 2475.0 | 2314.0 | 2369.0 | 2210.0 |
| us-gaap:AccruedLiabilitiesCurrent | ▃▂▂▃▂▃▃▂▂▃▇▆▇█▇▆▅▂▁▁▂▂▁▁▂▂▁ | 1879.0 | 1616.0 | 1535.0 | 1877.0 | 1706.0 | 1725.0 | 1964.0 | 1665.0 | 1569.0 | 1835.0 | 3080.0 | 2878.0 | 3007.0 | 3460.0 | 3236.0 | 2757.0 | 2376.0 | 1576.0 | 1366.0 | 1230.0 | 1539.0 | 1462.0 | 1382.0 | 1364.0 | 1633.0 | 1540.0 | 1382.0 |
| us-gaap:ContractWithCustomerLiabilityCurrent | █▁▁▁▁▁▂▁ | 149.0 | 20.0 | 29.0 | 26.0 | 21.0 | 25.0 | 37.0 | 28.0 | NA | 35.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LiabilitiesCurrent | ▅▅▆▇▇▆▄▄▄▅▆██▇▆▆▃▂▁▂▃▃▃▂▂▂▃ | 11262.0 | 11065.0 | 11774.0 | 13085.0 | 12934.0 | 12229.0 | 10140.0 | 9626.0 | 10153.0 | 10796.0 | 12395.0 | 13965.0 | 14437.0 | 13457.0 | 12158.0 | 11894.0 | 9118.0 | 7847.0 | 6526.0 | 7374.0 | 8762.0 | 8431.0 | 8567.0 | 7351.0 | 7728.0 | 7507.0 | 8374.0 |
| us-gaap:LongTermDebtCurrent | NA | NA | NA | NA | NA | NA | NA | NA | NA | 2088.0 | NA | NA | NA | 2430.0 | NA | NA | 1500.0 | NA | NA | NA | 1802.0 | NA | NA | NA | 1509.0 | NA | NA | |
| us-gaap:LongTermDebtCurrent dei:LegalEntity exc:BaltimoreGasAndElectricCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebtCurrent dei:LegalEntity exc:CommonwealthEdisonCo | NA | NA | NA | NA | NA | NA | NA | NA | NA | 840.0 | NA | NA | NA | 425.0 | NA | NA | 665.0 | NA | NA | NA | 260.0 | NA | NA | NA | 617.0 | NA | NA | |
| us-gaap:LongTermDebtCurrent dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 79.0 | NA | NA | NA | 105.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebtCurrent dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | 346.0 | NA | NA | NA | 1117.0 | NA | NA | 90.0 | NA | NA | NA | 614.0 | NA | NA | NA | 561.0 | NA | NA | |
| us-gaap:LongTermDebtCurrent dei:LegalEntity exc:PecoEnergyCo | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:OtherLiabilitiesCurrent | ██▆▇▇▆▂▃▂▃▂▃▂▃▄▃▁▃▂▃▄▃▃▂▁▁▁ | 1475.0 | 1474.0 | 1276.0 | 1425.0 | 1367.0 | 1245.0 | 935.0 | 973.0 | 956.0 | 982.0 | 933.0 | 977.0 | 942.0 | 981.0 | 1068.0 | 1025.0 | 842.0 | 1017.0 | 941.0 | 1018.0 | 1123.0 | 985.0 | 994.0 | 932.0 | 858.0 | 838.0 | 823.0 |
| us-gaap:TaxesPayableCurrent | ▂▁▇▆█ | 403.0 | 396.0 | 442.0 | 431.0 | 446.0 | NA | NA | NA | NA | 373.0 | NA | NA | NA | 723.0 | NA | NA | 293.0 | 150.0 | 360.0 | 65.0 | 305.0 | NA | NA | 285.0 | 315.0 | NA | NA |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:LiabilitiesNoncurrent dei:LegalEntity,us-gaap:ConsolidatedEntities exc:ExelonGenerationCoLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LiabilitiesNoncurrent dei:LegalEntity,us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities exc:AtlanticCityElectricCompany,us-gaap:VariableInterestEntityPrimaryBeneficiary | ▁█ | 6.0 | 11.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LiabilitiesNoncurrent dei:LegalEntity,us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities exc:ExelonGenerationCoLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | █▁ | 3223.0 | 3197.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LiabilitiesNoncurrent dei:LegalEntity,us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities exc:PepcoHoldingsLLC,us-gaap:VariableInterestEntityPrimaryBeneficiary | ▁█ | 7.0 | 13.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LiabilitiesNoncurrent us-gaap:ConsolidatedEntities us-gaap:VariableInterestEntityPrimaryBeneficiary | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LiabilitiesNoncurrent us-gaap:InvestmentsByConsolidatedAndNonconsolidatedEntities us-gaap:VariableInterestEntityPrimaryBeneficiary | █▁ | 3230.0 | 3210.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LongTermDebt | NA | NA | NA | NA | NA | NA | NA | NA | NA | 34047.0 | NA | NA | NA | 33959.0 | NA | NA | 25761.0 | NA | NA | NA | 21404.0 | 131.0 | 131.0 | NA | 19408.0 | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:AtlanticCityElectricCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 1127.0 | NA | NA | NA | 1162.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:BaltimoreGasAndElectricCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 2600.0 | NA | NA | NA | 2599.0 | NA | NA | 2128.0 | NA | NA | NA | 2203.0 | NA | NA | NA | 2273.0 | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:CommonwealthEdisonCo | NA | NA | NA | NA | NA | NA | NA | NA | NA | 7882.0 | NA | NA | NA | 7307.0 | NA | NA | 6773.0 | NA | NA | NA | 6183.0 | NA | NA | NA | 5900.0 | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 1309.0 | NA | NA | NA | 1348.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | 8955.0 | NA | NA | NA | 9208.0 | NA | NA | 8919.0 | NA | NA | NA | 8134.0 | NA | 1.0 | NA | 7552.0 | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:PecoEnergyCo | NA | NA | NA | NA | NA | NA | NA | NA | NA | 3109.0 | NA | NA | NA | 2784.0 | NA | NA | 2784.0 | NA | NA | NA | 2434.0 | NA | NA | NA | 2384.0 | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:PepcoHoldingsLLC | NA | NA | NA | NA | NA | NA | NA | NA | NA | 5189.0 | NA | NA | NA | 5157.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity exc:PotomacElectricPowerCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | 2570.0 | NA | NA | NA | 2381.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt dei:LegalEntity,us-gaap:DebtInstrument,us-gaap:LongtermDebtType exc:ExelonGenerationCoLLC,exc:ExGenRenewablesIVDec2020,exc:NonRecourseDebt | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt us-gaap:ConsolidatedEntities srt:ParentCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt us-gaap:DebtInstrument,us-gaap:LongtermDebtType exc:ExGenRenewablesIVDec2020,exc:NonRecourseDebt | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebtNoncurrent | ███▇▇▇▇▇▇▇▆▆▆▆▇▆▄▄▄▃▂▂▂▂▁▂▁ | 35512.0 | 36112.0 | 34808.0 | 32056.0 | 31909.0 | 32960.0 | 34519.0 | 33179.0 | 32905.0 | 32176.0 | 31701.0 | 30315.0 | 31044.0 | 31575.0 | 32330.0 | 31541.0 | 23645.0 | 24541.0 | 25220.0 | 20519.0 | 19362.0 | 19200.0 | 18133.0 | 18247.0 | 17325.0 | 17583.0 | 16121.0 |
| us-gaap:DeferredTaxLiabilitiesNoncurrent us-gaap:ConsolidatedEntities srt:ParentCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType us-gaap:PensionPlansDefinedBenefit | NA | NA | NA | NA | NA | NA | NA | NA | NA | 3736.0 | NA | NA | NA | 4248.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:MinorityInterest | █▇▇████████▆▆▆▅▅▅▅▅▅▅▅▄▁▁▁▁ | 2219.0 | 2168.0 | 2134.0 | 2329.0 | 2359.0 | 2347.0 | 2368.0 | 2324.0 | 2334.0 | 2275.0 | 2217.0 | 1744.0 | 1761.0 | 1775.0 | 1433.0 | 1349.0 | 1308.0 | 1326.0 | 1370.0 | 1380.0 | 1332.0 | 1262.0 | 1183.0 | 17.0 | 15.0 | 15.0 | 42.0 |
| us-gaap:OtherLiabilitiesNoncurrent | █▇▇▇▇▇▄▃▃▃▃▂▂▂▃▂▁▄▅▄▄▃▃▃▅▅▅ | 3313.0 | 2964.0 | 3017.0 | 3123.0 | 3053.0 | 3158.0 | 2160.0 | 2087.0 | 2067.0 | 2097.0 | 1899.0 | 1828.0 | 1853.0 | 1827.0 | 1928.0 | 1876.0 | 1491.0 | 2231.0 | 2528.0 | 2166.0 | 2147.0 | 2104.0 | 2133.0 | 2093.0 | 2540.0 | 2514.0 | 2635.0 |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo | NA | NA | NA | 246.0 | 246.0 | 244.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:AtlanticCityElectricCompany | NA | NA | NA | 5.0 | 5.0 | 5.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:BaltimoreGasAndElectricCompany | NA | NA | NA | 31.0 | 31.0 | 32.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:CommonwealthEdisonCo | NA | NA | NA | 3.0 | 3.0 | 2.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | 12.0 | 12.0 | 11.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | 162.0 | 161.0 | 162.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:PepcoHoldingsLLC | NA | NA | NA | 43.0 | 42.0 | 42.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity exc:PotomacElectricPowerCompany | NA | NA | NA | 9.0 | 9.0 | 9.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree | NA | NA | NA | 179.0 | 177.0 | 174.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity exc:AtlanticCityElectricCompany | NA | NA | NA | 4.0 | 4.0 | 4.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity exc:CommonwealthEdisonCo | NA | NA | NA | 2.0 | 2.0 | 1.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | 12.0 | 11.0 | 11.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | 113.0 | 112.0 | 112.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity exc:PepcoHoldingsLLC | NA | NA | NA | 42.0 | 41.0 | 40.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity exc:PotomacElectricPowerCompany | NA | NA | NA | 9.0 | 8.0 | 8.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour | NA | NA | NA | 148.0 | 141.0 | 139.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour dei:LegalEntity exc:AtlanticCityElectricCompany | NA | NA | NA | 4.0 | 3.0 | 3.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour dei:LegalEntity exc:CommonwealthEdisonCo | NA | NA | NA | 1.0 | 1.0 | 0.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | 11.0 | 10.0 | 10.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | 100.0 | 99.0 | 99.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour dei:LegalEntity exc:PepcoHoldingsLLC | NA | NA | NA | 41.0 | 39.0 | 39.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour dei:LegalEntity exc:PotomacElectricPowerCompany | NA | NA | NA | 8.0 | 8.0 | 8.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive | NA | NA | NA | 1123.0 | 1051.0 | 1052.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity exc:BaltimoreGasAndElectricCompany | NA | NA | NA | 19.0 | 19.0 | 18.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity exc:DelmarvaPowerandLightCompany | NA | NA | NA | 53.0 | 52.0 | 52.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity exc:ExelonGenerationCoLLC | NA | NA | NA | 837.0 | 834.0 | 840.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity exc:PepcoHoldingsLLC | NA | NA | NA | 197.0 | 196.0 | 194.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity exc:PotomacElectricPowerCompany | NA | NA | NA | 43.0 | 43.0 | 42.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:StockholdersEquity | ███▇▇▇▇▇▆▆▅▅▄▄▄▄▄▄▂▂▂▂▂▂▂▁▁ | 32884.0 | 32703.0 | 32482.0 | 32023.0 | 31548.0 | 31357.0 | 31020.0 | 30515.0 | 30231.0 | 29857.0 | 28100.0 | 27546.0 | 26530.0 | 25837.0 | 26027.0 | 25756.0 | 25793.0 | 25770.0 | 23506.0 | 23065.0 | 22608.0 | 23595.0 | 22853.0 | 22568.0 | 22732.0 | 21859.0 | 21353.0 |
| us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | ████▇▇▇▇▇▆▆▅▄▄▄▄▄▄▃▃▂▃▂▂▂▁▁ | 35103.0 | 34871.0 | 34616.0 | 34352.0 | 33907.0 | 33704.0 | 33388.0 | 32839.0 | 32565.0 | 32132.0 | 30317.0 | 29290.0 | 28291.0 | 27612.0 | 27460.0 | 27298.0 | 27294.0 | 27289.0 | 25069.0 | 24638.0 | 24133.0 | 25050.0 | 24229.0 | 22778.0 | 22940.0 | 22067.0 | 21588.0 |
| us-gaap:CommonStockValue | ██████▇▇▇▇▇▇▇▇▆▆▆▆▁▁▁▁▁▁▁▁▁ | 19362.0 | 19336.0 | 19303.0 | 19238.0 | 19209.0 | 19171.0 | 19063.0 | 19008.0 | 18973.0 | 18964.0 | 18862.0 | 18860.0 | 18807.0 | 18794.0 | 18756.0 | 18722.0 | 18676.0 | 18647.0 | 16755.0 | 16731.0 | 16709.0 | 16679.0 | 16651.0 | 16751.0 | 16741.0 | 16716.0 | 16693.0 |
| us-gaap:AdditionalPaidInCapital dei:LegalEntity exc:CommonwealthEdisonCo | █▇▇▇▇▆▆▆▅▅▅▄▄▃▃▂▂▂▂▂▂▁▁▁▁▁▁ | 8060.0 | 7821.0 | 7697.0 | 7509.0 | 7446.0 | 7385.0 | 7209.0 | 7047.0 | 6935.0 | 6822.0 | 6738.0 | 6357.0 | 6250.0 | 6150.0 | 6022.0 | 5795.0 | 5677.0 | 5548.0 | 5516.0 | 5484.0 | 5468.0 | 5362.0 | 5304.0 | 5230.0 | 5190.0 | 5189.0 | 5188.0 |
| us-gaap:RetainedEarningsAccumulatedDeficit | ███▇▇▇▆▆▆▅▃▃▄▃▃▃▃▃▃▃▂▂▂▂▂▁▁ | 16749.0 | 16622.0 | 16475.0 | 15871.0 | 15452.0 | 15321.0 | 14949.0 | 14551.0 | 14346.0 | 13503.0 | 11950.0 | 11442.0 | 12720.0 | 12030.0 | 12121.0 | 11926.0 | 12068.0 | 12046.0 | 11704.0 | 11334.0 | 10910.0 | 11160.0 | 10435.0 | 10180.0 | 10358.0 | 10131.0 | 9660.0 |
| us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax | ▁▁▁▂▂▂▃▂▂▅▄▄▄▄▅▄▄▄▄▄▄██▇▇▄▄ | -3104.0 | -3132.0 | -3173.0 | -2963.0 | -2990.0 | -3012.0 | -2869.0 | -2921.0 | -2965.0 | -2487.0 | -2589.0 | -2633.0 | -2670.0 | -2660.0 | -2523.0 | -2565.0 | -2624.0 | -2596.0 | -2626.0 | -2673.0 | -2684.0 | -1917.0 | -1906.0 | -2036.0 | -2040.0 | -2661.0 | -2673.0 |
| us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax dei:LegalEntity exc:ExelonGenerationCoLLC | ▂▂▁▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▂▃▃▆▇▇█ | -36.0 | -39.0 | -41.0 | -36.0 | -36.0 | -36.0 | -31.0 | -33.0 | -34.0 | -37.0 | -36.0 | -40.0 | -41.0 | -54.0 | -56.0 | -65.0 | -63.0 | -60.0 | -47.0 | -53.0 | -36.0 | 11.0 | 37.0 | 193.0 | 214.0 | 243.0 | 275.0 |
| us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:ConsolidatedEntities srt:ParentCompany | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:TreasuryStockValue | ▁▁▁▁▁▁▁▁▁▁▁▁███████████████ | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 123.0 | 2300.0 | 2327.0 | 2327.0 | 2327.0 | 2300.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 | 2327.0 |
| us-gaap:MinorityInterest | █▇▇████████▆▆▆▅▅▅▅▅▅▅▅▄▁▁▁▁ | 2219.0 | 2168.0 | 2134.0 | 2329.0 | 2359.0 | 2347.0 | 2368.0 | 2324.0 | 2334.0 | 2275.0 | 2217.0 | 1744.0 | 1761.0 | 1775.0 | 1433.0 | 1349.0 | 1308.0 | 1326.0 | 1370.0 | 1380.0 | 1332.0 | 1262.0 | 1183.0 | 17.0 | 15.0 | 15.0 | 42.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:NetCashProvidedByUsedInOperatingActivities | ▄▄▃▇▅▃▇▆▄▅▇▅▃▃▇█▅▅▇▄▃▅▄▁▅▆▄ | 1542.0 | 1600.0 | 1080.0 | 2501.0 | 1854.0 | 1044.0 | 2806.0 | 2367.0 | 1502.0 | 1803.0 | 2779.0 | 1697.0 | 1201.0 | 1082.0 | 2810.0 | 3080.0 | 1942.0 | 1705.0 | 2479.0 | 1490.0 | 814.0 | 1892.0 | 1586.0 | 165.0 | 1949.0 | 2056.0 | 1479.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities | █▇▂▃▄▃▃▂▃▂▃▄▁▁▁▁▂▂▃▃▅▅▅▆▄▄▆ | -393.0 | -644.0 | -2075.0 | -1756.0 | -1673.0 | -1786.0 | -1763.0 | -1989.0 | -1857.0 | -2124.0 | -1830.0 | -1569.0 | -2411.0 | -2284.0 | -2342.0 | -2329.0 | -2133.0 | -2143.0 | -1795.0 | -1751.0 | -1223.0 | -1189.0 | -1176.0 | -1011.0 | -1424.0 | -1421.0 | -1078.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:AtlanticCityElectricCompany | ▃▆▄▆▄▁▆▃▇▇▇▅▅▅▇▇▅▆▅█ | -103.0 | -78.0 | -95.0 | -73.0 | -99.0 | -128.0 | -76.0 | -108.0 | -64.0 | -69.0 | -68.0 | -88.0 | -85.0 | -82.0 | -67.0 | -60.0 | -90.0 | -76.0 | -87.0 | -53.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▁▂▁▁▂▃▃▄▄▂▄▄▅▁▃▅▅▄▇▇▇▆▇▅▆▆█ | -286.0 | -263.0 | -289.0 | -300.0 | -281.0 | -257.0 | -231.0 | -205.0 | -223.0 | -263.0 | -203.0 | -202.0 | -181.0 | -296.0 | -239.0 | -184.0 | -184.0 | -216.0 | -143.0 | -132.0 | -142.0 | -148.0 | -145.0 | -187.0 | -162.0 | -152.0 | -103.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:CommonwealthEdisonCo | ▇▇▇█▇▇▇▇▇▇▇▇▇▆▇▁▆▇▇▇▇██████ | -550.0 | -532.0 | -501.0 | -444.0 | -452.0 | -492.0 | -509.0 | -486.0 | -523.0 | -565.0 | -565.0 | -637.0 | -529.0 | -766.0 | -606.0 | -1939.0 | -716.0 | -602.0 | -521.0 | -523.0 | -507.0 | -417.0 | -401.0 | -330.0 | -345.0 | -349.0 | -357.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:DelmarvaPowerandLightCompany | █▁▄▅▅▅▅▄▆▁▄▃▅▅▆▄▄▄▅▇ | -39.0 | -143.0 | -99.0 | -85.0 | -81.0 | -78.0 | -88.0 | -100.0 | -65.0 | -136.0 | -102.0 | -111.0 | -80.0 | -82.0 | -74.0 | -99.0 | -105.0 | -92.0 | -87.0 | -61.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:ExelonGenerationCoLLC | ██▂▄▃▃▄▂▃▃▃▄▁▃▁▂▁▁▂▂▄▃▃▃▂▂▃ | 1163.0 | 997.0 | -871.0 | -291.0 | -541.0 | -433.0 | -257.0 | -934.0 | -615.0 | -689.0 | -546.0 | -145.0 | -1212.0 | -573.0 | -1068.0 | -1006.0 | -1049.0 | -1170.0 | -951.0 | -899.0 | -336.0 | -417.0 | -420.0 | -594.0 | -767.0 | -771.0 | -513.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:PecoEnergyCo | ▂▄▂▃▃▃▃▃▃▄▃▃▆▁▄▇▄▄▄▄▃▄▄▃▄█▁ | -311.0 | -161.0 | -280.0 | -225.0 | -223.0 | -220.0 | -203.0 | -191.0 | -215.0 | -140.0 | -215.0 | -215.0 | -27.0 | -360.0 | -147.0 | 60.0 | -163.0 | -144.0 | -137.0 | -144.0 | -197.0 | -150.0 | -120.0 | -182.0 | -163.0 | 146.0 | -343.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:PepcoHoldingsLLC | ▂▆▃▆▄▃▃▃█▁▅▄▅ | -385.0 | -309.0 | -375.0 | -307.0 | -339.0 | -357.0 | -359.0 | -369.0 | -258.0 | -407.0 | -320.0 | -347.0 | -323.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:PotomacElectricPowerCompany | ▁█▁▆▄▅▄▅▆▄▅▅▅▃▅▄▆▆▅▆ | -305.0 | -29.0 | -298.0 | -118.0 | -192.0 | -143.0 | -187.0 | -158.0 | -127.0 | -191.0 | -146.0 | -149.0 | -144.0 | -212.0 | -128.0 | -171.0 | -120.0 | -109.0 | -135.0 | -113.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities | ▁▃▆▃▂▃▃▂▃▃▃▃▅▃▃▃▂▅█▃▂▄▃▃▂▃▃ | -1349.0 | -268.0 | 1865.0 | 255.0 | -317.0 | 275.0 | 250.0 | -449.0 | 264.0 | 16.0 | -282.0 | -201.0 | 1184.0 | -60.0 | -218.0 | -64.0 | -572.0 | 1689.0 | 3505.0 | 208.0 | -476.0 | 698.0 | 38.0 | 151.0 | -560.0 | 18.0 | -182.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:AtlanticCityElectricCompany | ▄▆▄▁▇▆▃▇▃▄▂▄▂▁▂█▃▂▆▃ | 28.0 | 75.0 | 34.0 | -44.0 | 93.0 | 66.0 | -11.0 | 94.0 | 11.0 | 18.0 | -15.0 | 22.0 | -20.0 | -52.0 | -26.0 | 127.0 | 11.0 | -18.0 | 64.0 | -6.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▆▆▄▆▅▄▅▅▄▆▄▃▄▂█▄▅▄▄▃▅▄▄▄▅▁▇ | 195.0 | 215.0 | 4.0 | 211.0 | 67.0 | 15.0 | 128.0 | 38.0 | -84.0 | 134.0 | -12.0 | -101.0 | 1.0 | -307.0 | 404.0 | -32.0 | 80.0 | 12.0 | -82.0 | -172.0 | 64.0 | -55.0 | -38.0 | -56.0 | 58.0 | -365.0 | 264.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:CommonwealthEdisonCo | ▃▄█▄▄▆▅▄▆▄▆▄▆▄▁▇▅▄▄▆▄▄▄▆▄▄▄ | -245.0 | -1.0 | 857.0 | 21.0 | -86.0 | 349.0 | 130.0 | -1.0 | 407.0 | -23.0 | 451.0 | 2.0 | 359.0 | 22.0 | -707.0 | 558.0 | 182.0 | 56.0 | -85.0 | 314.0 | 52.0 | 3.0 | -40.0 | 344.0 | -21.0 | -57.0 | -25.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:DelmarvaPowerandLightCompany | ▂▆▂▂▃▁▂█▁▇▃▃▁▆▃▄▄▃▄▃ | -27.0 | 93.0 | -11.0 | -16.0 | 4.0 | -36.0 | -19.0 | 133.0 | -45.0 | 106.0 | 1.0 | 1.0 | -44.0 | 81.0 | 16.0 | 38.0 | 27.0 | 18.0 | 28.0 | 7.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:ExelonGenerationCoLLC | ▃▁█▅▅▅▅▅▆▅▄▅█▅▅▅▆▇▄▆▅▇▄▆▆▆▆ | -1158.0 | -1993.0 | 773.0 | -306.0 | -284.0 | -376.0 | -302.0 | -461.0 | -57.0 | -284.0 | -655.0 | -224.0 | 582.0 | -233.0 | -266.0 | -603.0 | -58.0 | 476.0 | -711.0 | -186.0 | -237.0 | 381.0 | -752.0 | 71.0 | -133.0 | -30.0 | -134.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:PecoEnergyCo | ▄█▇▇▅▆▆▄▄▄█▄▄▁▇▄█▅▄▅▁█▄▄▁█▃ | -69.0 | 262.0 | 146.0 | 209.0 | -39.0 | 55.0 | 49.0 | -47.0 | -53.0 | -71.0 | 265.0 | -72.0 | -72.0 | -340.0 | 217.0 | -71.0 | 223.0 | -42.0 | -92.0 | -6.0 | -327.0 | 239.0 | -82.0 | -80.0 | -356.0 | 254.0 | -175.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:PepcoHoldingsLLC | ▄▆▄▁▆▃▂█▃▅▁▆▄ | 73.0 | 182.0 | 60.0 | -107.0 | 166.0 | 33.0 | -38.0 | 311.0 | -13.0 | 145.0 | -84.0 | 179.0 | 66.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:PotomacElectricPowerCompany | ▆▃▇▁▆▄▃▅▃▄▁▇▆▂▂▇▂▃▂█ | 137.0 | -15.0 | 176.0 | -90.0 | 102.0 | 55.0 | -15.0 | 89.0 | 9.0 | 20.0 | -75.0 | 160.0 | 114.0 | -28.0 | -36.0 | 167.0 | -45.0 | -11.0 | -41.0 | 200.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease | ▂▄▄▄▂▂▄▃▃▂▃▃▃▁▃▄▂▄█▃▁▄▃▂▃▃▃ | -200.0 | 688.0 | 870.0 | 1000.0 | -136.0 | -467.0 | 1293.0 | -71.0 | -91.0 | -305.0 | 667.0 | -73.0 | -26.0 | -1262.0 | 250.0 | 687.0 | -763.0 | 1251.0 | 4189.0 | -53.0 | -885.0 | 1401.0 | 448.0 | -695.0 | -35.0 | 653.0 | 219.0 |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:AtlanticCityElectricCompany | ▆▆▅▆▅▆▆▅▆▆▆▂▂▁▇█▆▆▆▆ | 5.0 | -1.0 | -5.0 | 8.0 | -5.0 | -2.0 | 6.0 | -6.0 | 6.0 | -3.0 | -2.0 | -47.0 | -47.0 | -64.0 | 14.0 | 29.0 | -1.0 | 1.0 | -3.0 | 4.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▆▇▅▆▅▅▆▅▅▅▅▅▅▂█▅▅▅▅▅▅▅▅▅▅▁█ | 131.0 | 184.0 | -13.0 | 122.0 | -7.0 | 3.0 | 108.0 | -16.0 | 6.0 | -12.0 | 17.0 | 1.0 | -12.0 | -318.0 | 336.0 | 0.0 | -18.0 | 3.0 | -17.0 | -23.0 | 37.0 | 12.0 | -8.0 | -8.0 | 24.0 | -450.0 | 342.0 |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:CommonwealthEdisonCo | ▃▄▇▅▅▄▅▄▅▄▆▄▄▅▁█▅▄▄▅▅▄▄▄▄▄▅ | -216.0 | -109.0 | 430.0 | 55.0 | 38.0 | -52.0 | 137.0 | -19.0 | 18.0 | -181.0 | 218.0 | 8.0 | -25.0 | 12.0 | -692.0 | 715.0 | 16.0 | 0.0 | -57.0 | 42.0 | 22.0 | 6.0 | -3.0 | 5.0 | 2.0 | -59.0 | 63.0 |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:DelmarvaPowerandLightCompany | ▃▃▂▃▂▂▁█▃▃▂▁▂▄▂▃▃▃▃▃ | 20.0 | -1.0 | -6.0 | 7.0 | -4.0 | -16.0 | -31.0 | 134.0 | 5.0 | -1.0 | -3.0 | -38.0 | -2.0 | 42.0 | -11.0 | 12.0 | 0.0 | -1.0 | -1.0 | 3.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:ExelonGenerationCoLLC | ▄▂▆▆▄▃▇▃▅▄▄▃▄▄▄▄▃▄▄▃▂█▃▁▅▇▄ | 87.0 | -335.0 | 522.0 | 448.0 | 21.0 | -227.0 | 789.0 | -187.0 | 183.0 | 56.0 | 95.0 | -135.0 | 110.0 | -85.0 | 2.0 | -4.0 | -114.0 | 89.0 | -76.0 | -248.0 | -531.0 | 1006.0 | -261.0 | -692.0 | 330.0 | 706.0 | -3.0 |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:PecoEnergyCo | ▃▇▄▆▄▄▅▄▂▄▆▄▄▁▆▅▆▄▄▄▂▆▄▃▁█▂ | -138.0 | 349.0 | 11.0 | 204.0 | -21.0 | -88.0 | 84.0 | -3.0 | -249.0 | -59.0 | 285.0 | 17.0 | -35.0 | -453.0 | 313.0 | 190.0 | 263.0 | 6.0 | -12.0 | 8.0 | -316.0 | 253.0 | -5.0 | -119.0 | -392.0 | 553.0 | -246.0 |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:PepcoHoldingsLLC | █▄▂▅▄▁▃█▄▁▄▅▂ | 158.0 | -12.0 | -83.0 | 44.0 | 17.0 | -95.0 | -39.0 | 150.0 | 8.0 | -107.0 | -12.0 | 41.0 | -63.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CashAndCashEquivalentsPeriodIncreaseDecrease dei:LegalEntity exc:PotomacElectricPowerCompany | █▄▄▄▅▄▃▅▅▁▄█▄▂▄▇▄▄▁█ | 106.0 | 1.0 | -12.0 | 0.0 | 6.0 | -7.0 | -33.0 | 32.0 | 8.0 | -112.0 | -2.0 | 111.0 | -1.0 | -93.0 | -25.0 | 103.0 | -5.0 | -12.0 | -104.0 | 120.0 | NA | NA | NA | NA | NA | NA | NA |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:DepreciationDepletionAndAmortization | █▁▁▃▃▃▄▃▃ | 1289.0 | 1001.0 | 1021.0 | 1083.0 | 1079.0 | 1075.0 | 1105.0 | 1088.0 | 1091.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:IncreaseDecreaseInInventories | ▆▆▄▆▆▃▆▆▃▅▆▇▃▅▆▆▆▆▇▁▆▇█▄▅▆▇ | 53.0 | 95.0 | -81.0 | 113.0 | 109.0 | -128.0 | 84.0 | 107.0 | -167.0 | -15.0 | 64.0 | 132.0 | -109.0 | 14.0 | 68.0 | 53.0 | 61.0 | 94.0 | 132.0 | -291.0 | 64.0 | 166.0 | 230.0 | -80.0 | -3.0 | 85.0 | 119.0 |
| us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet | █▇▃▂▃▄▂▁▄▂▂▂▃▂▁▃▁▄▁▁▂▃▂▃▁▂▂ | 1614.0 | 1321.0 | 488.0 | 109.0 | 383.0 | 587.0 | 198.0 | -54.0 | 495.0 | 144.0 | 66.0 | 42.0 | 439.0 | 84.0 | -56.0 | 282.0 | -93.0 | 694.0 | -99.0 | -115.0 | 22.0 | 256.0 | 2.0 | 278.0 | -137.0 | 168.0 | 100.0 |
| us-gaap:NetCashProvidedByUsedInOperatingActivities | ▄▄▃▇▅▃▇▆▄▅▇▅▃▃▇█▅▅▇▄▃▅▄▁▅▆▄ | 1542.0 | 1600.0 | 1080.0 | 2501.0 | 1854.0 | 1044.0 | 2806.0 | 2367.0 | 1502.0 | 1803.0 | 2779.0 | 1697.0 | 1201.0 | 1082.0 | 2810.0 | 3080.0 | 1942.0 | 1705.0 | 2479.0 | 1490.0 | 814.0 | 1892.0 | 1586.0 | 165.0 | 1949.0 | 2056.0 | 1479.0 |
| us-gaap:NetIncomeLoss dei:LegalEntity exc:ExelonGenerationCoLLC | ▂▃▂▂▂▃▂▂▂█▃▁▃▂▂▂ | 49.0 | 476.0 | 45.0 | 257.0 | 108.0 | 363.0 | 234.0 | 178.0 | 136.0 | 2224.0 | 305.0 | -250.0 | 423.0 | -42.0 | 236.0 | -8.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ProfitLoss | ▃▃▂▄▃▄▄▃▃█▄▁▅▂▃▂▂▃▃▄▁▅▃▁▃▄▃ | 569.0 | 574.0 | 376.0 | 760.0 | 494.0 | 966.0 | 800.0 | 542.0 | 636.0 | 1938.0 | 867.0 | 64.0 | 981.0 | 248.0 | 526.0 | 306.0 | 309.0 | 587.0 | 633.0 | 738.0 | 18.0 | 1074.0 | 557.0 | 93.0 | 495.0 | 736.0 | 497.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:NetCashProvidedByUsedInInvestingActivities | █▇▂▃▄▃▃▂▃▂▃▄▁▁▁▁▂▂▃▃▅▅▅▆▄▄▆ | -393.0 | -644.0 | -2075.0 | -1756.0 | -1673.0 | -1786.0 | -1763.0 | -1989.0 | -1857.0 | -2124.0 | -1830.0 | -1569.0 | -2411.0 | -2284.0 | -2342.0 | -2329.0 | -2133.0 | -2143.0 | -1795.0 | -1751.0 | -1223.0 | -1189.0 | -1176.0 | -1011.0 | -1424.0 | -1421.0 | -1078.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:AtlanticCityElectricCompany | ▃▆▄▆▄▁▆▃▇▇▇▅▅▅▇▇▅▆▅█ | -103.0 | -78.0 | -95.0 | -73.0 | -99.0 | -128.0 | -76.0 | -108.0 | -64.0 | -69.0 | -68.0 | -88.0 | -85.0 | -82.0 | -67.0 | -60.0 | -90.0 | -76.0 | -87.0 | -53.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▁▂▁▁▂▃▃▄▄▂▄▄▅▁▃▅▅▄▇▇▇▆▇▅▆▆█ | -286.0 | -263.0 | -289.0 | -300.0 | -281.0 | -257.0 | -231.0 | -205.0 | -223.0 | -263.0 | -203.0 | -202.0 | -181.0 | -296.0 | -239.0 | -184.0 | -184.0 | -216.0 | -143.0 | -132.0 | -142.0 | -148.0 | -145.0 | -187.0 | -162.0 | -152.0 | -103.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:CommonwealthEdisonCo | ▇▇▇█▇▇▇▇▇▇▇▇▇▆▇▁▆▇▇▇▇██████ | -550.0 | -532.0 | -501.0 | -444.0 | -452.0 | -492.0 | -509.0 | -486.0 | -523.0 | -565.0 | -565.0 | -637.0 | -529.0 | -766.0 | -606.0 | -1939.0 | -716.0 | -602.0 | -521.0 | -523.0 | -507.0 | -417.0 | -401.0 | -330.0 | -345.0 | -349.0 | -357.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:DelmarvaPowerandLightCompany | █▁▄▅▅▅▅▄▆▁▄▃▅▅▆▄▄▄▅▇ | -39.0 | -143.0 | -99.0 | -85.0 | -81.0 | -78.0 | -88.0 | -100.0 | -65.0 | -136.0 | -102.0 | -111.0 | -80.0 | -82.0 | -74.0 | -99.0 | -105.0 | -92.0 | -87.0 | -61.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:ExelonGenerationCoLLC | ██▂▄▃▃▄▂▃▃▃▄▁▃▁▂▁▁▂▂▄▃▃▃▂▂▃ | 1163.0 | 997.0 | -871.0 | -291.0 | -541.0 | -433.0 | -257.0 | -934.0 | -615.0 | -689.0 | -546.0 | -145.0 | -1212.0 | -573.0 | -1068.0 | -1006.0 | -1049.0 | -1170.0 | -951.0 | -899.0 | -336.0 | -417.0 | -420.0 | -594.0 | -767.0 | -771.0 | -513.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:PecoEnergyCo | ▂▄▂▃▃▃▃▃▃▄▃▃▆▁▄▇▄▄▄▄▃▄▄▃▄█▁ | -311.0 | -161.0 | -280.0 | -225.0 | -223.0 | -220.0 | -203.0 | -191.0 | -215.0 | -140.0 | -215.0 | -215.0 | -27.0 | -360.0 | -147.0 | 60.0 | -163.0 | -144.0 | -137.0 | -144.0 | -197.0 | -150.0 | -120.0 | -182.0 | -163.0 | 146.0 | -343.0 |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:PepcoHoldingsLLC | ▂▆▃▆▄▃▃▃█▁▅▄▅ | -385.0 | -309.0 | -375.0 | -307.0 | -339.0 | -357.0 | -359.0 | -369.0 | -258.0 | -407.0 | -320.0 | -347.0 | -323.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity exc:PotomacElectricPowerCompany | ▁█▁▆▄▅▄▅▆▄▅▅▅▃▅▄▆▆▅▆ | -305.0 | -29.0 | -298.0 | -118.0 | -192.0 | -143.0 | -187.0 | -158.0 | -127.0 | -191.0 | -146.0 | -149.0 | -144.0 | -212.0 | -128.0 | -171.0 | -120.0 | -109.0 | -135.0 | -113.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:PaymentsToAcquirePropertyPlantAndEquipment | ▅▅▆▅▅▆▅▆▆▇▅▅▇▇▆█▇▆▄▅▆▄▂▂▄▃▁ | 1833.0 | 1757.0 | 2016.0 | 1687.0 | 1702.0 | 1873.0 | 1690.0 | 1927.0 | 1880.0 | 2028.0 | 1711.0 | 1731.0 | 2114.0 | 2185.0 | 1879.0 | 2287.0 | 2181.0 | 1983.0 | 1676.0 | 1784.0 | 1963.0 | 1613.0 | 1284.0 | 1217.0 | 1508.0 | 1369.0 | 1071.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:NetCashProvidedByUsedInFinancingActivities | ▁▃▆▃▂▃▃▂▃▃▃▃▅▃▃▃▂▅█▃▂▄▃▃▂▃▃ | -1349.0 | -268.0 | 1865.0 | 255.0 | -317.0 | 275.0 | 250.0 | -449.0 | 264.0 | 16.0 | -282.0 | -201.0 | 1184.0 | -60.0 | -218.0 | -64.0 | -572.0 | 1689.0 | 3505.0 | 208.0 | -476.0 | 698.0 | 38.0 | 151.0 | -560.0 | 18.0 | -182.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:AtlanticCityElectricCompany | ▄▆▄▁▇▆▃▇▃▄▂▄▂▁▂█▃▂▆▃ | 28.0 | 75.0 | 34.0 | -44.0 | 93.0 | 66.0 | -11.0 | 94.0 | 11.0 | 18.0 | -15.0 | 22.0 | -20.0 | -52.0 | -26.0 | 127.0 | 11.0 | -18.0 | 64.0 | -6.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:BaltimoreGasAndElectricCompany | ▆▆▄▆▅▄▅▅▄▆▄▃▄▂█▄▅▄▄▃▅▄▄▄▅▁▇ | 195.0 | 215.0 | 4.0 | 211.0 | 67.0 | 15.0 | 128.0 | 38.0 | -84.0 | 134.0 | -12.0 | -101.0 | 1.0 | -307.0 | 404.0 | -32.0 | 80.0 | 12.0 | -82.0 | -172.0 | 64.0 | -55.0 | -38.0 | -56.0 | 58.0 | -365.0 | 264.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:CommonwealthEdisonCo | ▃▄█▄▄▆▅▄▆▄▆▄▆▄▁▇▅▄▄▆▄▄▄▆▄▄▄ | -245.0 | -1.0 | 857.0 | 21.0 | -86.0 | 349.0 | 130.0 | -1.0 | 407.0 | -23.0 | 451.0 | 2.0 | 359.0 | 22.0 | -707.0 | 558.0 | 182.0 | 56.0 | -85.0 | 314.0 | 52.0 | 3.0 | -40.0 | 344.0 | -21.0 | -57.0 | -25.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:DelmarvaPowerandLightCompany | ▂▆▂▂▃▁▂█▁▇▃▃▁▆▃▄▄▃▄▃ | -27.0 | 93.0 | -11.0 | -16.0 | 4.0 | -36.0 | -19.0 | 133.0 | -45.0 | 106.0 | 1.0 | 1.0 | -44.0 | 81.0 | 16.0 | 38.0 | 27.0 | 18.0 | 28.0 | 7.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:ExelonGenerationCoLLC | ▃▁█▅▅▅▅▅▆▅▄▅█▅▅▅▆▇▄▆▅▇▄▆▆▆▆ | -1158.0 | -1993.0 | 773.0 | -306.0 | -284.0 | -376.0 | -302.0 | -461.0 | -57.0 | -284.0 | -655.0 | -224.0 | 582.0 | -233.0 | -266.0 | -603.0 | -58.0 | 476.0 | -711.0 | -186.0 | -237.0 | 381.0 | -752.0 | 71.0 | -133.0 | -30.0 | -134.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:PecoEnergyCo | ▄█▇▇▅▆▆▄▄▄█▄▄▁▇▄█▅▄▅▁█▄▄▁█▃ | -69.0 | 262.0 | 146.0 | 209.0 | -39.0 | 55.0 | 49.0 | -47.0 | -53.0 | -71.0 | 265.0 | -72.0 | -72.0 | -340.0 | 217.0 | -71.0 | 223.0 | -42.0 | -92.0 | -6.0 | -327.0 | 239.0 | -82.0 | -80.0 | -356.0 | 254.0 | -175.0 |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:PepcoHoldingsLLC | ▄▆▄▁▆▃▂█▃▅▁▆▄ | 73.0 | 182.0 | 60.0 | -107.0 | 166.0 | 33.0 | -38.0 | 311.0 | -13.0 | 145.0 | -84.0 | 179.0 | 66.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity exc:PotomacElectricPowerCompany | ▆▃▇▁▆▄▃▅▃▄▁▇▆▂▂▇▂▃▂█ | 137.0 | -15.0 | 176.0 | -90.0 | 102.0 | 55.0 | -15.0 | 89.0 | 9.0 | 20.0 | -75.0 | 160.0 | 114.0 | -28.0 | -36.0 | 167.0 | -45.0 | -11.0 | -41.0 | 200.0 | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ProceedsFromIssuanceOfLongTermDebt | ▁▇▅▂▂▂▃▂▃▂▃▁▂▁▃▆▂▁█▃▁▃▃▂▁▃▂ | 230.0 | 3874.0 | 2652.0 | 726.0 | 448.0 | 402.0 | 1176.0 | 358.0 | 1130.0 | 854.0 | 1635.0 | 218.0 | 763.0 | 228.0 | 1314.0 | 3023.0 | 800.0 | 2.0 | 4701.0 | 1206.0 | 251.0 | 1112.0 | 1150.0 | 950.0 | 24.0 | 1522.0 | 360.0 |
| us-gaap:RepaymentsOfLongTermDebt | ▄█▃▁▁▂▁▁▄▃▃▃▁▃▃▁▃▁▄▂▂▁▁▄▂▂▂ | 1264.0 | 2862.0 | 1032.0 | 70.0 | 222.0 | 352.0 | 171.0 | 68.0 | 1241.0 | 762.0 | 679.0 | 984.0 | 65.0 | 992.0 | 727.0 | 101.0 | 942.0 | 37.0 | 1128.0 | 580.0 | 331.0 | 23.0 | 41.0 | 1150.0 | 433.0 | 540.0 | 615.0 |
| us-gaap:PaymentsOfDividendsCommonStock | ███▇▇▇▅▅▅▄▄▄▃▃▃▃▂▂▁▁▁▁▁▁▁▁▁ | 373.0 | 373.0 | 373.0 | 351.0 | 352.0 | 352.0 | 333.0 | 333.0 | 333.0 | 315.0 | 314.0 | 304.0 | 303.0 | 293.0 | 291.0 | 295.0 | 286.0 | 282.0 | 268.0 | 269.0 | 266.0 | 266.0 | 267.0 | 266.0 | 268.0 | 265.0 | 266.0 |
| 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 |
|---|
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 19454 | 19412 | 19373 | 19362 | 19336 | 19303 | 19274 | 19238 | 19209 | 19171 | 19116 | 19063 | 19008 | 18973 | 18964 | 18862 | 18860 | 18807 | 18794 | 18756 | 18722 | 18686 | 18676 | 18647 | 16755 | 16731 | 16709 | 16679 | 16651 | 16751 | 16741 | 16716 | 16693 | 16652 | 16632 | 16594 | 16559 | 16512 | 9107 | 9077 | 9054 | 9032 | 9006 | 8923 |
| Percentage of CommonStockValue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 15.0 | 14.9 | 15.0 | 15.2 | 15.3 | 15.5 | 15.4 | 15.7 | 15.8 | 15.8 | 16.0 | 16.0 | 16.2 | 16.2 | 16.3 | 15.9 | 16.1 | 16.1 | 16.4 | 16.4 | 16.6 | 16.7 | 19.6 | 19.6 | 18.2 | 19.1 | 19.2 | 19.6 | 19.9 | 21.1 | 20.9 | 21.0 | 21.3 | 21.3 | 21.2 | 21.2 | 21.4 | 21.3 | 16.5 | 16.8 | 17.4 | 17.6 | 17.2 | 18.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 1574 | 1574 | 1271 | 1271 | 1270 | 1155 | 1154 | 1134 | 1134 | 984 | 979 | 912 | 912 | 912 | 912 | 912 | 912 | 912 | 912 | 912 | 912 | 773 | 773 |
| Percentage of CommonStockValue | 8.1 | 8.1 | 6.6 | 6.6 | 6.6 | 6.0 | 6.0 | 5.9 | 5.9 | 5.1 | 5.1 | 4.8 | 4.8 | 4.8 | 4.8 | 4.8 | 4.8 | 4.8 | 4.9 | 4.9 | 4.9 | 4.1 | 4.1 |
| Percentage of Assets | 1.2 | 1.2 | 1.0 | 1.0 | 1.0 | 0.9 | 0.9 | 0.9 | 0.9 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.7 | 0.8 |
| Percentage of Assets exc:AtlanticCityElectricCompany | 35.2 | 33.6 | 29.7 | 30.3 | 31.1 | 29.0 | 29.3 | 29.0 | 29.2 | 26.0 | 26.5 | 24.7 | 25.2 | 25.8 | 26.5 | 26.0 | 26.2 | 26.4 | 26.4 | 26.0 | 26.4 | 22.8 | 22.8 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 |
| Value | 2318 | 2318 | 2318 | 2191 | 1933 | 1907 | 1907 | 1818 | 1714 | 1714 | 1714 | 1623 | 1605 | 1605 | 1605 | 1498 | 1421 | 1421 | 1421 | 1388 | 1381 | 1381 | 1367 | 1366 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1360 | 1294 | 1294 |
| Percentage of CommonStockValue | 11.9 | 11.9 | 12.0 | 11.3 | 10.0 | 9.9 | 9.9 | 9.5 | 8.9 | 8.9 | 9.0 | 8.5 | 8.4 | 8.5 | 8.5 | 7.9 | 7.5 | 7.6 | 7.6 | 7.4 | 7.4 | 7.4 | 7.3 | 7.3 | 8.1 | 8.1 | 8.1 | 8.2 | 8.2 | 8.1 | 8.1 | 8.1 | 8.1 | 8.2 | 8.2 | 8.2 | 8.2 | 7.8 | 14.2 |
| Percentage of Assets | 1.8 | 1.8 | 1.8 | 1.7 | 1.5 | 1.5 | 1.5 | 1.5 | 1.4 | 1.4 | 1.4 | 1.4 | 1.4 | 1.4 | 1.4 | 1.3 | 1.2 | 1.2 | 1.2 | 1.2 | 1.2 | 1.2 | 1.4 | 1.4 | 1.5 | 1.6 | 1.6 | 1.6 | 1.6 | 1.7 | 1.7 | 1.7 | 1.7 | 1.7 | 1.7 | 1.7 | 1.8 | 1.7 | 2.3 |
| Percentage of Assets exc:BaltimoreGasAndElectricCompany | 19.0 | 19.7 | 19.9 | 19.3 | 17.5 | 17.7 | 17.9 | 17.6 | 17.1 | 17.2 | 17.6 | 17.0 | 17.4 | 17.5 | 17.6 | 16.8 | 16.2 | 16.1 | 16.3 | 15.7 | 16.6 | 16.5 | 16.5 | 16.8 | 17.0 | 16.7 | 16.8 | 17.2 | 17.3 | 17.1 | 17.3 | 17.8 | 17.1 | 17.8 | 18.1 | 18.1 | 18.9 | 17.6 | 18.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 1209 | 1209 | 1089 | 1089 | 1083 | 983 | 977 | 914 | 914 | 914 | 914 | 914 | 914 | 764 | 764 | 764 | 764 | 764 | 764 | 725 | 725 | 612 | 612 |
| Percentage of CommonStockValue | 6.2 | 6.2 | 5.6 | 5.6 | 5.6 | 5.1 | 5.1 | 4.8 | 4.8 | 4.8 | 4.8 | 4.8 | 4.8 | 4.0 | 4.0 | 4.1 | 4.1 | 4.1 | 4.1 | 3.9 | 3.9 | 3.3 | 3.3 |
| Percentage of Assets | 0.9 | 0.9 | 0.8 | 0.9 | 0.9 | 0.8 | 0.8 | 0.7 | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 | 0.7 | 0.7 | 0.6 | 0.7 | 0.7 | 0.7 | 0.6 | 0.6 | 0.5 | 0.6 |
| Percentage of Assets exc:DelmarvaPowerandLightCompany | 23.1 | 23.1 | 21.2 | 21.8 | 21.8 | 20.3 | 20.2 | 19.3 | 19.5 | 19.6 | 19.9 | 19.9 | 20.0 | 17.4 | 17.5 | 17.9 | 18.0 | 18.2 | 18.4 | 18.0 | 18.3 | 15.5 | 15.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 3409 | 3014 | 3014 | 3014 | 2997 | 2997 | 2766 | 2752 | 2723 | 2723 | 2578 | 2560 | 2530 | 2489 | 2489 | 2489 | 2473 | 2473 | 2473 | 2473 | 2455 | 2455 | 2455 | 2455 | 2439 | 2439 | 2439 | 2439 | 2415 | 2415 | 2415 | 2388 | 2388 | 2388 | 2388 | 2379 | 2379 | 2379 | 2379 | 2379 | 2361 | 2361 | 2361 | 2318 |
| Percentage of CommonStockValue | 17.5 | 15.5 | 15.6 | 15.6 | 15.5 | 15.5 | 14.4 | 14.3 | 14.2 | 14.2 | 13.5 | 13.4 | 13.3 | 13.1 | 13.1 | 13.2 | 13.1 | 13.1 | 13.2 | 13.2 | 13.1 | 13.1 | 13.1 | 13.2 | 14.6 | 14.6 | 14.6 | 14.6 | 14.5 | 14.4 | 14.4 | 14.3 | 14.3 | 14.3 | 14.4 | 14.3 | 14.4 | 14.4 | 26.1 | 26.2 | 26.1 | 26.1 | 26.2 | 26.0 |
| Percentage of Assets | 2.6 | 2.3 | 2.3 | 2.4 | 2.4 | 2.4 | 2.2 | 2.2 | 2.2 | 2.2 | 2.2 | 2.1 | 2.2 | 2.1 | 2.1 | 2.1 | 2.1 | 2.1 | 2.2 | 2.2 | 2.2 | 2.2 | 2.6 | 2.6 | 2.6 | 2.8 | 2.8 | 2.9 | 2.9 | 3.0 | 3.0 | 3.0 | 3.0 | 3.1 | 3.0 | 3.0 | 3.1 | 3.1 | 4.3 | 4.4 | 4.5 | 4.6 | 4.5 | 4.7 |
| Percentage of Assets exc:PecoEnergyCo | 25.3 | 23.3 | 24.1 | 24.4 | 24.7 | 26.0 | 24.1 | 24.2 | 24.8 | 24.9 | 24.2 | 24.1 | 24.5 | 24.4 | 24.5 | 21.7 | 22.4 | 22.6 | 22.8 | 22.4 | 23.2 | 23.5 | 23.7 | 24.4 | 24.1 | 24.0 | 24.5 | 24.3 | 24.7 | 24.7 | 25.1 | 24.5 | 25.4 | 25.2 | 25.5 | 24.6 | 25.8 | 25.8 | 26.0 | 25.5 | 26.2 | 26.5 | 26.3 | 25.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 2196 | 2196 | 2058 | 2058 | 1933 | 1933 | 1796 | 1765 | 1765 | 1650 | 1636 | 1555 | 1555 | 1470 | 1470 | 1470 | 1470 | 1309 | 1309 | 1309 | 1309 | 1122 | 1122 |
| Percentage of CommonStockValue | 11.3 | 11.3 | 10.6 | 10.6 | 10.0 | 10.0 | 9.3 | 9.2 | 9.2 | 8.6 | 8.6 | 8.2 | 8.2 | 7.7 | 7.8 | 7.8 | 7.8 | 7.0 | 7.0 | 7.0 | 7.0 | 6.0 | 6.0 |
| Percentage of Assets | 1.7 | 1.7 | 1.6 | 1.6 | 1.5 | 1.6 | 1.4 | 1.4 | 1.5 | 1.4 | 1.4 | 1.3 | 1.3 | 1.3 | 1.3 | 1.2 | 1.3 | 1.1 | 1.1 | 1.1 | 1.2 | 1.0 | 1.2 |
| Percentage of Assets exc:PotomacElectricPowerCompany | 22.9 | 23.1 | 22.2 | 22.3 | 21.8 | 21.9 | 20.7 | 20.5 | 20.6 | 19.6 | 19.7 | 19.0 | 19.1 | 18.6 | 18.8 | 18.9 | 19.2 | 17.6 | 17.8 | 18.1 | 18.4 | 16.3 | 16.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | 19373 | 19274 | 19116 |
| Percentage of CommonStockValue | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 15.0 | 15.4 | 16.0 |
| Percentage of Assets srt:ParentCompany | 38.3 | 39.0 | 40.3 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2013-12-31 | 2012-12-31 | 2011-12-31 |
| Value | 979 | 979 | 977 | 977 | 976 | 976 | 974 | 973 | 973 | 972786 | 970 | 968 | 967 | 967 | 965 | 962 | 961 | 960 | 958 | 958 | 957 | 956 | 954 | 954 | 896 | 895 | 894 | 894 | 892 | 889 | 698 |
| Percentage of SharesIssued | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-03-31 | 2015-12-31 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2011-01-31 | 2010-12-31 | 2009-12-31 |
| Value | 978 | 977 | 976 | 976 | 975 | 974 | 973 | 972 | 972 | 970 | 968 | 967 | 965 | 965 | 963 | 960 | 960 | 926 | 924 | 858 | 919 | 861 | 861 | 859 | 893 | 858 | 857 | 856 | 856 | 855 | 854 | 854 | 853 | 852 | 663 | 663 | 663 | 662 | 661 | 661 | 659 |
| Percentage of CommonStockSharesOutstanding | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 9.0 | 9.0 | 8.546017 | 8.546017 | 8.546017 |
| Percentage of CommonStockSharesOutstanding | 0.9 | 0.9 | 0.9 | 0.9 | 0.9 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 127 | 127 | 127 | 127 | 127 |
| Percentage of CommonStockSharesOutstanding | 13.0 | 13.1 | 13.1 | 13.2 | 13.7 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 170 | 170 | 170 | 170 | 170 |
| Percentage of CommonStockSharesOutstanding | 17.4 | 17.5 | 17.6 | 17.7 | 18.4 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 976 | 973 |
| Percentage of CommonStockSharesOutstanding | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 979 | 977 | 977 | 976 | 976 | 974 | 974 | 972 | 970 | 969 | 968 | 967 | 965 | 936 | 930 | 928 | 927 | 926 | 925 | 924 | 915 | 866 | 867 | 868 | 863 | 864 | 861 | 860 | 860 | 860 | 855 | 857 | 857 | 856 | 707 | 666 | 665 | 664 | 664 | 663 | 663 | 662 | 662 | 662 | 662 | 661 | 661 |
| Percentage of WeightedAverageNumberOfDilutedSharesOutstanding | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 978 | 977 | 976 | 976 | 975 | 973 | 972 | 971 | 968 | 967 | 966 | 964 | 962 | 934 | 928 | 925 | 925 | 924 | 923 | 921 | 913 | 863 | 862 | 861 | 861 | 860 | 858 | 856 | 857 | 856 | 855 | 854 | 854 | 853 | 705 | 664 | 663 | 663 | 662 | 662 | 662 | 661 | 661 | 660 | 660 | 659 | 659 |
| Percentage of WeightedAverageNumberOfSharesOutstandingBasic | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2016-03-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 0.0 | 0.0 | 1.0 | 1.0 | 0.0 | 0.0 | 0.0 | 2.0 | 2.0 | 13 | 4.0 | 13 | 15 | 2.0 | 16 | 18 | 20 | 17 | 0.0 | 18 | 17 | 11 | 10.0 | 10.0 | 9.0 | 9.0 | 9.0 | 6.0 |
| Percentage of AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount | 0.0 | 0.0 | 100.0 | 100.0 | 0.0 | 0.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 0.41 | -0.3 | 0.37 | 0.51 | 0.53 | 0.6 | 0.79 | 0.79 | 0.5 | 0.93 | 0.16 | 0.76 | 0.56 | 0.61 | 1.94 | 0.86 | 0.09 | 1.07 | 0.22 | 0.53 | 0.29 | 0.19 | 0.34 | 0.69 | 0.74 | 0.8 | 0.02 | 1.15 | 0.61 | 0.1 | 0.6 | 0.86 | 0.57 | -0.01 | 0.44 | 0.35 | 0.34 | 0.28 | 0.91 | 0.91 | 0.93 | 1.01 | 0.79 | 1.28 | 0.67 | 1.13 | 0.88 | 1.15 | 1.0 | 1.08 |
| Percentage of EarningsPerShareBasic | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 0.41 | -0.3 | 0.37 | 0.51 | 0.53 | 0.6 | 0.79 | 0.79 | 0.5 | 0.93 | 0.16 | 0.76 | 0.56 | 0.6 | 1.93 | 0.85 | 0.09 | 1.07 | 0.22 | 0.53 | 0.29 | 0.19 | 0.33 | 0.69 | 0.74 | 0.8 | 0.02 | 1.15 | 0.6 | 0.1 | 0.59 | 0.86 | 0.57 | -0.01 | 0.44 | 0.35 | 0.33 | 0.28 | 0.91 | 0.9 | 0.93 | 1.01 | 0.79 | 1.27 | 0.67 | 1.13 | 0.88 | 1.14 | 0.99 | 1.08 |
| Percentage of EarningsPerShareDiluted | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 458 | -235.0 | 63 | 529 | 562 | 603 | 541 | 799 | 506 | 890 | 26 | 785 | 582 | 656 | 1973 | 868 | 115 | 985 | 46 | 562 | 337 | 151 | 263 | 619 | 683 | 749 | -672.0 | 1063 | 688 | 97 | 1115 | 748 | 497 | 95 | 22 | 205 | 175 | 451 | 696 | 570 | 509 | 694 | -71.0 | 1096 | 61 | 1143 |
| Percentage of ComprehensiveIncomeNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 52900.0 | 56200.0 | 60300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 56200.0 | 33700.0 | 0.0 | 0.0 | 30950.0 | 68300.0 | 74900.0 | 0.0 | 0.0 | 0.0 | 9700.0 | 0.0 | 37400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | -59.0 | -792.0 | 25 | 52 | 478 | 36 | 401 | 257 | 108 | 365 | -184.0 | 236 | 179 | 142 | 2214 | 309 | -249.0 | 436 | -53.0 | 275 | 28 | 256 | 129 | 319 | 396 | 468 | -65.0 | 823 | 217 | -206.0 | 236 | 453 | 194 | -121.0 | -100.0 | -65.0 | -98.0 | 420 | 796 | 261 | 189 | 425 | -18.0 | 897 | -163.0 | 1112 |
| Percentage of ComprehensiveIncomeNetOfTax | -12.9 | 337.0 | 39.7 | 9.8 | 85.1 | 6.0 | 74.1 | 32.2 | 21.3 | 41.0 | -707.7 | 30.1 | 30.8 | 21.6 | 112.2 | 35.6 | -216.5 | 44.3 | -115.2 | 48.9 | 8.3 | 169.5 | 49.0 | 51.5 | 58.0 | 62.5 | 9.7 | 77.4 | 31.5 | -212.4 | 21.2 | 60.6 | 39.0 | -127.4 | -454.5 | -31.7 | -56.0 | 93.1 | 114.4 | 45.8 | 37.1 | 61.2 | 25.4 | 81.8 | -267.2 | 97.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 5200.0 | 47800.0 | 3600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 27500.0 | 2800.0 | 0.0 | 0.0 | 15950.0 | 39600.0 | 46800.0 | 0.0 | 0.0 | 0.0 | -20600.0 | 0.0 | 22650.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | -23.2 | -268.5 | 0.0 | 15.7 | 176.4 | 10.9 | 0.0 | 93.5 | 42.9 | 115.1 | 0.0 | 76.6 | 65.6 | 35.7 | 0.0 | 104.4 | -92.9 | 132.1 | 0.0 | 54.8 | 7.8 | 95.5 | 0.0 | 154.9 | 258.8 | 221.8 | 0.0 | 734.8 | 108.0 | -61.7 | 0.0 | 118.0 | 55.1 | -30.9 | 0.0 | -13.7 | -23.3 | 113.5 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 141 | 128 | 77 | 216 | 94 | 108 | 65 | 189 | 106 | 117 | 62 | 187 | 84 | 65 | 3.0 | 153 | 66 | 140 |
| Percentage of ComprehensiveIncomeNetOfTax | 30.8 | -54.5 | 122.2 | 40.8 | 16.7 | 17.9 | 12.0 | 23.7 | 20.9 | 13.1 | 238.5 | 23.8 | 14.4 | 9.9 | 0.2 | 17.6 | 57.4 | 14.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 21600.0 | 9400.0 | 10800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 3525.0 | 4266.7 | 0.0 | 3600.0 | 3133.3 | 3600.0 | 0.0 | 4725.0 | 3533.3 | 3900.0 | 0.0 | 6233.3 | 2800.0 | 1625.0 | 0.0 | 1275.0 | 550.0 | 1166.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 |
| Value | 75 | 25 | 76 | 68 | 53 | -206.0 | 36 | -9.0 | 9.0 | 58 | -48.0 | 67 | 4.0 | 52 | 67 | 43 | -16.0 | -16.0 | 49 | 31 | 39 | -50.0 | -19.0 | -42.0 | -5.0 |
| Percentage of ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | 5300.0 | -20600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 3100.0 | 3900.0 | 0.0 | 0.0 | -2100.0 | -500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-06-30 |
| Value | 74 | 24 | 75 | 68 | 53 | -206.0 | 36 | -10.0 | 9.0 | 58 | -48.0 | 66 | 4.0 | 51 | 65 | 43 | -16.0 | -16.0 | 49 | 30 | 36 | -53.0 | -8.0 |
| Percentage of ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest | 98.7 | 96.0 | 98.7 | 100.0 | 100.0 | 100.0 | 100.0 | 111.1 | 100.0 | 100.0 | 100.0 | 98.5 | 100.0 | 98.1 | 97.0 | 100.0 | 100.0 | 100.0 | 100.0 | 96.8 | 92.3 | 106.0 | 160.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | 5300.0 | -20600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 3000.0 | 3600.0 | 0.0 | -800.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 29.1 | 8.1 | 0.0 | 20.5 | 19.6 | -62.4 | 0.0 | -3.6 | 3.6 | 18.3 | 0.0 | 21.4 | 1.5 | 12.8 | 0.0 | 14.5 | -6.0 | -4.8 | 0.0 | 6.0 | 10.1 | -19.8 | -5.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 |
| Value | 533 | -210.0 | 139 | 597 | 615 | 397 | 577 | 790 | 515 | 948 | -22.0 | 852 | 586 | 708 | 2040 | 911 | 99 | 969 | 137 | 531 | 298 | 151 | 263 | 661 | 688 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 59700.0 | 61500.0 | 39700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 53100.0 | 29800.0 | 0.0 | 0.0 | 33050.0 | 68800.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 37 | 14 | 6.0 | 75 | 18 | 13 | 12 | 63 | 14 | 10.0 | -1.0 | 61 | 8.0 | 7.0 | 0.0 | 41 | 8.0 | 28 | 8.0 | 47 | 3.0 | -100.0 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 6.9 | -6.7 | 4.3 | 12.6 | 2.9 | 3.3 | 2.1 | 8.0 | 2.7 | 1.1 | 4.5 | 7.2 | 1.4 | 1.0 | 0.0 | 4.5 | 8.1 | 2.9 | 5.8 | 8.9 | 1.0 | -66.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 7500.0 | 1800.0 | 1300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 4700.0 | 300.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 3700.0 | 1400.0 | 0.0 | 7500.0 | 1800.0 | 1300.0 | 0.0 | 6300.0 | 1400.0 | 1000.0 | 0.0 | 6100.0 | 800.0 | 700.0 | 0.0 | 0.0 | 800.0 | 2800.0 | 0.0 | 4700.0 | 300.0 | -10000.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 |
| Value | 45 | 209 | 76 | 53 | 39 | 181 | 99 | 55 | 45 | 160 | 71 | 63 | 51 | 128 | 76 | 62 | 45 | 125 | 111 | 54 | 31 | 101 | 86 | 51 | 44 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 8.4 | -99.5 | 54.7 | 8.9 | 6.3 | 45.6 | 17.2 | 7.0 | 8.7 | 16.9 | -322.7 | 7.4 | 8.7 | 18.1 | 3.7 | 6.8 | 45.5 | 12.9 | 81.0 | 10.2 | 10.4 | 66.9 | 32.7 | 7.7 | 6.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 5300.0 | 3900.0 | 18100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 5400.0 | 3100.0 | 0.0 | 0.0 | 2550.0 | 4400.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 642.9 | 3483.3 | 0.0 | 883.3 | 975.0 | 3016.7 | 0.0 | 916.7 | 750.0 | 2666.7 | 0.0 | 1050.0 | 850.0 | 2133.3 | 0.0 | 2066.7 | 1500.0 | 2500.0 | 0.0 | 771.4 | 775.0 | 2020.0 | 0.0 | 1700.0 | 4400.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 192 | 197 | 134 | 196 | -61.0 | 168 | 144 | 200 | 186 | 157 | 141 | 193 | 164 | 165 | 120 | 189 | 118 | 141 | 81 | 37 | 145 | 115 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 36.0 | -93.8 | 96.4 | 32.8 | -9.9 | 42.3 | 25.0 | 25.3 | 36.1 | 16.6 | -640.9 | 22.7 | 28.0 | 23.3 | 5.9 | 20.7 | 119.2 | 14.6 | 59.1 | 7.0 | 48.7 | 76.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 19600.0 | -6100.0 | 16800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 3700.0 | 14500.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 3840.0 | 3283.3 | 0.0 | 1306.7 | -554.5 | 3360.0 | 0.0 | 5000.0 | 3720.0 | 3925.0 | 0.0 | 4825.0 | 3280.0 | 1178.6 | 0.0 | 6300.0 | 3933.3 | 2820.0 | 0.0 | 925.0 | 4833.3 | 2300.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-03-31 | 2016-03-31 |
| Value | 30 | 56 | 34 | 27 | 19 | 45 | 31 | 33 | 30 | 53 | 30 | 33 | 26 | 31 | 14 | 31 | 57 | -72.0 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 5.6 | -26.7 | 24.5 | 4.5 | 3.1 | 11.3 | 5.4 | 4.2 | 5.8 | 5.6 | -136.4 | 3.9 | 4.4 | 4.4 | 0.7 | 3.4 | 5.9 | -47.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 2700.0 | 1900.0 | 4500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 1500.0 | 2800.0 | 0.0 | 900.0 | 950.0 | 2250.0 | 0.0 | 3300.0 | 1500.0 | 2650.0 | 0.0 | 1650.0 | 1300.0 | 1550.0 | 0.0 | 1550.0 | 2850.0 | -3600.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 |
| Value | 15 | -768.0 | 100 | 120 | 531 | -170.0 | 437 | 247 | 117 | 423 | -232.0 | 302 | 183 | 193 | 2279 | 352 | -265.0 | 420 | 22 | 245 | -8.0 | 256 | 119 | 364 | 404 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 2.8 | 365.7 | 71.9 | 20.1 | 86.3 | -42.8 | 75.7 | 31.3 | 22.7 | 44.6 | 1054.5 | 35.4 | 31.2 | 27.3 | 111.7 | 38.6 | -267.7 | 43.3 | 16.1 | 46.1 | -2.7 | 169.5 | 45.2 | 55.1 | 58.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 12000.0 | 53100.0 | -17000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 24500.0 | -800.0 | 0.0 | 0.0 | 18200.0 | 40400.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 5.9 | -260.3 | 0.0 | 36.3 | 195.9 | -51.5 | 0.0 | 89.8 | 46.4 | 133.4 | 0.0 | 98.1 | 67.0 | 48.5 | 0.0 | 118.9 | -98.9 | 127.3 | 0.0 | 48.8 | -2.2 | 95.5 | 0.0 | 176.7 | 264.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 104 | 167 | 130 | 138 | 39 | 140 | 118 | 140 | 102 | 168 | 124 | 126 | 96 | 113 | 107 | 112 | 88 | 127 | 92 | 122 | 100 | 124 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 19.5 | -79.5 | 93.5 | 23.1 | 6.3 | 35.3 | 20.5 | 17.7 | 19.8 | 17.7 | -563.6 | 14.8 | 16.4 | 16.0 | 5.2 | 12.3 | 88.9 | 13.1 | 67.2 | 23.0 | 33.6 | 82.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 13800.0 | 3900.0 | 14000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 12200.0 | 10000.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 5200.0 | 8350.0 | 0.0 | 4600.0 | 1950.0 | 7000.0 | 0.0 | 14000.0 | 5100.0 | 16800.0 | 0.0 | 6300.0 | 4800.0 | 5650.0 | 0.0 | 5600.0 | 4400.0 | 12700.0 | 0.0 | 6100.0 | 5000.0 | 12400.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 75 | 59 | 39 | 118 | 57 | 52 | 26 | 98 | 64 | 55 | 36 | 89 | 54 | 31 | 17 | 87 | 43 | 58 | 22 | 79 | 49 | -108.0 |
| Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | 14.1 | -28.1 | 28.1 | 19.8 | 9.3 | 13.1 | 4.5 | 12.4 | 12.4 | 5.8 | -163.6 | 10.4 | 9.2 | 4.4 | 0.8 | 9.5 | 43.4 | 6.0 | 16.1 | 14.9 | 16.4 | -71.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 11800.0 | 5700.0 | 5200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 7900.0 | 4900.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 7500.0 | 5900.0 | 0.0 | 3933.3 | 5700.0 | 5200.0 | 0.0 | 4900.0 | 6400.0 | 2750.0 | 0.0 | 4450.0 | 2700.0 | 1550.0 | 0.0 | 8700.0 | 4300.0 | 5800.0 | 0.0 | 7900.0 | 4900.0 | -10800.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 1666 | 1697 | 1702 | 1289 | 1001 | 1021 | 1015 | 1083 | 1079 | 1075 | 1069 | 1105 | 1088 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 128900.0 | 100100.0 | 102100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 40 | 47 | 46 | 48 | 44 | 43 | 43 | 43 | 40 | 31 | 29 | 38 | 36 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 2.4 | 2.8 | 2.7 | 3.7 | 4.4 | 4.2 | 4.2 | 4.0 | 3.7 | 2.9 | 2.7 | 3.4 | 3.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 4800.0 | 4400.0 | 4300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 4000.0 | 4700.0 | 0.0 | 4800.0 | 4400.0 | 4300.0 | 0.0 | 4300.0 | 4000.0 | 3100.0 | 0.0 | 3800.0 | 3600.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 141 | 152 | 145 | 133 | 129 | 143 | 134 | 116 | 117 | 136 | 125 | 110 | 114 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 8.5 | 9.0 | 8.5 | 10.3 | 12.9 | 14.0 | 13.2 | 10.7 | 10.8 | 12.7 | 11.7 | 10.0 | 10.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 13300.0 | 12900.0 | 14300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 2014.3 | 2533.3 | 0.0 | 2216.7 | 3225.0 | 2383.3 | 0.0 | 1933.3 | 1950.0 | 2266.7 | 0.0 | 1833.3 | 1900.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 296 | 292 | 292 | 294 | 274 | 273 | 266 | 259 | 257 | 251 | 244 | 237 | 231 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 17.8 | 17.2 | 17.2 | 22.8 | 27.4 | 26.7 | 26.2 | 23.9 | 23.8 | 23.3 | 22.8 | 21.4 | 21.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 29400.0 | 27400.0 | 27300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 5920.0 | 4866.7 | 0.0 | 1960.0 | 2490.9 | 5460.0 | 0.0 | 6475.0 | 5140.0 | 6275.0 | 0.0 | 5925.0 | 4620.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 51 | 53 | 48 | 48 | 47 | 48 | 46 | 46 | 45 | 46 | 47 | 47 | 43 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 3.1 | 3.1 | 2.8 | 3.7 | 4.7 | 4.7 | 4.5 | 4.2 | 4.2 | 4.3 | 4.4 | 4.3 | 4.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 4800.0 | 4700.0 | 4800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 2550.0 | 2650.0 | 0.0 | 1600.0 | 2350.0 | 2400.0 | 0.0 | 4600.0 | 2250.0 | 2300.0 | 0.0 | 2350.0 | 2150.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 930 | 940 | 962 | 558 | 300 | 304 | 314 | 407 | 409 | 405 | 414 | 468 | 466 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 55.8 | 55.4 | 56.5 | 43.3 | 30.0 | 29.8 | 30.9 | 37.6 | 37.9 | 37.7 | 38.7 | 42.4 | 42.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 55800.0 | 30000.0 | 30400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 366.1 | 318.6 | 0.0 | 168.6 | 110.7 | 92.1 | 0.0 | 148.0 | 162.3 | 127.8 | 0.0 | 151.9 | 170.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 87 | 86 | 88 | 85 | 88 | 86 | 86 | 83 | 83 | 81 | 77 | 75 | 74 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 5.2 | 5.1 | 5.2 | 6.6 | 8.8 | 8.4 | 8.5 | 7.7 | 7.7 | 7.5 | 7.2 | 6.8 | 6.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 8500.0 | 8800.0 | 8600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 4350.0 | 4300.0 | 0.0 | 2833.3 | 4400.0 | 4300.0 | 0.0 | 8300.0 | 4150.0 | 8100.0 | 0.0 | 3750.0 | 3700.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 194 | 210 | 197 | 200 | 191 | 194 | 192 | 193 | 188 | 180 | 185 | 192 | 180 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 11.6 | 12.4 | 11.6 | 15.5 | 19.1 | 19.0 | 18.9 | 17.8 | 17.4 | 16.7 | 17.3 | 17.4 | 16.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 20000.0 | 19100.0 | 19400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 4850.0 | 7000.0 | 0.0 | 3333.3 | 6366.7 | 6466.7 | 0.0 | 4825.0 | 6266.7 | 6000.0 | 0.0 | 6400.0 | 6000.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 96 | 102 | 95 | 96 | 92 | 95 | 93 | 95 | 93 | 94 | 99 | 99 | 92 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 5.8 | 6.0 | 5.6 | 7.4 | 9.2 | 9.3 | 9.2 | 8.8 | 8.6 | 8.7 | 9.3 | 9.0 | 8.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 9600.0 | 9200.0 | 9500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 9600.0 | 10200.0 | 0.0 | 3200.0 | 9200.0 | 9500.0 | 0.0 | 4750.0 | 9300.0 | 4700.0 | 0.0 | 4950.0 | 4600.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 21 | 20 | 20 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 1.3 | 1.2 | 1.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC exc:GenerationNewEngland | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 |
| Value | 21 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 1.3 |
| Percentage of RevenueFromRelatedParties | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationNewEngland | 0.0 |
| Period End | 2021-03-31 |
| Value | 20 |
| Percentage of CostOfGoodsAndServicesSoldDepreciationAndAmortization | 1.2 |
| Percentage of RevenueFromRelatedParties | 0.0 |
| Percentage of RevenueFromRelatedParties exc:MidwestAssetGroup | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 7561 | 10082 | 7853 | 8087 | 6769 | 7529 | 7393 | 7559 | 6881 | 8262 | 8107 | 8252 | 7138 | 8648 | 7334 | 7300 | 7392 | 7691 | 7072 | 7736 | 6294 | 7099 | 6001 | 6203 | 5387 | 7465 | 7016 | 5513 | 5456 | 7055 | 5277 | 5285 | 5115 | 5565 | 5558 | 5972 | 5183 | 4305 | 2928 | 4114 | 3553 | 3850 | 3554 | 3925 | 3380 | 3059 |
| Percentage of CostsAndExpenses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 808700.0 | 676900.0 | 752900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 773600.0 | 629400.0 | 0.0 | 0.0 | 310150.0 | 538700.0 | 746500.0 | 0.0 | 0.0 | 0.0 | 705500.0 | 0.0 | 264250.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 269 | 282 | 276 | 338 | 258 | 251 | 251 | 340 | 246 | 252 | 240 | 322 | 240 | 287 | 243 | 291 | 245 | 250 | 249 | 338 | 252 | 412 | 262 | 335 | 260 | 305 |
| Percentage of CostsAndExpenses | 3.6 | 2.8 | 3.5 | 4.2 | 3.8 | 3.3 | 3.4 | 4.5 | 3.6 | 3.1 | 3.0 | 3.9 | 3.4 | 3.3 | 3.3 | 4.0 | 3.3 | 3.3 | 3.5 | 4.4 | 4.0 | 5.8 | 4.4 | 5.4 | 4.8 | 4.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 33800.0 | 25800.0 | 25100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 33800.0 | 25200.0 | 0.0 | 0.0 | 16750.0 | 26000.0 | 30500.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 26900.0 | 28200.0 | 0.0 | 33800.0 | 25800.0 | 25100.0 | 0.0 | 34000.0 | 24600.0 | 25200.0 | 0.0 | 32200.0 | 24000.0 | 28700.0 | 0.0 | 0.0 | 24500.0 | 25000.0 | 0.0 | 33800.0 | 25200.0 | 41200.0 | 0.0 | 33500.0 | 26000.0 | 30500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | 620 | 752 | 695 | 642 | 573 | 688 | 638 | 612 | 569 | 756 | 691 | 628 | 578 | 800 | 649 | 614 | 576 | 723 | 622 | 697 | 621 | 742 | 602 | 616 | 529 | 832 | 648 | 595 | 598 | 885 | 693 | 623 | 584 | 717 | 642 | 690 | 564 | 707 | 589 | 722 | 620 | 823 |
| Percentage of CostsAndExpenses | 8.2 | 7.5 | 8.9 | 7.9 | 8.5 | 9.1 | 8.6 | 8.1 | 8.3 | 9.2 | 8.5 | 7.6 | 8.1 | 9.3 | 8.8 | 8.4 | 7.8 | 9.4 | 8.8 | 9.0 | 9.9 | 10.5 | 10.0 | 9.9 | 9.8 | 11.1 | 9.2 | 10.8 | 11.0 | 12.5 | 13.1 | 11.8 | 11.4 | 12.9 | 11.6 | 11.6 | 10.9 | 16.4 | 20.1 | 17.5 | 17.5 | 21.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 64200.0 | 57300.0 | 68800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 69700.0 | 62100.0 | 0.0 | 0.0 | 30800.0 | 52900.0 | 83200.0 | 0.0 | 0.0 | 0.0 | 88500.0 | 0.0 | 31150.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 8857.1 | 12533.3 | 0.0 | 10700.0 | 14325.0 | 11466.7 | 0.0 | 10200.0 | 9483.3 | 12600.0 | 0.0 | 10466.7 | 9633.3 | 13333.3 | 0.0 | 20466.7 | 19200.0 | 14460.0 | 0.0 | 9957.1 | 15525.0 | 14840.0 | 0.0 | 20533.3 | 52900.0 | 11885.7 | 0.0 | 19833.3 | 29900.0 | 5531.2 | 0.0 | 31150.0 | 14600.0 | 17925.0 | 0.0 | 17250.0 | 28200.0 | 23566.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 1196 | 1210 | 1152 | 1302 | 1345 | 1151 | 1149 | 1256 | 1040 | 1135 | 1131 | 1275 | 1111 | 1223 | 1023 | 1167 | 1038 | 984 | 1006 | 1109 | 962 | 980 | 979 | 1049 | 905 | 955 | 885 | 935 | 870 | 896 | 833 | 878 | 848 | 951 | 989 | 1266 | 1139 | 1162 | 1077 | 1541 | 1190 | 1266 | 1143 | 1639 | 1243 | 1124 |
| Percentage of CostsAndExpenses | 15.8 | 12.0 | 14.7 | 16.1 | 19.9 | 15.3 | 15.5 | 16.6 | 15.1 | 13.7 | 14.0 | 15.5 | 15.6 | 14.1 | 13.9 | 16.0 | 14.0 | 12.8 | 14.2 | 14.3 | 15.3 | 13.8 | 16.3 | 16.9 | 16.8 | 12.8 | 12.6 | 17.0 | 15.9 | 12.7 | 15.8 | 16.6 | 16.6 | 17.1 | 17.8 | 21.2 | 22.0 | 27.0 | 36.8 | 37.5 | 33.5 | 32.9 | 32.2 | 41.8 | 36.8 | 36.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 130200.0 | 134500.0 | 115100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 110900.0 | 96200.0 | 0.0 | 0.0 | 52450.0 | 90500.0 | 95500.0 | 0.0 | 0.0 | 0.0 | 89600.0 | 0.0 | 43900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 23920.0 | 20166.7 | 0.0 | 8680.0 | 12227.3 | 23020.0 | 0.0 | 31400.0 | 20800.0 | 28375.0 | 0.0 | 31875.0 | 22220.0 | 8735.7 | 0.0 | 38900.0 | 34600.0 | 19680.0 | 0.0 | 27725.0 | 32066.7 | 19600.0 | 0.0 | 104900.0 | 90500.0 | 95500.0 | 0.0 | 93500.0 | 0.0 | 89600.0 | 0.0 | 87800.0 | 0.0 | 95100.0 | 0.0 | 0.0 | 113900.0 | 116200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 255 | 309 | 277 | 296 | 263 | 284 | 269 | 268 | 243 | 308 | 284 | 277 | 247 | 335 | 278 | 268 | 241 | 284 | 288 | 263 | 251 | 434 | 251 | 282 | 247 | 358 |
| Percentage of CostsAndExpenses | 3.4 | 3.1 | 3.5 | 3.7 | 3.9 | 3.8 | 3.6 | 3.5 | 3.5 | 3.7 | 3.5 | 3.4 | 3.5 | 3.9 | 3.8 | 3.7 | 3.3 | 3.7 | 4.1 | 3.4 | 4.0 | 6.1 | 4.2 | 4.5 | 4.6 | 4.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 29600.0 | 26300.0 | 28400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 26300.0 | 25100.0 | 0.0 | 0.0 | 14100.0 | 24700.0 | 35800.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 12750.0 | 15450.0 | 0.0 | 9866.7 | 13150.0 | 14200.0 | 0.0 | 26800.0 | 12150.0 | 15400.0 | 0.0 | 13850.0 | 12350.0 | 16750.0 | 0.0 | 13400.0 | 12050.0 | 14200.0 | 0.0 | 13150.0 | 12550.0 | 21700.0 | 0.0 | 28200.0 | 12350.0 | 17900.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 4469 | 6672 | 4684 | 4727 | 3547 | 4400 | 4295 | 4274 | 4096 | 4963 | 5035 | 4961 | 4298 | 5218 | 4365 | 4256 | 4641 | 4731 | 4205 | 4693 | 3633 | 4324 | 4069 | 4147 | 3536 | 5120 | 5018 | 3526 | 3620 | 4760 | 3370 | 3571 | 3446 | 3588 | 3616 | 3853 | 3312 | 2445 | 1488 | 2108 | 1899 | 1938 | 1937 | 1772 | 1766 | 1505 |
| Percentage of CostsAndExpenses | 59.1 | 66.2 | 59.6 | 58.5 | 52.4 | 58.4 | 58.1 | 56.5 | 59.5 | 60.1 | 62.1 | 60.1 | 60.2 | 60.3 | 59.5 | 58.3 | 62.8 | 61.5 | 59.5 | 60.7 | 57.7 | 60.9 | 67.8 | 66.9 | 65.6 | 68.6 | 71.5 | 64.0 | 66.3 | 67.5 | 63.9 | 67.6 | 67.4 | 64.5 | 65.1 | 64.5 | 63.9 | 56.8 | 50.8 | 51.2 | 53.4 | 50.3 | 54.5 | 45.1 | 52.2 | 49.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 472700.0 | 354700.0 | 440000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 469300.0 | 363300.0 | 0.0 | 0.0 | 207350.0 | 353600.0 | 512000.0 | 0.0 | 0.0 | 0.0 | 476000.0 | 0.0 | 178550.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 1759.4 | 2261.7 | 0.0 | 1428.1 | 1308.9 | 1333.3 | 0.0 | 1554.2 | 1625.4 | 1565.6 | 0.0 | 1610.7 | 1574.4 | 1311.1 | 0.0 | 1437.8 | 1731.7 | 1433.6 | 0.0 | 934.9 | 1014.8 | 1613.4 | 0.0 | 2013.1 | 2311.1 | 2426.5 | 0.0 | 3148.2 | 1801.0 | 1425.1 | 0.0 | 929.9 | 979.0 | 915.3 | 0.0 | 814.6 | 788.6 | 660.8 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 552 | 679 | 612 | 658 | 618 | 625 | 605 | 595 | 510 | 678 | 599 | 603 | 526 | 724 | 572 | 546 | 493 | 604 | 552 | 584 | 512 | 645 | 519 | 586 | 537 | 763 | 596 | 560 | 522 | 844 | 635 | 573 | 534 | 692 | 673 | 628 | 564 | 698 | 647 | 793 | 681 | 943 | 1229 | 1280 | 1087 | 1261 |
| Percentage of CostsAndExpenses | 7.3 | 6.7 | 7.8 | 8.1 | 9.1 | 8.3 | 8.2 | 7.9 | 7.4 | 8.2 | 7.4 | 7.3 | 7.4 | 8.4 | 7.8 | 7.5 | 6.7 | 7.9 | 7.8 | 7.5 | 8.1 | 9.1 | 8.6 | 9.4 | 10.0 | 10.2 | 8.5 | 10.2 | 9.6 | 12.0 | 12.0 | 10.8 | 10.4 | 12.4 | 12.1 | 10.5 | 10.9 | 16.2 | 22.1 | 19.3 | 19.2 | 24.5 | 34.6 | 32.6 | 32.2 | 41.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 65800.0 | 61800.0 | 62500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 58400.0 | 51200.0 | 0.0 | 0.0 | 29300.0 | 53700.0 | 76300.0 | 0.0 | 0.0 | 0.0 | 84400.0 | 0.0 | 28650.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 27600.0 | 33950.0 | 0.0 | 21933.3 | 30900.0 | 31250.0 | 0.0 | 59500.0 | 25500.0 | 67800.0 | 0.0 | 30150.0 | 26300.0 | 36200.0 | 0.0 | 27300.0 | 24650.0 | 60400.0 | 0.0 | 29200.0 | 25600.0 | 64500.0 | 0.0 | 58600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 84400.0 | 0.0 | 57300.0 | 0.0 | 0.0 | 0.0 | 62800.0 | 56400.0 | 69800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 955 | 1058 | 988 | 1102 | 956 | 1000 | 978 | 1124 | 926 | 1053 | 991 | 1116 | 923 | 1125 | 964 | 1025 | 927 | 995 |
| Percentage of CostsAndExpenses | 12.6 | 10.5 | 12.6 | 13.6 | 14.1 | 13.3 | 13.2 | 14.9 | 13.5 | 12.7 | 12.2 | 13.5 | 12.9 | 13.0 | 13.1 | 14.0 | 12.5 | 12.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 110200.0 | 95600.0 | 100000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 23875.0 | 35266.7 | 0.0 | 18366.7 | 31866.7 | 33333.3 | 0.0 | 28100.0 | 30866.7 | 35100.0 | 0.0 | 37200.0 | 30766.7 | 28125.0 | 0.0 | 8541.7 | 7725.0 | 8291.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 429 | 466 | 435 | 465 | 436 | 462 | 455 | 515 | 438 | 491 | 465 | 516 | 438 | 501 | 422 | 455 | 431 | 451 | 441 | 503 | 420 | 656 | 410 | 477 | 421 | 482 |
| Percentage of CostsAndExpenses | 5.7 | 4.6 | 5.5 | 5.7 | 6.4 | 6.1 | 6.2 | 6.8 | 6.4 | 5.9 | 5.7 | 6.3 | 6.1 | 5.8 | 5.8 | 6.2 | 5.8 | 5.9 | 6.2 | 6.5 | 6.7 | 9.2 | 6.8 | 7.7 | 7.8 | 6.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 46500.0 | 43600.0 | 46200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 50300.0 | 42000.0 | 0.0 | 0.0 | 23850.0 | 42100.0 | 48200.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 42900.0 | 46600.0 | 0.0 | 15500.0 | 43600.0 | 46200.0 | 0.0 | 25750.0 | 43800.0 | 24550.0 | 0.0 | 25800.0 | 21900.0 | 25050.0 | 0.0 | 45500.0 | 43100.0 | 45100.0 | 0.0 | 50300.0 | 42000.0 | 65600.0 | 0.0 | 47700.0 | 42100.0 | 48200.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 258 | 118 | 402 | 255 | 455 | -651.0 | 196 | 63 | 96 | 308 | -324.0 | 101 | -12.0 | -68.0 | 187 | 145 | 109 | 175 | -14.0 | 129 | 59 | 55 | 90 | -223.0 | -45.0 | 47 | 69 | -27.0 | 142 | 26 | 75 | 68 | -39.0 | 66 | 15 | 72 | -33.0 | 103 | 76 | -141.0 | 11 | 40 | 56 | 108 | -95.0 | 36 |
| Percentage of GainLossOnInvestments | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 25500.0 | 45500.0 | -65100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 12900.0 | 5900.0 | 0.0 | 0.0 | -11150.0 | -4500.0 | 4700.0 | 0.0 | 0.0 | 0.0 | 2600.0 | 0.0 | 3400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 258 | 118 | 402 | 255 | 455 | -651.0 | 196 | 63 | 96 | 308 | -324.0 | 101 | -12.0 | -68.0 | 187 | 145 | 109 | 175 | -14.0 | 129 | 59 | 55 | 90 | -223.0 | -45.0 | 47 | 69 | -27.0 | 142 | 26 | 75 | 68 | -39.0 | 66 | 15 | 72 | -33.0 | 103 | 76 | -141.0 | 11 | 40 | 56 | 108 | -95.0 | 36 |
| Percentage of GainLossOnInvestments | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 25500.0 | 45500.0 | -65100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 12900.0 | 5900.0 | 0.0 | 0.0 | -11150.0 | -4500.0 | 4700.0 | 0.0 | 0.0 | 0.0 | 2600.0 | 0.0 | 3400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 101.6 | 40.0 | 0.0 | 77.0 | 167.9 | -197.3 | 0.0 | 22.9 | 38.1 | 97.2 | 0.0 | 32.8 | -4.4 | -17.1 | 0.0 | 49.0 | 40.7 | 53.0 | 0.0 | 25.7 | 16.5 | 20.5 | 0.0 | -108.3 | -29.4 | 22.3 | 0.0 | -24.1 | 70.6 | 7.8 | 0.0 | 17.7 | -11.1 | 16.8 | 0.0 | 15.2 | -7.9 | 27.8 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 551 | -282.0 | 668 | 786 | 794 | 85 | 957 | 1102 | 644 | 1282 | -31.0 | 947 | 613 | 702 | 1225 | 1326 | 1.0 | 1206 | 392 | 871 | 415 | 310 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 78600.0 | 79400.0 | 8500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 87100.0 | 41500.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 36 | 14 | 4.0 | 68 | -15.0 | 14 | 10.0 | 65 | 14 | 10.0 | -1.0 | 69 | 10.0 | 8.0 | 14 | 65 | 12 | 12 | 12 | 70 | 5.0 | -133.0 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 6.5 | -5.0 | 0.6 | 8.7 | -1.9 | 16.5 | 1.0 | 5.9 | 2.2 | 0.8 | 3.2 | 7.3 | 1.6 | 1.1 | 1.1 | 4.9 | 1200.0 | 1.0 | 3.1 | 8.0 | 1.2 | -42.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | -1500.0 | 1400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 7000.0 | 500.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 3600.0 | 1400.0 | 0.0 | 6800.0 | -1500.0 | 1400.0 | 0.0 | 6500.0 | 1400.0 | 1000.0 | 0.0 | 6900.0 | 1000.0 | 800.0 | 0.0 | 0.0 | 1200.0 | 1200.0 | 0.0 | 7000.0 | 500.0 | -13300.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 37 | 196 | 91 | 61 | 17 | 222 | 119 | 67 | 56 | 196 | 86 | 81 | 64 | 156 | 143 | 102 | 76 | 205 | 168 | 92 | 40 | 167 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 6.7 | -69.5 | 13.6 | 7.8 | 2.1 | 261.2 | 12.4 | 6.1 | 8.7 | 15.3 | -277.4 | 8.6 | 10.4 | 22.2 | 11.7 | 7.7 | 7600.0 | 17.0 | 42.9 | 10.6 | 9.6 | 53.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6100.0 | 1700.0 | 22200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 9200.0 | 4000.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 528.6 | 3266.7 | 0.0 | 1016.7 | 425.0 | 3700.0 | 0.0 | 1116.7 | 933.3 | 3266.7 | 0.0 | 1350.0 | 1066.7 | 2600.0 | 0.0 | 3400.0 | 2533.3 | 4100.0 | 0.0 | 1314.3 | 1000.0 | 3340.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 238 | 236 | 169 | 256 | -15.0 | 204 | 177 | 245 | 232 | 197 | 169 | 245 | 207 | 211 | 209 | 320 | 222 | 233 | 138 | 112 | 236 | 192 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 43.2 | -83.7 | 25.3 | 32.6 | -1.9 | 240.0 | 18.5 | 22.2 | 36.0 | 15.4 | -545.2 | 25.9 | 33.8 | 30.1 | 17.1 | 24.1 | 22200.0 | 19.3 | 35.2 | 12.9 | 56.9 | 61.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 25600.0 | -1500.0 | 20400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 11200.0 | 23600.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 4760.0 | 3933.3 | 0.0 | 1706.7 | -136.4 | 4080.0 | 0.0 | 6125.0 | 4640.0 | 4925.0 | 0.0 | 6125.0 | 4140.0 | 1507.1 | 0.0 | 10666.7 | 7400.0 | 4660.0 | 0.0 | 2800.0 | 7866.7 | 3840.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 31 | 61 | 29 | 28 | -9.0 | 52 | 37 | 38 | 34 | 60 | 35 | 38 | 31 | 38 | 42 | 50 | 31 | 68 | 11 | 63 | 20 | -81.0 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 5.6 | -21.6 | 4.3 | 3.6 | -1.1 | 61.2 | 3.9 | 3.4 | 5.3 | 4.7 | -112.9 | 4.0 | 5.1 | 5.4 | 3.4 | 3.8 | 3100.0 | 5.6 | 2.8 | 7.2 | 4.8 | -26.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 2800.0 | -900.0 | 5200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 6300.0 | 2000.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 1550.0 | 3050.0 | 0.0 | 933.3 | -450.0 | 2600.0 | 0.0 | 3800.0 | 1700.0 | 3000.0 | 0.0 | 1900.0 | 1550.0 | 1900.0 | 0.0 | 2500.0 | 1550.0 | 3400.0 | 0.0 | 3150.0 | 1000.0 | -4050.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 124 | -947.0 | 304 | 219 | 860 | -547.0 | 562 | 501 | 202 | 652 | -435.0 | 389 | 209 | 202 | 703 | 596 | -415.0 | 546 | 8.0 | 450 | 5.0 | 411 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 22.5 | 335.8 | 45.5 | 27.9 | 108.3 | -643.5 | 58.7 | 45.5 | 31.4 | 50.9 | 1403.2 | 41.1 | 34.1 | 28.8 | 57.4 | 44.9 | -41500.0 | 45.3 | 2.0 | 51.7 | 1.2 | 132.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 21900.0 | 86000.0 | -54700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 45000.0 | 500.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 48.8 | -321.0 | 0.0 | 66.2 | 317.3 | -165.8 | 0.0 | 182.2 | 80.2 | 205.7 | 0.0 | 126.3 | 76.6 | 50.8 | 0.0 | 201.4 | -154.9 | 165.5 | 0.0 | 89.6 | 1.4 | 153.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 106 | 177 | 107 | 122 | 32 | 155 | 132 | 154 | 115 | 193 | 135 | 124 | 95 | 111 | 127 | 140 | 108 | 163 | 120 | 176 | 123 | 167 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 19.2 | -62.8 | 16.0 | 15.5 | 4.0 | 182.4 | 13.8 | 14.0 | 17.9 | 15.1 | -435.5 | 13.1 | 15.5 | 15.8 | 10.4 | 10.6 | 10800.0 | 13.5 | 30.6 | 20.2 | 29.6 | 53.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 12200.0 | 3200.0 | 15500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 17600.0 | 12300.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 5300.0 | 8850.0 | 0.0 | 4066.7 | 1600.0 | 7750.0 | 0.0 | 15400.0 | 5750.0 | 19300.0 | 0.0 | 6200.0 | 4750.0 | 5550.0 | 0.0 | 7000.0 | 5400.0 | 16300.0 | 0.0 | 8800.0 | 6150.0 | 16700.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 138 | 136 | 78 | 215 | 7.0 | 119 | 78 | 203 | 112 | 122 | 69 | 191 | 99 | 74 | 110 | 236 | 102 | 131 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 25.0 | -48.2 | 11.7 | 27.4 | 0.9 | 140.0 | 8.2 | 18.4 | 17.4 | 9.5 | -222.6 | 20.2 | 16.2 | 10.5 | 9.0 | 17.8 | 10200.0 | 10.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 21500.0 | 700.0 | 11900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 3450.0 | 4533.3 | 0.0 | 3583.3 | 233.3 | 3966.7 | 0.0 | 5075.0 | 3733.3 | 4066.7 | 0.0 | 6366.7 | 3300.0 | 1850.0 | 0.0 | 1966.7 | 850.0 | 1091.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 72 | 65 | 48 | 121 | 33 | 57 | 33 | 103 | 66 | 57 | 42 | 87 | 61 | 33 | 65 | 125 | 63 | 58 | 29 | 114 | 72 | -133.0 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 13.1 | -23.0 | 7.2 | 15.4 | 4.2 | 67.1 | 3.4 | 9.3 | 10.2 | 4.4 | -135.5 | 9.2 | 10.0 | 4.7 | 5.3 | 9.4 | 6300.0 | 4.8 | 7.4 | 13.1 | 17.3 | -42.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 12100.0 | 3300.0 | 5700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 11400.0 | 7200.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 7200.0 | 6500.0 | 0.0 | 4033.3 | 3300.0 | 5700.0 | 0.0 | 5150.0 | 6600.0 | 2850.0 | 0.0 | 4350.0 | 3050.0 | 1650.0 | 0.0 | 12500.0 | 6300.0 | 5800.0 | 0.0 | 11400.0 | 7200.0 | -13300.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | -1.0 | -4.0 | -3.0 | -2.0 | -2.0 | 106 | 65 | 192 | 106 | 113 | 62 | 179 | 85 | 64 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | -0.2 | 1.4 | -0.4 | -0.3 | -0.3 | 124.7 | 6.8 | 17.4 | 16.5 | 8.8 | -200.0 | 18.9 | 13.9 | 9.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -200.0 | -200.0 | 10600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC us-gaap:CorporateNonSegment us-gaap:CorporateAndOther | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | -92.0 | -80.0 | -81.0 | -87.0 | -108.0 | -69.0 | -109.0 | -68.0 | -73.0 | -78.0 | -54.0 | -83.0 | -61.0 | -52.0 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | -16.7 | 28.4 | -12.1 | -11.1 | -13.6 | -81.2 | -11.4 | -6.2 | -11.3 | -6.1 | 174.2 | -8.8 | -10.0 | -7.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -8700.0 | -10800.0 | -6900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:CorporateNonSegment us-gaap:CorporateAndOther | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 36 | 14 | 4.0 | 68 | -15.0 | 14 | 10.0 | 65 | 14 | 10.0 | -1.0 | 69 | 10.0 | 8.0 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 6.5 | -5.0 | 0.6 | 8.7 | -1.9 | 16.5 | 1.0 | 5.9 | 2.2 | 0.8 | 3.2 | 7.3 | 1.6 | 1.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | -1500.0 | 1400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:AtlanticCityElectricCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 37 | 196 | 91 | 61 | 17 | 222 | 119 | 67 | 56 | 196 | 86 | 81 | 64 | 156 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 6.7 | -69.5 | 13.6 | 7.8 | 2.1 | 261.2 | 12.4 | 6.1 | 8.7 | 15.3 | -277.4 | 8.6 | 10.4 | 22.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6100.0 | 1700.0 | 22200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:BaltimoreGasAndElectricCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 238 | 236 | 169 | 256 | -15.0 | 204 | 177 | 245 | 232 | 197 | 169 | 245 | 207 | 211 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 43.2 | -83.7 | 25.3 | 32.6 | -1.9 | 240.0 | 18.5 | 22.2 | 36.0 | 15.4 | -545.2 | 25.9 | 33.8 | 30.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 25600.0 | -1500.0 | 20400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:CommonwealthEdisonCo | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 31 | 61 | 29 | 28 | -9.0 | 52 | 37 | 38 | 34 | 60 | 35 | 38 | 31 | 38 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 5.6 | -21.6 | 4.3 | 3.6 | -1.1 | 61.2 | 3.9 | 3.4 | 5.3 | 4.7 | -112.9 | 4.0 | 5.1 | 5.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 2800.0 | -900.0 | 5200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:DelmarvaPowerandLightCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 124 | -947.0 | 304 | 219 | 860 | -547.0 | 562 | 501 | 202 | 652 | -435.0 | 389 | 209 | 202 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 22.5 | 335.8 | 45.5 | 27.9 | 108.3 | -643.5 | 58.7 | 45.5 | 31.4 | 50.9 | 1403.2 | 41.1 | 34.1 | 28.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 21900.0 | 86000.0 | -54700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ExelonGenerationCoLLC | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 106 | 177 | 107 | 122 | 32 | 155 | 132 | 154 | 115 | 193 | 135 | 124 | 95 | 111 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 19.2 | -62.8 | 16.0 | 15.5 | 4.0 | 182.4 | 13.8 | 14.0 | 17.9 | 15.1 | -435.5 | 13.1 | 15.5 | 15.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 12200.0 | 3200.0 | 15500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PecoEnergyCo | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 138 | 136 | 78 | 215 | 7.0 | 119 | 78 | 203 | 112 | 122 | 69 | 191 | 99 | 74 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 25.0 | -48.2 | 11.7 | 27.4 | 0.9 | 140.0 | 8.2 | 18.4 | 17.4 | 9.5 | -222.6 | 20.2 | 16.2 | 10.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 21500.0 | 700.0 | 11900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PepcoHoldingsLLC | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 72 | 65 | 48 | 121 | 33 | 57 | 33 | 103 | 66 | 57 | 42 | 87 | 61 | 33 |
| Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | 13.1 | -23.0 | 7.2 | 15.4 | 4.2 | 67.1 | 3.4 | 9.3 | 10.2 | 4.4 | -135.5 | 9.2 | 10.0 | 4.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 12100.0 | 3300.0 | 5700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PotomacElectricPowerCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 74 | -19.0 | 232 | 216 | 219 | -294.0 | 148 | 172 | 144 | 310 | 26 | 137 | 66 | 59 | -720.0 | 452 | -72.0 | 215 | 136 | 340 | 102 | 184 | 268 | 115 | 327 | 363 | 20 | 422 | 277 | -54.0 | 311 | 439 | 239 | 56 | 182 | 161 | 126 | 158 | 423 | 255 | 332 | 446 | 367 | 552 | 176 | 563 |
| Percentage of IncomeTaxExpenseBenefit | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 21600.0 | 21900.0 | -29400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 34000.0 | 10200.0 | 0.0 | 0.0 | 5750.0 | 32700.0 | 36300.0 | 0.0 | 0.0 | 0.0 | -5400.0 | 0.0 | 21950.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 380 | 388 | 398 | 421 | 404 | 389 | 403 | 403 | 397 | 410 | 387 | 367 | 365 | 359 | 377 | 426 | 363 | 347 | 506 | 366 | 277 | 268 | 243 | 145 | 335 | 333 | 247 | 228 | 217 | 224 | 228 | 246 | 617 | 225 | 240 | 250 | 189 | 175 | 176 | 176 | 175 | 177 | 169 | 269 | 177 |
| Percentage of InterestExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 39800.0 | 42100.0 | 40400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 50600.0 | 36600.0 | 0.0 | 0.0 | 12150.0 | 14500.0 | 33500.0 | 0.0 | 0.0 | 0.0 | 21700.0 | 0.0 | 11400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 15 | 14 | 15 | 15 | 14 | 14 | 15 | 15 | 14 | 16 | 16 | 16 | 16 | 15 | 15 | 15 | 15 | 15 | 15 | 16 | 16 | 16 | 16 | 16 | 16 |
| Percentage of InterestExpense | 3.9 | 3.6 | 3.8 | 3.6 | 3.5 | 3.6 | 3.7 | 3.7 | 3.5 | 3.9 | 4.1 | 4.4 | 4.4 | 4.2 | 4.0 | 3.5 | 4.1 | 4.3 | 3.0 | 4.4 | 5.8 | 6.0 | 6.6 | 11.0 | 4.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 1500.0 | 1500.0 | 1400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 1500.0 | 1600.0 | 0.0 | 0.0 | 800.0 | 1600.0 | 1600.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 1500.0 | 0.0 | 1500.0 | 1500.0 | 1400.0 | 0.0 | 1500.0 | 1500.0 | 1400.0 | 0.0 | 1600.0 | 1600.0 | 1600.0 | 0.0 | 0.0 | 1500.0 | 1500.0 | 0.0 | 1500.0 | 1600.0 | 1600.0 | 0.0 | 1600.0 | 1600.0 | 1600.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | 34 | 34 | 34 | 32 | 32 | 32 | 31 | 29 | 29 | 28 | 27 | 25 | 25 | 26 | 24 | 22 | 23 | 23 | 24 | 20 | 20 | 21 | 21 | 20 | 21 | 21 | 22 | 23 | 23 | 12 | 29 | 32 | 33 | 34 | 35 | 34 | 41 | 32 | 32 | 32 | 33 |
| Percentage of InterestExpense | 8.9 | 8.8 | 8.5 | 7.6 | 7.9 | 8.2 | 7.7 | 7.2 | 7.3 | 6.8 | 7.0 | 6.8 | 6.8 | 7.2 | 6.4 | 5.2 | 6.3 | 6.6 | 4.7 | 5.5 | 7.2 | 7.8 | 8.6 | 13.8 | 6.3 | 6.3 | 8.9 | 10.1 | 10.6 | 5.4 | 12.7 | 13.0 | 5.3 | 15.1 | 14.6 | 13.6 | 21.7 | 18.3 | 18.2 | 18.2 | 18.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 3400.0 | 3200.0 | 3200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 2400.0 | 2000.0 | 0.0 | 0.0 | 1050.0 | 2000.0 | 2100.0 | 0.0 | 0.0 | 0.0 | 2300.0 | 0.0 | 1450.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 566.7 | 0.0 | 566.7 | 800.0 | 533.3 | 0.0 | 516.7 | 483.3 | 483.3 | 0.0 | 450.0 | 416.7 | 416.7 | 0.0 | 800.0 | 733.3 | 460.0 | 0.0 | 342.9 | 500.0 | 400.0 | 0.0 | 700.0 | 2000.0 | 300.0 | 0.0 | 733.3 | 1150.0 | 143.8 | 0.0 | 1450.0 | 800.0 | 825.0 | 0.0 | 875.0 | 1700.0 | 1366.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 93 | 92 | 92 | 95 | 91 | 88 | 87 | 86 | 84 | 83 | 82 | 82 | 86 | 83 | 86 | 98 | 82 | 84 | 194 | 88 | 83 | 81 | 80 | 78 | 81 | 77 | 78 | 76 | 77 | 73 | 71 | 72 | 350 | 73 | 71 | 71 | 79 | 84 | 82 | 82 | 82 | 83 | 79 | 130 | 81 |
| Percentage of InterestExpense | 24.5 | 23.7 | 23.1 | 22.6 | 22.5 | 22.6 | 21.6 | 21.3 | 21.2 | 20.2 | 21.2 | 22.3 | 23.6 | 23.1 | 22.8 | 23.0 | 22.6 | 24.2 | 38.3 | 24.0 | 30.0 | 30.2 | 32.9 | 53.8 | 24.2 | 23.1 | 31.6 | 33.3 | 35.5 | 32.6 | 31.1 | 29.3 | 56.7 | 32.4 | 29.6 | 28.4 | 41.8 | 48.0 | 46.6 | 46.6 | 46.9 | 46.9 | 46.7 | 48.3 | 45.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 9200.0 | 9500.0 | 9100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 19400.0 | 8800.0 | 0.0 | 0.0 | 4000.0 | 7800.0 | 8100.0 | 0.0 | 0.0 | 0.0 | 7700.0 | 0.0 | 3550.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 1550.0 | 0.0 | 613.3 | 863.6 | 1820.0 | 0.0 | 2175.0 | 1720.0 | 2100.0 | 0.0 | 2050.0 | 1640.0 | 614.3 | 0.0 | 2866.7 | 3266.7 | 1640.0 | 0.0 | 4850.0 | 2933.3 | 1660.0 | 0.0 | 8000.0 | 7800.0 | 8100.0 | 0.0 | 7800.0 | 0.0 | 7700.0 | 0.0 | 7100.0 | 0.0 | 35000.0 | 0.0 | 0.0 | 7100.0 | 7900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 15 | 14 | 15 | 15 | 16 | 16 | 15 | 15 | 15 | 16 | 15 | 14 | 13 | 13 | 13 | 13 | 13 | 13 | 12 | 13 | 12 | 13 | 12 | 13 | 12 |
| Percentage of InterestExpense | 3.9 | 3.6 | 3.8 | 3.6 | 4.0 | 4.1 | 3.7 | 3.7 | 3.8 | 3.9 | 3.9 | 3.8 | 3.6 | 3.6 | 3.4 | 3.1 | 3.6 | 3.7 | 2.4 | 3.6 | 4.3 | 4.9 | 4.9 | 9.0 | 3.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 1500.0 | 1500.0 | 1600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 1200.0 | 1300.0 | 0.0 | 0.0 | 600.0 | 1300.0 | 1200.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 750.0 | 0.0 | 500.0 | 750.0 | 800.0 | 0.0 | 1500.0 | 750.0 | 750.0 | 0.0 | 750.0 | 700.0 | 650.0 | 0.0 | 650.0 | 650.0 | 650.0 | 0.0 | 600.0 | 650.0 | 600.0 | 0.0 | 1200.0 | 650.0 | 600.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 68 | 77 | 72 | 78 | 100 | 84 | 101 | 107 | 102 | 118 | 93 | 93 | 91 | 88 | 103 | 120 | 90 | 82 | 67 | 89 | 87 | 86 | 56 | 90 | 90 | 79 | 77 | 74 | 73 | 41 | 82 | 93 | 82 | 78 | 85 | 85 | 54 | 42 | 37 | 45 | 45 | 44 | 37 | 37 | 35 |
| Percentage of InterestExpense | 17.9 | 19.8 | 18.1 | 18.5 | 24.8 | 21.6 | 25.1 | 26.6 | 25.7 | 28.8 | 24.0 | 25.3 | 24.9 | 24.5 | 27.3 | 28.2 | 24.8 | 23.6 | 13.2 | 24.3 | 31.4 | 32.1 | 23.0 | 62.1 | 26.9 | 23.7 | 31.2 | 32.5 | 33.6 | 18.3 | 36.0 | 37.8 | 13.3 | 34.7 | 35.4 | 34.0 | 28.6 | 24.0 | 21.0 | 25.6 | 25.7 | 24.9 | 21.9 | 13.8 | 19.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 7200.0 | 7800.0 | 10000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 6700.0 | 8900.0 | 0.0 | 0.0 | 2800.0 | 9000.0 | 9000.0 | 0.0 | 0.0 | 0.0 | 7300.0 | 0.0 | 4100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 23.1 | 0.0 | 21.8 | 28.8 | 30.3 | 0.0 | 36.7 | 42.5 | 32.2 | 0.0 | 30.2 | 34.1 | 22.9 | 0.0 | 34.8 | 44.8 | 27.3 | 0.0 | 13.3 | 24.9 | 32.5 | 0.0 | 27.2 | 58.8 | 42.7 | 0.0 | 68.8 | 36.8 | 21.9 | 0.0 | 21.4 | 26.4 | 20.9 | 0.0 | 18.0 | 20.2 | 14.6 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 35 | 36 | 36 | 33 | 33 | 33 | 30 | 30 | 30 | 30 | 28 | 28 | 30 | 31 | 28 | 28 | 28 | 28 | 27 | 28 | 28 | 27 | 25 | 25 | 25 | 25 | 26 | 25 | 25 | 26 | 26 | 25 | 26 | 26 | 29 | 28 | 28 | 29 | 31 | 31 | 31 | 30 | 35 | 74 | 42 |
| Percentage of InterestExpense | 9.2 | 9.3 | 9.0 | 7.8 | 8.2 | 8.5 | 7.4 | 7.4 | 7.6 | 7.3 | 7.2 | 7.6 | 8.2 | 8.6 | 7.4 | 6.6 | 7.7 | 8.1 | 5.3 | 7.7 | 10.1 | 10.1 | 10.3 | 17.2 | 7.5 | 7.5 | 10.5 | 11.0 | 11.5 | 11.6 | 11.4 | 10.2 | 4.2 | 11.6 | 12.1 | 11.2 | 14.8 | 16.6 | 17.6 | 17.6 | 17.7 | 16.9 | 20.7 | 27.5 | 23.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 3600.0 | 3300.0 | 3300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 2700.0 | 2800.0 | 0.0 | 0.0 | 1250.0 | 2500.0 | 2500.0 | 0.0 | 0.0 | 0.0 | 2500.0 | 0.0 | 1300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 1750.0 | 0.0 | 1200.0 | 1650.0 | 1650.0 | 0.0 | 3000.0 | 1500.0 | 3000.0 | 0.0 | 1400.0 | 1400.0 | 1500.0 | 0.0 | 1400.0 | 1400.0 | 2800.0 | 0.0 | 1350.0 | 1400.0 | 2800.0 | 0.0 | 2500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 2500.0 | 0.0 | 2600.0 | 0.0 | 0.0 | 0.0 | 2900.0 | 2800.0 | 2800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 67 | 67 | 67 | 67 | 67 | 66 | 66 | 67 | 65 | 68 | 65 | 65 | 63 | 62 | 62 | 59 | 62 |
| Percentage of InterestExpense | 17.6 | 17.3 | 16.8 | 15.9 | 16.6 | 17.0 | 16.4 | 16.6 | 16.4 | 16.6 | 16.8 | 17.7 | 17.3 | 17.3 | 16.4 | 13.8 | 17.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 6700.0 | 6700.0 | 6700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 2233.3 | 0.0 | 1116.7 | 2233.3 | 2233.3 | 0.0 | 1650.0 | 2233.3 | 2166.7 | 0.0 | 2166.7 | 2166.7 | 1575.0 | 0.0 | 516.7 | 491.7 | 516.7 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 34 | 35 | 35 | 34 | 34 | 33 | 33 | 34 | 34 | 32 | 32 | 32 | 31 | 32 | 31 | 28 | 29 | 29 | 30 | 31 | 37 | 32 | 31 | 31 | 30 |
| Percentage of InterestExpense | 8.9 | 9.0 | 8.8 | 8.1 | 8.4 | 8.5 | 8.2 | 8.4 | 8.6 | 7.8 | 8.3 | 8.7 | 8.5 | 8.9 | 8.2 | 6.6 | 8.0 | 8.4 | 5.9 | 8.5 | 13.4 | 11.9 | 12.8 | 21.4 | 9.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 3500.0 | 3400.0 | 3400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 3000.0 | 3100.0 | 0.0 | 0.0 | 1550.0 | 3100.0 | 3000.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 3400.0 | 0.0 | 1166.7 | 3400.0 | 3400.0 | 0.0 | 1650.0 | 3400.0 | 1700.0 | 0.0 | 1600.0 | 1600.0 | 1550.0 | 0.0 | 3100.0 | 2800.0 | 2900.0 | 0.0 | 3000.0 | 3100.0 | 3700.0 | 0.0 | 3100.0 | 3100.0 | 3000.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | -61.0 | -793.0 | 19 | 49 | 476 | 45 | 397 | 257 | 108 | 363 | -178.0 | 234 | 178 | 136 | 2224 | 305 | -250.0 | 423 | -42.0 | 236 | -8.0 | 310 | 137 | 87 | 165 | 166 | 446 | 386 | 443 | 495 | 424 | 605 | 382 | 561 | 425 | 657 | 512 | 528 |
| Percentage of NetIncomeLoss | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 4900.0 | 47600.0 | 4500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 23600.0 | -800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | -24.0 | -268.8 | 0.0 | 14.8 | 175.6 | 13.6 | 0.0 | 93.5 | 42.9 | 114.5 | 0.0 | 76.0 | 65.2 | 34.2 | 0.0 | 103.0 | -93.3 | 128.2 | 0.0 | 47.0 | -2.2 | 115.7 | 0.0 | 18.4 | 39.3 | 44.9 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-09-30 | 2017-06-30 |
| Value | 75 | 25 | 76 | 68 | 53 | -206.0 | 36 | -12.0 | 10.0 | 59 | -47.0 | 67 | 3.0 | 51 | 42 | -1.0 |
| Percentage of NetIncomeLossAttributableToNoncontrollingInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | 5300.0 | -20600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 |
| Value | 74 | 24 | 75 | 68 | 53 | -206.0 | 36 | -13.0 | 10.0 | 59 | -47.0 | 66 | 3.0 | 50 | 56 | 42 | -1.0 |
| Percentage of NetIncomeLossAttributableToNoncontrollingInterest | 98.7 | 96.0 | 98.7 | 100.0 | 100.0 | 100.0 | 100.0 | 108.3 | 100.0 | 100.0 | 100.0 | 98.5 | 100.0 | 98.0 | 0.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | 5300.0 | -20600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 29.1 | 8.1 | 0.0 | 20.5 | 19.6 | -62.4 | 0.0 | -4.7 | 4.0 | 18.6 | 0.0 | 21.4 | 1.1 | 12.6 | 0.0 | 14.2 | -0.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | 401 | -289.0 | 359 | 501 | 521 | 582 | 773 | 772 | 484 | 907 | 152 | 733 | 539 | 585 | 1871 | 824 | 80 | 995 | 204 | 490 | 267 | 173 | 309 | 629 | 638 | 693 | 19 | 993 | 522 | 90 | 495 | 738 | 490 | -4.0 | 378 | 296 | 286 | 200 | 606 | 601 | 620 | 668 |
| Percentage of NetIncomeLossAvailableToCommonStockholdersBasic | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 50100.0 | 52100.0 | 58200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 49000.0 | 26700.0 | 0.0 | 0.0 | 31450.0 | 63800.0 | 69300.0 | 0.0 | 0.0 | 0.0 | 9000.0 | 0.0 | 36900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 185 | -161.0 | 399 | 17 | 229 | -1135.0 | -5.0 | -251.0 | -197.0 | 64 | -740.0 | -199.0 | -329.0 | -399.0 | -35.0 | -149.0 | -231.0 | -90.0 | -321.0 | -396.0 | -232.0 | -173.0 | -145.0 | -497.0 | -172.0 | -265.0 | -590.0 | 96 | 5.0 | -124.0 | -84.0 | -79.0 | -269.0 | -451.0 | -138.0 | -145.0 | -299.0 | -1.0 | -34.0 | -325.0 | -82.0 | -88.0 | -49.0 | 31 | -397.0 | -90.0 |
| Percentage of NonoperatingIncomeExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 1700.0 | 22900.0 | -113500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -39600.0 | -23200.0 | 0.0 | 0.0 | -24850.0 | -17200.0 | -26500.0 | 0.0 | 0.0 | 0.0 | -12400.0 | 0.0 | -3950.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | -14.0 | -14.0 | -13.0 | -14.0 | -13.0 | -13.0 | -13.0 | -14.0 | -14.0 | -11.0 | -16.0 | -15.0 | -15.0 | -15.0 | -14.0 | -14.0 | -13.0 | -13.0 | -14.0 | -13.0 | -14.0 | -12.0 | -17.0 | -15.0 | -15.0 | -15.0 |
| Percentage of NonoperatingIncomeExpense | -7.6 | 8.7 | -3.3 | -82.4 | -5.7 | 1.1 | 260.0 | 5.6 | 7.1 | -17.2 | 2.2 | 7.5 | 4.6 | 3.8 | 40.0 | 9.4 | 5.6 | 14.4 | 4.4 | 3.3 | 6.0 | 6.9 | 11.7 | 3.0 | 8.7 | 5.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -1400.0 | -1300.0 | -1300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -1300.0 | -1400.0 | 0.0 | 0.0 | -750.0 | -1500.0 | -1500.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | -1400.0 | -1400.0 | 0.0 | -1400.0 | -1300.0 | -1300.0 | 0.0 | -1400.0 | -1400.0 | -1100.0 | 0.0 | -1500.0 | -1500.0 | -1500.0 | 0.0 | 0.0 | -1300.0 | -1300.0 | 0.0 | -1300.0 | -1400.0 | -1200.0 | 0.0 | -1500.0 | -1500.0 | -1500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | -25.0 | -26.0 | -28.0 | -28.0 | -26.0 | -27.0 | -22.0 | -24.0 | -24.0 | -24.0 | -23.0 | -22.0 | -21.0 | -21.0 | -21.0 | -22.0 | -22.0 | -23.0 | -22.0 | -23.0 | -19.0 | -20.0 | -21.0 | -21.0 | -20.0 | -21.0 | -21.0 | -22.0 | -22.0 | -23.0 | -24.0 | -25.0 | -28.0 | -28.0 | -29.0 | -30.0 | -27.0 | -35.0 | -28.0 | -24.0 | -26.0 | -25.0 |
| Percentage of NonoperatingIncomeExpense | -13.5 | 16.1 | -7.0 | -164.7 | -11.4 | 2.4 | 440.0 | 9.6 | 12.2 | -37.5 | 3.1 | 11.1 | 6.4 | 5.3 | 60.0 | 14.8 | 9.5 | 25.6 | 6.9 | 5.8 | 8.2 | 11.6 | 14.5 | 4.2 | 11.6 | 7.9 | 3.6 | -22.9 | -440.0 | 18.5 | 28.6 | 31.6 | 10.4 | 6.2 | 21.0 | 20.7 | 9.0 | 3500.0 | 82.4 | 7.4 | 31.7 | 28.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -2800.0 | -2600.0 | -2700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -2300.0 | -1900.0 | 0.0 | 0.0 | -1050.0 | -2000.0 | -2100.0 | 0.0 | 0.0 | 0.0 | -2300.0 | 0.0 | -1250.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | -357.1 | -433.3 | 0.0 | -466.7 | -650.0 | -450.0 | 0.0 | -400.0 | -400.0 | -400.0 | 0.0 | -366.7 | -350.0 | -350.0 | 0.0 | -733.3 | -733.3 | -460.0 | 0.0 | -328.6 | -475.0 | -400.0 | 0.0 | -700.0 | -2000.0 | -300.0 | 0.0 | -733.3 | -1100.0 | -143.8 | 0.0 | -1250.0 | -700.0 | -700.0 | 0.0 | -750.0 | -1350.0 | -1166.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | -83.0 | -89.0 | -84.0 | -85.0 | -87.0 | -84.0 | -79.0 | -83.0 | -79.0 | -79.0 | -74.0 | -78.0 | -81.0 | -81.0 | -78.0 | -84.0 | -97.0 | -81.0 | -80.0 | -277.0 | -88.0 | -82.0 | -77.0 | -79.0 | -76.0 | -81.0 | -77.0 | -77.0 | -75.0 | -75.0 | -68.0 | -67.0 | -70.0 | -348.0 | -50.0 | -69.0 | -71.0 | -78.0 | -83.0 | -70.0 | -82.0 | -81.0 | -76.0 | -79.0 | -126.0 | -81.0 |
| Percentage of NonoperatingIncomeExpense | -44.9 | 55.3 | -21.1 | -500.0 | -38.0 | 7.4 | 1580.0 | 33.1 | 40.1 | -123.4 | 10.0 | 39.2 | 24.6 | 20.3 | 222.9 | 56.4 | 42.0 | 90.0 | 24.9 | 69.9 | 37.9 | 47.4 | 53.1 | 15.9 | 44.2 | 30.6 | 13.1 | -80.2 | -1500.0 | 60.5 | 81.0 | 84.8 | 26.0 | 77.2 | 36.2 | 47.6 | 23.7 | 7800.0 | 244.1 | 21.5 | 100.0 | 92.0 | 155.1 | -254.8 | 31.7 | 90.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -8500.0 | -8700.0 | -8400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -27700.0 | -8800.0 | 0.0 | 0.0 | -3950.0 | -7600.0 | -8100.0 | 0.0 | 0.0 | 0.0 | -7500.0 | 0.0 | -3350.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | -1660.0 | -1483.3 | 0.0 | -566.7 | -790.9 | -1680.0 | 0.0 | -2075.0 | -1580.0 | -1975.0 | 0.0 | -1950.0 | -1620.0 | -578.6 | 0.0 | -2800.0 | -3233.3 | -1620.0 | 0.0 | -6925.0 | -2933.3 | -1640.0 | 0.0 | -7900.0 | -7600.0 | -8100.0 | 0.0 | -7700.0 | 0.0 | -7500.0 | 0.0 | -6700.0 | 0.0 | -34800.0 | 0.0 | 0.0 | -7100.0 | -7800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | -12.0 | -12.0 | -11.0 | -13.0 | -13.0 | -14.0 | -13.0 | -13.0 | -10.0 | -12.0 | -13.0 | -13.0 | -11.0 | -11.0 | -9.0 | -9.0 | -10.0 | -10.0 | -9.0 | -9.0 | -10.0 | -9.0 | -11.0 | -8.0 | -11.0 | -10.0 |
| Percentage of NonoperatingIncomeExpense | -6.5 | 7.5 | -2.8 | -76.5 | -5.7 | 1.2 | 260.0 | 5.2 | 5.1 | -18.8 | 1.8 | 6.5 | 3.3 | 2.8 | 25.7 | 6.0 | 4.3 | 11.1 | 2.8 | 2.3 | 4.3 | 5.2 | 7.6 | 1.6 | 6.4 | 3.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -1300.0 | -1300.0 | -1400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -900.0 | -1000.0 | 0.0 | 0.0 | -400.0 | -1100.0 | -1000.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | -600.0 | -600.0 | 0.0 | -433.3 | -650.0 | -700.0 | 0.0 | -1300.0 | -500.0 | -600.0 | 0.0 | -650.0 | -550.0 | -550.0 | 0.0 | -450.0 | -500.0 | -500.0 | 0.0 | -450.0 | -500.0 | -450.0 | 0.0 | -800.0 | -550.0 | -500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 432 | 95 | 658 | 287 | 515 | -880.0 | 201 | 19 | 55 | 319 | -469.0 | 78 | -73.0 | -145.0 | 202 | 96 | 52 | 159 | -85.0 | 108 | 18 | -4.0 | 37 | -325.0 | -130.0 | -8.0 | -350.0 | 253 | 142 | 5.0 | 39 | 52 | -126.0 | 46 | -24.0 | -2.0 | -161.0 | 124 | 91 | -201.0 | 31 | 30 | 75 | 155 | -170.0 | 44 |
| Percentage of NonoperatingIncomeExpense | 233.5 | -59.0 | 164.9 | 1688.2 | 224.9 | 77.5 | -4020.0 | -7.6 | -27.9 | 498.4 | 63.4 | -39.2 | 22.2 | 36.3 | -577.1 | -64.4 | -22.5 | -176.7 | 26.5 | -27.3 | -7.8 | 2.3 | -25.5 | 65.4 | 75.6 | 3.0 | 59.3 | 263.5 | 2840.0 | -4.0 | -46.4 | -65.8 | 46.8 | -10.2 | 17.4 | 1.4 | 53.8 | -12400.0 | -267.6 | 61.8 | -37.8 | -34.1 | -153.1 | 500.0 | 42.8 | -48.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 28700.0 | 51500.0 | -88000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 10800.0 | 1800.0 | 0.0 | 0.0 | -16250.0 | -13000.0 | -800.0 | 0.0 | 0.0 | 0.0 | 500.0 | 0.0 | 2600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 170.1 | 32.2 | 0.0 | 86.7 | 190.0 | -266.7 | 0.0 | 6.9 | 21.8 | 100.6 | 0.0 | 25.3 | -26.7 | -36.4 | 0.0 | 32.4 | 19.4 | 48.2 | 0.0 | 21.5 | 5.0 | -1.5 | 0.0 | -157.8 | -85.0 | -3.8 | 0.0 | 225.9 | 70.6 | 1.5 | 0.0 | 13.5 | -35.8 | 11.7 | 0.0 | -0.4 | -38.3 | 33.5 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | -35.0 | -33.0 | -33.0 | -33.0 | -31.0 | -33.0 | -31.0 | -29.0 | -30.0 | -29.0 | -29.0 | -30.0 | -32.0 | -31.0 | -30.0 | -29.0 | -29.0 | -29.0 | -29.0 | -28.0 | -29.0 | -29.0 | -28.0 | -27.0 | -27.0 | -26.0 | -26.0 | -27.0 | -27.0 | -26.0 | -27.0 | -28.0 | -28.0 | -26.0 | -27.0 | -30.0 | -29.0 | -29.0 | -29.0 | -31.0 | -31.0 | -28.0 | -31.0 | -35.0 | -78.0 | -41.0 |
| Percentage of NonoperatingIncomeExpense | -18.9 | 20.5 | -8.3 | -194.1 | -13.5 | 2.9 | 620.0 | 11.6 | 15.2 | -45.3 | 3.9 | 15.1 | 9.7 | 7.8 | 85.7 | 19.5 | 12.6 | 32.2 | 9.0 | 7.1 | 12.5 | 16.8 | 19.3 | 5.4 | 15.7 | 9.8 | 4.4 | -28.1 | -540.0 | 21.0 | 32.1 | 35.4 | 10.4 | 5.8 | 19.6 | 20.7 | 9.7 | 2900.0 | 85.3 | 9.5 | 37.8 | 31.8 | 63.3 | -112.9 | 19.6 | 45.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -3300.0 | -3100.0 | -3300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -2800.0 | -2900.0 | 0.0 | 0.0 | -1350.0 | -2700.0 | -2600.0 | 0.0 | 0.0 | 0.0 | -2600.0 | 0.0 | -1400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | -1750.0 | -1650.0 | 0.0 | -1100.0 | -1550.0 | -1650.0 | 0.0 | -2900.0 | -1500.0 | -2900.0 | 0.0 | -1500.0 | -1600.0 | -1550.0 | 0.0 | -1450.0 | -1450.0 | -2900.0 | 0.0 | -1400.0 | -1450.0 | -2900.0 | 0.0 | -2700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -2600.0 | 0.0 | -2800.0 | 0.0 | 0.0 | 0.0 | -3000.0 | -2900.0 | -2900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | -47.0 | -50.0 | -52.0 | -51.0 | -53.0 | -54.0 | -50.0 | -53.0 | -53.0 | -53.0 | -58.0 | -54.0 | -54.0 | -52.0 | -48.0 | -49.0 | -46.0 | -49.0 |
| Percentage of NonoperatingIncomeExpense | -25.4 | 31.1 | -13.0 | -300.0 | -23.1 | 4.8 | 1000.0 | 21.1 | 26.9 | -82.8 | 7.8 | 27.1 | 16.4 | 13.0 | 137.1 | 32.9 | 19.9 | 54.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -5100.0 | -5300.0 | -5400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | -1175.0 | -1666.7 | 0.0 | -850.0 | -1766.7 | -1800.0 | 0.0 | -1325.0 | -1766.7 | -1766.7 | 0.0 | -1800.0 | -1800.0 | -1300.0 | 0.0 | -408.3 | -383.3 | -408.3 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | -22.0 | -22.0 | -25.0 | -25.0 | -25.0 | -25.0 | -24.0 | -24.0 | -27.0 | -27.0 | -24.0 | -25.0 | -24.0 | -23.0 | -22.0 | -24.0 | -21.0 | -21.0 | -21.0 | -18.0 | -25.0 | -28.0 | -25.0 | -23.0 | -23.0 | -25.0 |
| Percentage of NonoperatingIncomeExpense | -11.9 | 13.7 | -6.3 | -147.1 | -10.9 | 2.2 | 480.0 | 9.6 | 13.7 | -42.2 | 3.2 | 12.6 | 7.3 | 5.8 | 62.9 | 16.1 | 9.1 | 23.3 | 6.5 | 4.5 | 10.8 | 16.2 | 17.2 | 4.6 | 13.4 | 9.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -2500.0 | -2500.0 | -2500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -1800.0 | -2500.0 | 0.0 | 0.0 | -1150.0 | -2300.0 | -2500.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | -2200.0 | -2200.0 | 0.0 | -833.3 | -2500.0 | -2500.0 | 0.0 | -1200.0 | -2700.0 | -1350.0 | 0.0 | -1250.0 | -1200.0 | -1150.0 | 0.0 | -2400.0 | -2100.0 | -2100.0 | 0.0 | -1800.0 | -2500.0 | -2800.0 | 0.0 | -2300.0 | -2300.0 | -2500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 7561 | 10082 | 7853 | 8087 | 6769 | 7529 | 7393 | 7559 | 6881 | 8262 | 8107 | 8252 | 7138 | 8648 |
| Percentage of OperatingExpenses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 808700.0 | 676900.0 | 752900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | -95.0 | -96.0 | -94.0 | -91.0 | -98.0 | -90.0 | -98.0 | -94.0 | -101.0 | -105.0 | -111.0 | -104.0 | -112.0 | -112.0 |
| Percentage of OperatingExpenses | -1.3 | -1.0 | -1.2 | -1.1 | -1.4 | -1.2 | -1.3 | -1.2 | -1.5 | -1.3 | -1.4 | -1.3 | -1.6 | -1.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -9100.0 | -9800.0 | -9000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC us-gaap:IntersegmentElimination | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 96.8 | 0.0 | 101.1 | 102.0 | 99.1 | 0.0 | 99.0 | 102.8 | 99.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 97 | 97 | 94 | 94 | 97 | 93 | 101 | 95 | 100 | 108 | 113 | 105 | 110 | 114 |
| Percentage of OperatingExpenses | 1.3 | 1.0 | 1.2 | 1.2 | 1.4 | 1.2 | 1.4 | 1.3 | 1.5 | 1.3 | 1.4 | 1.3 | 1.5 | 1.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 9400.0 | 9700.0 | 9300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC us-gaap:CorporateNonSegment us-gaap:CorporateAndOther | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 |
| Value | -21.0 |
| Percentage of OperatingExpenses | -0.3 |
| Percentage of RevenueFromRelatedParties | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC exc:GenerationNewEngland | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | -768.0 | -781.0 | -873.0 | -833.0 | -748.0 | -816.0 | -863.0 | -759.0 | -744.0 | -783.0 | -874.0 | -790.0 | -790.0 | -886.0 |
| Percentage of OperatingExpenses | -10.2 | -7.7 | -11.1 | -10.3 | -11.1 | -10.8 | -11.7 | -10.0 | -10.8 | -9.5 | -10.8 | -9.6 | -11.1 | -10.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -83300.0 | -74800.0 | -81600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:IntersegmentElimination | 96.7 | 97.7 | 0.0 | 98.6 | 98.4 | 99.0 | 0.0 | 99.3 | 99.2 | 99.7 | 0.0 | 101.4 | 101.8 | 101.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 537 | 492 | 595 | 489 | 478 | 481 | 591 | 457 | 484 | 459 | 534 | 459 | 492 | 444 |
| Percentage of OperatingExpenses | 7.1 | 4.9 | 7.6 | 6.0 | 7.1 | 6.4 | 8.0 | 6.0 | 7.0 | 5.6 | 6.6 | 5.6 | 6.9 | 5.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 48900.0 | 47800.0 | 48100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:CorporateNonSegment us-gaap:CorporateAndOther | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 269 | 282 | 276 | 338 | 258 | 251 | 251 | 340 | 246 | 252 | 240 | 322 | 240 | 287 |
| Percentage of OperatingExpenses | 3.6 | 2.8 | 3.5 | 4.2 | 3.8 | 3.3 | 3.4 | 4.5 | 3.6 | 3.1 | 3.0 | 3.9 | 3.4 | 3.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 33800.0 | 25800.0 | 25100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:AtlanticCityElectricCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 620 | 752 | 695 | 642 | 573 | 688 | 638 | 612 | 569 | 756 | 691 | 628 | 578 | 800 |
| Percentage of OperatingExpenses | 8.2 | 7.5 | 8.9 | 7.9 | 8.5 | 9.1 | 8.6 | 8.1 | 8.3 | 9.2 | 8.5 | 7.6 | 8.1 | 9.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 64200.0 | 57300.0 | 68800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:BaltimoreGasAndElectricCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 1196 | 1210 | 1152 | 1302 | 1345 | 1151 | 1149 | 1256 | 1040 | 1135 | 1131 | 1275 | 1111 | 1223 |
| Percentage of OperatingExpenses | 15.8 | 12.0 | 14.7 | 16.1 | 19.9 | 15.3 | 15.5 | 16.6 | 15.1 | 13.7 | 14.0 | 15.5 | 15.6 | 14.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 130200.0 | 134500.0 | 115100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:CommonwealthEdisonCo | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 255 | 309 | 277 | 296 | 263 | 284 | 269 | 268 | 243 | 308 | 284 | 277 | 247 | 335 |
| Percentage of OperatingExpenses | 3.4 | 3.1 | 3.5 | 3.7 | 3.9 | 3.8 | 3.6 | 3.5 | 3.5 | 3.7 | 3.5 | 3.4 | 3.5 | 3.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 29600.0 | 26300.0 | 28400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:DelmarvaPowerandLightCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 4469 | 6672 | 4684 | 4727 | 3547 | 4400 | 4295 | 4274 | 4096 | 4963 | 5035 | 4961 | 4298 | 5218 |
| Percentage of OperatingExpenses | 59.1 | 66.2 | 59.6 | 58.5 | 52.4 | 58.4 | 58.1 | 56.5 | 59.5 | 60.1 | 62.1 | 60.1 | 60.2 | 60.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 472700.0 | 354700.0 | 440000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ExelonGenerationCoLLC | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 552 | 679 | 612 | 658 | 618 | 625 | 605 | 595 | 510 | 678 | 599 | 603 | 526 | 724 |
| Percentage of OperatingExpenses | 7.3 | 6.7 | 7.8 | 8.1 | 9.1 | 8.3 | 8.2 | 7.9 | 7.4 | 8.2 | 7.4 | 7.3 | 7.4 | 8.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 65800.0 | 61800.0 | 62500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PecoEnergyCo | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 955 | 1058 | 988 | 1102 | 956 | 1000 | 978 | 1124 | 926 | 1054 | 991 | 1116 | 923 | 1125 |
| Percentage of OperatingExpenses | 12.6 | 10.5 | 12.6 | 13.6 | 14.1 | 13.3 | 13.2 | 14.9 | 13.5 | 12.8 | 12.2 | 13.5 | 12.9 | 13.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 110200.0 | 95600.0 | 100000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PepcoHoldingsLLC | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 429 | 466 | 435 | 465 | 436 | 462 | 455 | 515 | 438 | 491 | 465 | 516 | 438 | 501 |
| Percentage of OperatingExpenses | 5.7 | 4.6 | 5.5 | 5.7 | 6.4 | 6.1 | 6.2 | 6.8 | 6.4 | 5.9 | 5.7 | 6.3 | 6.1 | 5.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 46500.0 | 43600.0 | 46200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PotomacElectricPowerCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 366 | -121.0 | 269 | 769 | 565 | 1220 | 962 | 1353 | 841 | 1218 | 708 | 1146 | 942 | 1101 | 1258 | 1475 | 232 | 1296 | 714 | 1267 | 647 | 483 | 707 | 1200 | 1134 | 1366 | 705 | 1400 | 829 | 163 | 889 | 1254 | 1005 | 508 | 704 | 603 | 714 | 359 | 1062 | 1181 | 1034 | 1202 | 939 | 1367 | 1018 | 1402 | 1076 | 1403 | 1016 | 1255 |
| Percentage of OperatingIncomeLoss | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 76900.0 | 56500.0 | 122000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 126700.0 | 64700.0 | 0.0 | 0.0 | 60000.0 | 113400.0 | 136600.0 | 0.0 | 0.0 | 0.0 | 16300.0 | 0.0 | 62700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 50 | 28 | 17 | 82 | -2.0 | 27 | 23 | 79 | 28 | 21 | 14 | 84 | 25 | 23 | 28 | 79 | 25 | 25 | 26 | 83 | 19 | -121.0 | 29 | 51 | 25 | 29 |
| Percentage of OperatingIncomeLoss | 13.7 | -23.1 | 6.3 | 10.7 | -0.4 | 2.2 | 2.4 | 5.8 | 3.3 | 1.7 | 2.0 | 7.3 | 2.7 | 2.1 | 2.2 | 5.4 | 10.8 | 1.9 | 3.6 | 6.6 | 2.9 | -25.1 | 4.1 | 4.2 | 2.2 | 2.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 8200.0 | -200.0 | 2700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 8300.0 | 1900.0 | 0.0 | 0.0 | 2550.0 | 2500.0 | 2900.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 5000.0 | 2800.0 | 0.0 | 8200.0 | -200.0 | 2700.0 | 0.0 | 7900.0 | 2800.0 | 2100.0 | 0.0 | 8400.0 | 2500.0 | 2300.0 | 0.0 | 0.0 | 2500.0 | 2500.0 | 0.0 | 8300.0 | 1900.0 | -12100.0 | 0.0 | 5100.0 | 2500.0 | 2900.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | 62 | 222 | 119 | 89 | 43 | 249 | 142 | 91 | 80 | 220 | 109 | 103 | 85 | 177 | 163 | 124 | 98 | 228 | 190 | 115 | 59 | 187 | 144 | 110 | 99 | 204 | 113 | 102 | 55 | 169 | 101 | 114 | 69 | 163 | 61 | 30 | 52 | -11.0 | 84 | 23 | 54 | 153 |
| Percentage of OperatingIncomeLoss | 16.9 | -183.5 | 44.2 | 11.6 | 7.6 | 20.4 | 14.8 | 6.7 | 9.5 | 18.1 | 15.4 | 9.0 | 9.0 | 16.1 | 13.0 | 8.4 | 42.2 | 17.6 | 26.6 | 9.1 | 9.1 | 38.7 | 20.4 | 9.2 | 8.7 | 14.9 | 16.0 | 7.3 | 6.6 | 103.7 | 11.4 | 9.1 | 6.9 | 32.1 | 8.7 | 5.0 | 7.3 | -3.1 | 7.9 | 1.9 | 5.2 | 12.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 8900.0 | 4300.0 | 24900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 11500.0 | 5900.0 | 0.0 | 0.0 | 5500.0 | 9900.0 | 20400.0 | 0.0 | 0.0 | 0.0 | 16900.0 | 0.0 | 5700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 885.7 | 3700.0 | 0.0 | 1483.3 | 1075.0 | 4150.0 | 0.0 | 1516.7 | 1333.3 | 3666.7 | 0.0 | 1716.7 | 1416.7 | 2950.0 | 0.0 | 4133.3 | 3266.7 | 4560.0 | 0.0 | 1642.9 | 1475.0 | 3740.0 | 0.0 | 3666.7 | 9900.0 | 2914.3 | 0.0 | 3400.0 | 2750.0 | 1056.2 | 0.0 | 5700.0 | 1725.0 | 4075.0 | 0.0 | 750.0 | 2600.0 | -366.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 321 | 325 | 253 | 341 | 72 | 288 | 255 | 328 | 311 | 276 | 242 | 323 | 288 | 292 | 286 | 404 | 319 | 314 | 217 | 389 | 324 | 274 | 217 | 327 | 243 | 230 | 197 | 287 | 258 | 238 | 236 | 278 | 232 | 209 | 300 | 218 | 142 | 226 | 285 | 243 | 254 | 200 | 229 | 280 | 256 | 291 | 224 | 203 | 209 | 206 |
| Percentage of OperatingIncomeLoss | 87.7 | -268.6 | 94.1 | 44.3 | 12.7 | 23.6 | 26.5 | 24.2 | 37.0 | 22.7 | 34.2 | 28.2 | 30.6 | 26.5 | 22.7 | 27.4 | 137.5 | 24.2 | 30.4 | 30.7 | 50.1 | 56.7 | 30.7 | 27.2 | 21.4 | 16.8 | 27.9 | 20.5 | 31.1 | 146.0 | 26.5 | 22.2 | 23.1 | 41.1 | 42.6 | 36.2 | 19.9 | 63.0 | 26.8 | 20.6 | 24.6 | 16.6 | 24.4 | 20.5 | 25.1 | 20.8 | 20.8 | 14.5 | 20.6 | 16.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 34100.0 | 7200.0 | 28800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 38900.0 | 32400.0 | 0.0 | 0.0 | 16350.0 | 24300.0 | 23000.0 | 0.0 | 0.0 | 0.0 | 23800.0 | 0.0 | 13900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 6420.0 | 5416.7 | 0.0 | 2273.3 | 654.5 | 5760.0 | 0.0 | 8200.0 | 6220.0 | 6900.0 | 0.0 | 8075.0 | 5760.0 | 2085.7 | 0.0 | 13466.7 | 10633.3 | 6280.0 | 0.0 | 9725.0 | 10800.0 | 5480.0 | 0.0 | 32700.0 | 24300.0 | 23000.0 | 0.0 | 28700.0 | 0.0 | 23800.0 | 0.0 | 27800.0 | 0.0 | 20900.0 | 0.0 | 0.0 | 14200.0 | 22600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 43 | 73 | 40 | 41 | 4.0 | 66 | 50 | 51 | 44 | 72 | 48 | 51 | 42 | 49 | 52 | 59 | 41 | 78 | 20 | 72 | 30 | -72.0 | 46 | 32 | 24 | 63 |
| Percentage of OperatingIncomeLoss | 11.7 | -60.3 | 14.9 | 5.3 | 0.7 | 5.4 | 5.2 | 3.8 | 5.2 | 5.9 | 6.8 | 4.5 | 4.5 | 4.5 | 4.1 | 4.0 | 17.7 | 6.0 | 2.8 | 5.7 | 4.6 | -14.9 | 6.5 | 2.7 | 2.1 | 4.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 4100.0 | 400.0 | 6600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 7200.0 | 3000.0 | 0.0 | 0.0 | 1600.0 | 2400.0 | 6300.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 2150.0 | 3650.0 | 0.0 | 1366.7 | 200.0 | 3300.0 | 0.0 | 5100.0 | 2200.0 | 3600.0 | 0.0 | 2550.0 | 2100.0 | 2450.0 | 0.0 | 2950.0 | 2050.0 | 3900.0 | 0.0 | 3600.0 | 1500.0 | -3600.0 | 0.0 | 3200.0 | 1200.0 | 3150.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | -308.0 | -1042.0 | -354.0 | -68.0 | 345 | 333 | 362 | 482 | 147 | 333 | 35 | 311 | 282 | 347 | 501 | 500 | -467.0 | 387 | 94 | 342 | -13.0 | 415 | 230 | 622 | 703 | 719 | 249 | 887 | 429 | -389.0 | 405 | 721 | 603 | -64.0 | 290 | 174 | 384 | 272 | 673 | 754 | 647 | 801 | 660 | 883 | 587 | 916 | 711 | 1046 | 676 | 862 |
| Percentage of OperatingIncomeLoss | -84.2 | 861.2 | -131.6 | -8.8 | 61.1 | 27.3 | 37.6 | 35.6 | 17.5 | 27.3 | 4.9 | 27.1 | 29.9 | 31.5 | 39.8 | 33.9 | -201.3 | 29.9 | 13.2 | 27.0 | -2.0 | 85.9 | 32.5 | 51.8 | 62.0 | 52.6 | 35.3 | 63.4 | 51.7 | -238.7 | 45.6 | 57.5 | 60.0 | -12.6 | 41.2 | 28.9 | 53.8 | 75.8 | 63.4 | 63.8 | 62.6 | 66.6 | 70.3 | 64.6 | 57.7 | 65.3 | 66.1 | 74.6 | 66.5 | 68.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -6800.0 | 34500.0 | 33300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 34200.0 | -1300.0 | 0.0 | 0.0 | 31100.0 | 70300.0 | 71900.0 | 0.0 | 0.0 | 0.0 | -38900.0 | 0.0 | 36050.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | -121.3 | -353.2 | 0.0 | -20.5 | 127.3 | 100.9 | 0.0 | 175.3 | 58.3 | 105.0 | 0.0 | 101.0 | 103.3 | 87.2 | 0.0 | 168.9 | -174.3 | 117.3 | 0.0 | 68.1 | -3.6 | 154.9 | 0.0 | 301.9 | 459.5 | 340.8 | 0.0 | 792.0 | 213.4 | -116.5 | 0.0 | 187.8 | 171.3 | -16.3 | 0.0 | 36.8 | 91.4 | 73.5 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 141 | 210 | 140 | 155 | 63 | 188 | 162 | 183 | 145 | 222 | 165 | 154 | 127 | 142 | 157 | 169 | 137 | 192 | 150 | 204 | 152 | 196 | 128 | 154 | 124 | 223 | 155 | 133 | 134 | 149 | 170 | 155 | 138 | 203 | 117 | 178 | 151 | 177 | 131 | 153 | 161 | 210 | 70 | 215 | 182 | 194 | 160 | 172 | 154 | 210 |
| Percentage of OperatingIncomeLoss | 38.5 | -173.6 | 52.0 | 20.2 | 11.2 | 15.4 | 16.8 | 13.5 | 17.2 | 18.2 | 23.3 | 13.4 | 13.5 | 12.9 | 12.5 | 11.5 | 59.1 | 14.8 | 21.0 | 16.1 | 23.5 | 40.6 | 18.1 | 12.8 | 10.9 | 16.3 | 22.0 | 9.5 | 16.2 | 91.4 | 19.1 | 12.4 | 13.7 | 40.0 | 16.6 | 29.5 | 21.1 | 49.3 | 12.3 | 13.0 | 15.6 | 17.5 | 7.5 | 15.7 | 17.9 | 13.8 | 14.9 | 12.3 | 15.2 | 16.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 15500.0 | 6300.0 | 18800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 20400.0 | 15200.0 | 0.0 | 0.0 | 7700.0 | 12400.0 | 22300.0 | 0.0 | 0.0 | 0.0 | 14900.0 | 0.0 | 7750.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 7050.0 | 10500.0 | 0.0 | 5166.7 | 3150.0 | 9400.0 | 0.0 | 18300.0 | 7250.0 | 22200.0 | 0.0 | 7700.0 | 6350.0 | 7100.0 | 0.0 | 8450.0 | 6850.0 | 19200.0 | 0.0 | 10200.0 | 7600.0 | 19600.0 | 0.0 | 15400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 14900.0 | 0.0 | 15500.0 | 0.0 | 0.0 | 0.0 | 17800.0 | 15100.0 | 17700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 185 | 186 | 130 | 266 | 60 | 173 | 128 | 256 | 165 | 175 | 126 | 245 | 153 | 126 | 159 | 285 | 148 | 180 |
| Percentage of OperatingIncomeLoss | 50.5 | -153.7 | 48.3 | 34.6 | 10.6 | 14.2 | 13.3 | 18.9 | 19.6 | 14.4 | 17.8 | 21.4 | 16.2 | 11.4 | 12.6 | 19.3 | 63.8 | 13.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 26600.0 | 6000.0 | 17300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 4625.0 | 6200.0 | 0.0 | 4433.3 | 2000.0 | 5766.7 | 0.0 | 6400.0 | 5500.0 | 5833.3 | 0.0 | 8166.7 | 5100.0 | 3150.0 | 0.0 | 2375.0 | 1233.3 | 1500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 94 | 87 | 73 | 146 | 58 | 82 | 57 | 127 | 93 | 84 | 65 | 112 | 85 | 56 | 87 | 149 | 84 | 79 | 51 | 132 | 97 | -105.0 | 123 | 115 | 83 | 63 |
| Percentage of OperatingIncomeLoss | 25.7 | -71.9 | 27.1 | 19.0 | 10.3 | 6.7 | 5.9 | 9.4 | 11.1 | 6.9 | 9.2 | 9.8 | 9.0 | 5.1 | 6.9 | 10.1 | 36.2 | 6.1 | 7.1 | 10.4 | 15.0 | -21.7 | 17.4 | 9.6 | 7.3 | 4.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 14600.0 | 5800.0 | 8200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 13200.0 | 9700.0 | 0.0 | 0.0 | 5750.0 | 8300.0 | 6300.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 9400.0 | 8700.0 | 0.0 | 4866.7 | 5800.0 | 8200.0 | 0.0 | 6350.0 | 9300.0 | 4200.0 | 0.0 | 5600.0 | 4250.0 | 2800.0 | 0.0 | 14900.0 | 8400.0 | 7900.0 | 0.0 | 13200.0 | 9700.0 | -10500.0 | 0.0 | 11500.0 | 8300.0 | 6300.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 |
| Value | 57 | 54 | -296.0 | 28 | 41 | 21 | -231.0 | 30 | 21 | -18.0 | -127.0 | 52 | 44 | 72 | 102 | 44 | 35 | -12.0 | -132.0 | 36 | 31 | 28 | -28.0 | 32 | 50 | 11 | -767.0 | -11.0 | 131 | 4.0 | 621 | 12 | 0.0 | 94 | -362.0 | -92.0 | -114.0 | 251 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 2800.0 | 4100.0 | 2100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 3600.0 | 3100.0 | 0.0 | 0.0 | 1600.0 | 5000.0 | 1100.0 | 0.0 | 0.0 | 0.0 | 400.0 | 0.0 | 600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 |
| Value | 2.0 | 1.0 | 6.0 | 3.0 | 2.0 | -9.0 | 4.0 | 3.0 | -1.0 | 1.0 | -8.0 | 2.0 | 2.0 | 7.0 | -1.0 | 4.0 | 1.0 | 11 | 7.0 | 4.0 | 0.0 | -1.0 | -3.0 | -13.0 | 6.0 | -17.0 | -47.0 | -26.0 | -155.0 | -21.0 | -29.0 | -32.0 | -134.0 | -104.0 | -239.0 | -152.0 | -263.0 | 252 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 3.5 | 1.9 | -2.0 | 10.7 | 4.9 | -42.9 | -1.7 | 10.0 | -4.8 | -5.6 | 6.3 | 3.8 | 4.5 | 9.7 | -1.0 | 9.1 | 2.9 | -91.7 | -5.3 | 11.1 | 0.0 | -3.6 | 10.7 | -40.6 | 12.0 | -154.5 | 6.1 | 236.4 | -118.3 | -525.0 | -4.7 | -266.7 | 0.0 | -110.6 | 66.0 | 165.2 | 230.7 | 100.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 300.0 | 200.0 | -900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 400.0 | 0.0 | 0.0 | 0.0 | -650.0 | 600.0 | -1700.0 | 0.0 | 0.0 | 0.0 | -2100.0 | 0.0 | -1600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 0.8 | 0.3 | 0.0 | 0.9 | 0.7 | -2.7 | 0.0 | 1.1 | -0.4 | 0.3 | 0.0 | 0.6 | 0.7 | 1.8 | 0.0 | 1.4 | 0.4 | 3.3 | 0.0 | 0.8 | 0.0 | -0.4 | 0.0 | -6.3 | 3.9 | -8.1 | 0.0 | -23.2 | -77.1 | -6.3 | 0.0 | -8.3 | -38.1 | -26.5 | 0.0 | -32.1 | -62.6 | 68.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 |
| Value | 2.0 | 1.0 | 3.0 | 2.0 | -9.0 | 0.0 | 2.0 | -7.0 | 2.0 | 1.0 | 6.0 | -1.0 | 4.0 | 1.0 | 13 | 2.0 | 9.0 | -1.0 | -1.0 | -40.0 | -21.0 | -29.0 | -32.0 | -134.0 | -104.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 3.5 | 1.9 | 10.7 | 4.9 | -42.9 | 0.0 | -11.1 | 5.5 | 3.8 | 2.3 | 8.3 | -1.0 | 9.1 | 2.9 | -108.3 | -1.5 | 25.0 | -3.2 | -3.6 | -30.5 | -525.0 | -4.7 | -266.7 | 0.0 | -110.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 300.0 | 200.0 | -900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 900.0 | -100.0 | 0.0 | 0.0 | -2100.0 | 0.0 | -1600.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC us-gaap:AccumulatedOtherComprehensiveIncome | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 |
| Value | 55 | 53 | -302.0 | 26 | 39 | 30 | -235.0 | 27 | 21 | -18.0 | -120.0 | 50 | 46 | 62 | 101 | 38 | 35 | -23.0 | -147.0 | 35 | 34 | 33 | -26.0 | 43 | 41 | 17 | -711.0 | 19 | 290 | 22 | 647 | 42 | 62 | 126 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 96.5 | 98.1 | 102.0 | 92.9 | 95.1 | 142.9 | 101.7 | 90.0 | 100.0 | 100.0 | 94.5 | 96.2 | 104.5 | 86.1 | 99.0 | 86.4 | 100.0 | 191.7 | 111.4 | 97.2 | 109.7 | 117.9 | 92.9 | 134.4 | 82.0 | 154.5 | 92.7 | -172.7 | 221.4 | 550.0 | 104.2 | 350.0 | 0.0 | 134.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 2600.0 | 3900.0 | 3000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 3500.0 | 3400.0 | 0.0 | 0.0 | 2150.0 | 4100.0 | 1700.0 | 0.0 | 0.0 | 0.0 | 2200.0 | 0.0 | 2100.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:AccumulatedDefinedBenefitPlansAdjustment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 |
| Value | -1.0 | -1.0 | 0.0 | -1.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 4.0 | 8.0 | -2.0 | 0.0 | -1.0 | 6.0 | 6.0 | 3.0 | 0.0 | -7.0 | 5.0 | -5.0 | 3.0 | 6.0 | -56.0 | -19.0 | -48.0 | -25.0 | -79.0 | -46.0 | -65.0 | -58.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 0.3 | -3.6 | 0.0 | -4.8 | -0.0 | 0.0 | 0.0 | -0.0 | -0.0 | 0.0 | 9.1 | 11.1 | -2.0 | 0.0 | -2.9 | -50.0 | -4.5 | 8.3 | 0.0 | -25.0 | -17.9 | -15.6 | 6.0 | 54.5 | 7.3 | 172.7 | -36.6 | -625.0 | -12.7 | -383.3 | 0.0 | -61.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | -100.0 | 0.0 | -100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 300.0 | 0.0 | 0.0 | 0.0 | -250.0 | 300.0 | 600.0 | 0.0 | 0.0 | 0.0 | -2500.0 | 0.0 | -2300.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2013-06-30 | 2013-03-31 |
| Value | 57 | 54 | -296.0 | 28 | 41 | 21 | -231.0 | 27 | 22 | -17.0 | -126.0 | 52 | 44 | 71 | 102 | 44 | 37 | -10.0 | -137.0 | 42 | 31 | 28 | 0.0 | 94 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 90.0 | 104.8 | 94.4 | 99.2 | 100.0 | 100.0 | 98.6 | 100.0 | 100.0 | 105.7 | 83.3 | 103.8 | 116.7 | 100.0 | 100.0 | 0.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 2800.0 | 4100.0 | 2100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 4200.0 | 3100.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:AccumulatedOtherComprehensiveIncome | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 |
| Value | 2.0 | 1.0 | 7.0 | 3.0 | 2.0 | -8.0 | 4.0 | -2.0 | 2.0 | 2.0 | -6.0 | 2.0 | -7.0 | 1.0 | 0.0 | 4.0 | 2.0 | 1.0 | 2.0 | 2.0 | 0.0 | 6.0 | -4.0 | -8.0 | 3.0 | -12.0 | -3.0 | -5.0 | 4.0 | -5.0 | -5.0 | 1.0 | -5.0 | -1.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 3.5 | 1.9 | -2.4 | 10.7 | 4.9 | -38.1 | -1.7 | -6.7 | 9.5 | -11.1 | 4.7 | 3.8 | -15.9 | 1.4 | 0.0 | 9.1 | 5.7 | -8.3 | -1.5 | 5.6 | 0.0 | 21.4 | 14.3 | -25.0 | 6.0 | -109.1 | 0.4 | 45.5 | 3.1 | -125.0 | -0.8 | 8.3 | 0.0 | -1.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 300.0 | 200.0 | -800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 200.0 | 0.0 | 0.0 | 0.0 | -400.0 | 300.0 | -1200.0 | 0.0 | 0.0 | 0.0 | -500.0 | 0.0 | 50.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:AccumulatedTranslationAdjustment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 28 | 41 | 21 | 27 | 21 | -18.0 | 52 | 45 | 72 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 100.0 | 100.0 | 100.0 | 90.0 | 100.0 | 100.0 | 100.0 | 102.3 | 100.0 |
| Percentage of RevenueFromRelatedParties | 2800.0 | 4100.0 | 2100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OtherComprehensiveIncome | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 581 | 225 | 793 | 421 | 656 | -725.0 | 390 | 158 | 212 | 467 | -324.0 | 194 | 44 | -28.0 | 331 | 237 | 205 | 283 | 36 | 120 | 144 | 114 | 133 | -244.0 | -17.0 | 80 | -247.0 | 354 | 243 | 103 | 162 | 155 | -17.0 | 172 | 93 | 101 | -43.0 | 194 | 148 | -143.0 | 100 | 93 | 134 | 206 | -122.0 | 93 |
| Percentage of OtherNonoperatingIncomeExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 42100.0 | 65600.0 | -72500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 12000.0 | 14400.0 | 0.0 | 0.0 | -12200.0 | -1700.0 | 8000.0 | 0.0 | 0.0 | 0.0 | 10300.0 | 0.0 | 7750.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 1.0 | 1.0 | 1.0 | 1.0 | 2.0 | 2.0 | 1.0 | 1.0 | 1.0 | 3.0 | 0.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 2.0 | 2.0 | 1.0 | 2.0 | 2.0 | 4.0 | -1.0 | 1.0 | 1.0 | 1.0 |
| Percentage of OtherNonoperatingIncomeExpense | 0.2 | 0.4 | 0.1 | 0.2 | 0.3 | -0.3 | 0.3 | 0.6 | 0.5 | 0.6 | -0.0 | 0.5 | 2.3 | -3.6 | 0.3 | 0.4 | 1.0 | 0.7 | 2.8 | 1.7 | 1.4 | 3.5 | -0.8 | -0.4 | -5.9 | 1.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 100.0 | 200.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 200.0 | 200.0 | 0.0 | 0.0 | 50.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 100.0 | 100.0 | 0.0 | 100.0 | 200.0 | 200.0 | 0.0 | 100.0 | 100.0 | 300.0 | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 0.0 | 200.0 | 200.0 | 0.0 | 200.0 | 200.0 | 400.0 | 0.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | 9.0 | 8.0 | 6.0 | 6.0 | 6.0 | 5.0 | 10.0 | 7.0 | 5.0 | 5.0 | 5.0 | 5.0 | 4.0 | 4.0 | 4.0 | 4.0 | 4.0 | 4.0 | 5.0 | 5.0 | 5.0 | 4.0 | 5.0 | 4.0 | 4.0 | 4.0 | 4.0 | 4.0 | 5.0 | 4.0 | 4.0 | 4.0 | 4.0 | 5.0 | 5.0 | 5.0 | 7.0 | 6.0 | 4.0 | 8.0 | 6.0 | 8.0 |
| Percentage of OtherNonoperatingIncomeExpense | 1.5 | 3.6 | 0.8 | 1.4 | 0.9 | -0.7 | 2.6 | 4.4 | 2.4 | 1.1 | -1.5 | 2.6 | 9.1 | -14.3 | 1.2 | 1.7 | 2.0 | 1.4 | 13.9 | 4.2 | 3.5 | 3.5 | 3.8 | -1.6 | -23.5 | 5.0 | -1.6 | 1.1 | 2.1 | 3.9 | 2.5 | 2.6 | -23.5 | 2.9 | 5.4 | 5.0 | -16.3 | 3.1 | 2.7 | -5.6 | 6.0 | 8.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 600.0 | 600.0 | 500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 500.0 | 500.0 | 0.0 | 0.0 | 200.0 | 400.0 | 400.0 | 0.0 | 0.0 | 0.0 | 400.0 | 0.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 128.6 | 133.3 | 0.0 | 100.0 | 150.0 | 83.3 | 0.0 | 116.7 | 83.3 | 83.3 | 0.0 | 83.3 | 66.7 | 66.7 | 0.0 | 133.3 | 133.3 | 80.0 | 0.0 | 71.4 | 125.0 | 80.0 | 0.0 | 133.3 | 400.0 | 57.1 | 0.0 | 133.3 | 250.0 | 25.0 | 0.0 | 200.0 | 100.0 | 125.0 | 0.0 | 125.0 | 350.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 15 | 7.0 | 11 | 10.0 | 11 | 10.0 | 12 | 8.0 | 10.0 | 8.0 | 12 | 7.0 | 4.0 | 8.0 | 8.0 | 5.0 | 4.0 | 4.0 | 7.0 | -80.0 | 3.0 | 4.0 | 7.0 | 4.0 | 5.0 | 3.0 | 3.0 | 4.0 | 5.0 | 5.0 | 8.0 | 7.0 | 6.0 | 5.0 | 27 | 5.0 | 3.0 | 4.0 | 5.0 | 16 | 4.0 | 4.0 | 10.0 | 3.0 | 8.0 | 3.0 |
| Percentage of OtherNonoperatingIncomeExpense | 2.6 | 3.1 | 1.4 | 2.4 | 1.7 | -1.4 | 3.1 | 5.1 | 4.7 | 1.7 | -3.7 | 3.6 | 9.1 | -28.6 | 2.4 | 2.1 | 2.0 | 1.4 | 19.4 | -66.7 | 2.1 | 3.5 | 5.3 | -1.6 | -29.4 | 3.8 | -1.2 | 1.1 | 2.1 | 4.9 | 4.9 | 4.5 | -35.3 | 2.9 | 29.0 | 5.0 | -7.0 | 2.1 | 3.4 | -11.2 | 4.0 | 4.3 | 7.5 | 1.5 | -6.6 | 3.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 1000.0 | 1100.0 | 1000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -8000.0 | 300.0 | 0.0 | 0.0 | 200.0 | 500.0 | 300.0 | 0.0 | 0.0 | 0.0 | 500.0 | 0.0 | 350.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 300.0 | 116.7 | 0.0 | 66.7 | 100.0 | 200.0 | 0.0 | 200.0 | 200.0 | 200.0 | 0.0 | 175.0 | 80.0 | 57.1 | 0.0 | 166.7 | 133.3 | 80.0 | 0.0 | -2000.0 | 100.0 | 80.0 | 0.0 | 400.0 | 500.0 | 300.0 | 0.0 | 400.0 | 0.0 | 500.0 | 0.0 | 700.0 | 0.0 | 500.0 | 0.0 | 0.0 | 300.0 | 400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 4.0 | 3.0 | 3.0 | 2.0 | 2.0 | 2.0 | 3.0 | 2.0 | 5.0 | 3.0 | 3.0 | 2.0 | 3.0 | 2.0 | 4.0 | 4.0 | 3.0 | 3.0 | 4.0 | 3.0 | 3.0 | 3.0 | 2.0 | 4.0 | 2.0 | 2.0 |
| Percentage of OtherNonoperatingIncomeExpense | 0.7 | 1.3 | 0.4 | 0.5 | 0.3 | -0.3 | 0.8 | 1.3 | 2.4 | 0.6 | -0.9 | 1.0 | 6.8 | -7.1 | 1.2 | 1.7 | 1.5 | 1.1 | 11.1 | 2.5 | 2.1 | 2.6 | 1.5 | -1.6 | -11.8 | 2.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 200.0 | 200.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 300.0 | 300.0 | 0.0 | 0.0 | 200.0 | 200.0 | 200.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 200.0 | 150.0 | 0.0 | 66.7 | 100.0 | 100.0 | 0.0 | 200.0 | 250.0 | 150.0 | 0.0 | 100.0 | 150.0 | 100.0 | 0.0 | 200.0 | 150.0 | 150.0 | 0.0 | 150.0 | 150.0 | 150.0 | 0.0 | 400.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 508 | 167 | 738 | 367 | 602 | -771.0 | 294 | 128 | 171 | 430 | -342.0 | 179 | 29 | -44.0 | 300 | 209 | 181 | 259 | 6.0 | 185 | 117 | 93 | 133 | -257.0 | -31.0 | 94 | -255.0 | 342 | 228 | 90 | 139 | 134 | -33.0 | 128 | 54 | 83 | -76.0 | 178 | 134 | -164.0 | 76 | 75 | 119 | 192 | -133.0 | 79 |
| Percentage of OtherNonoperatingIncomeExpense | 87.4 | 74.2 | 93.1 | 87.2 | 91.8 | 106.3 | 75.4 | 81.0 | 80.7 | 92.1 | 105.6 | 92.3 | 65.9 | 157.1 | 90.6 | 88.2 | 88.3 | 91.5 | 16.7 | 154.2 | 81.2 | 81.6 | 100.0 | 105.3 | 182.4 | 117.5 | 103.2 | 96.6 | 93.8 | 87.4 | 85.8 | 86.5 | 194.1 | 74.4 | 58.1 | 82.2 | 176.7 | 91.8 | 90.5 | 114.7 | 76.0 | 80.6 | 88.8 | 93.2 | 109.0 | 84.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 36700.0 | 60200.0 | -77100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 18500.0 | 11700.0 | 0.0 | 0.0 | -12850.0 | -3100.0 | 9400.0 | 0.0 | 0.0 | 0.0 | 9000.0 | 0.0 | 6700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 200.0 | 56.6 | 0.0 | 110.9 | 222.1 | -233.6 | 0.0 | 46.5 | 67.9 | 135.6 | 0.0 | 58.1 | 10.6 | -11.1 | 0.0 | 70.6 | 67.5 | 78.5 | 0.0 | 36.9 | 32.7 | 34.7 | 0.0 | -124.8 | -20.3 | 44.5 | 0.0 | 305.4 | 113.4 | 26.9 | 0.0 | 34.9 | -9.4 | 32.7 | 0.0 | 17.5 | -18.1 | 48.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 |
| Value | 7.0 | 5.0 | 6.0 | 6.0 | 5.0 | 3.0 | 5.0 | 4.0 | 3.0 | 4.0 | 4.0 | 2.0 | 0.0 | 2.0 | 3.0 | 2.0 | 2.0 | 2.0 | 2.0 | 2.0 | 2.0 | 2.0 | 2.0 | 1.0 | 1.0 | 2.0 | 2.0 | 2.0 | 1.0 | 2.0 | 2.0 | 1.0 | 0.0 | 3.0 | 2.0 | 2.0 | 2.0 | 2.0 | 3.0 | 3.0 | 3.0 | 6.0 | 2.0 | 3.0 | -1.0 | 4.0 |
| Percentage of OtherNonoperatingIncomeExpense | 1.2 | 2.2 | 0.8 | 1.4 | 0.8 | -0.4 | 1.3 | 2.5 | 1.4 | 0.9 | -1.2 | 1.0 | 0.0 | -7.1 | 0.9 | 0.8 | 1.0 | 0.7 | 5.6 | 1.7 | 1.4 | 1.8 | 1.5 | -0.4 | -5.9 | 2.5 | -0.8 | 0.6 | 0.4 | 1.9 | 1.2 | 0.6 | -0.0 | 1.7 | 2.2 | 2.0 | -4.7 | 1.0 | 2.0 | -2.1 | 3.0 | 6.5 | 1.5 | 1.5 | 0.8 | 4.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 600.0 | 500.0 | 300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 200.0 | 200.0 | 0.0 | 0.0 | 50.0 | 100.0 | 200.0 | 0.0 | 0.0 | 0.0 | 200.0 | 0.0 | 50.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 350.0 | 250.0 | 0.0 | 200.0 | 250.0 | 150.0 | 0.0 | 400.0 | 150.0 | 400.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 100.0 | 200.0 | 0.0 | 100.0 | 100.0 | 200.0 | 0.0 | 100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 200.0 | 0.0 | 100.0 | 0.0 | 0.0 | 0.0 | 200.0 | 200.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 20 | 17 | 15 | 16 | 14 | 13 | 16 | 13 | 14 | 12 | 10.0 | 11 | 11 | 11 | 14 | 13 | 13 | 13 |
| Percentage of OtherNonoperatingIncomeExpense | 3.4 | 7.6 | 1.9 | 3.8 | 2.1 | -1.8 | 4.1 | 8.2 | 6.6 | 2.6 | -3.1 | 5.7 | 25.0 | -39.3 | 4.2 | 5.5 | 6.3 | 4.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 1600.0 | 1400.0 | 1300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 500.0 | 566.7 | 0.0 | 266.7 | 466.7 | 433.3 | 0.0 | 325.0 | 466.7 | 400.0 | 0.0 | 366.7 | 366.7 | 275.0 | 0.0 | 108.3 | 108.3 | 108.3 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 13 | 12 | 10.0 | 10.0 | 9.0 | 9.0 | 9.0 | 9.0 | 7.0 | 7.0 | 8.0 | 7.0 | 8.0 | 8.0 | 10.0 | 7.0 | 7.0 | 8.0 | 8.0 | 12 | 6.0 | 9.0 | 7.0 | 8.0 | 8.0 | 5.0 |
| Percentage of OtherNonoperatingIncomeExpense | 2.2 | 5.3 | 1.3 | 2.4 | 1.4 | -1.2 | 2.3 | 5.7 | 3.3 | 1.5 | -2.5 | 3.6 | 18.2 | -28.6 | 3.0 | 3.0 | 3.4 | 2.8 | 22.2 | 10.0 | 4.2 | 7.9 | 5.3 | -3.3 | -47.1 | 6.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 1000.0 | 900.0 | 900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 1200.0 | 600.0 | 0.0 | 0.0 | 400.0 | 800.0 | 500.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 1300.0 | 1200.0 | 0.0 | 333.3 | 900.0 | 900.0 | 0.0 | 450.0 | 700.0 | 350.0 | 0.0 | 350.0 | 400.0 | 400.0 | 0.0 | 700.0 | 700.0 | 800.0 | 0.0 | 1200.0 | 600.0 | 900.0 | 0.0 | 800.0 | 800.0 | 500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 |
| Value | 476 | -264.0 | 435 | 569 | 574 | 376 | 808 | 760 | 494 | 966 | 105 | 800 | 542 | 636 | 1938 | 867 | 64 | 981 | 248 | 526 | 306 | 123 | 309 | 587 | 633 | 738 | 18 | 1074 | 557 | 93 | 495 | 736 | 497 | 1.0 | 378 | 297 | 289 | 200 | 606 | 601 | 669 | 524 | 845 |
| Percentage of ProfitLoss | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 56900.0 | 57400.0 | 37600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 52600.0 | 30600.0 | 0.0 | 0.0 | 29350.0 | 63300.0 | 73800.0 | 0.0 | 0.0 | 0.0 | 9300.0 | 0.0 | 36800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-09-30 |
| Value | -5.0 | 8.0 | 56 | -5.0 | -8.0 | -10.0 | 43 | -4.0 | -8.0 | -5.0 | -3.0 | -4.0 | 6.0 | 3.0 | -1.0 | 6.0 | 2.0 |
| Percentage of RealizedInvestmentGainsLosses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -500.0 | -800.0 | -1000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 200.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo us-gaap:InterestRateSwap us-gaap:Derivative | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 129 | 72 | -11.0 | -122.0 | 67 | -57.0 | -80.0 | -13.0 | 4503 | 4055 | 4457 | 3797 | 4570 | 3946 | 4313 | 3715 | 4197 | 3793 | 4467 | 3676 | 3100 | 2584 | 2837 | 2434 | 3198 |
| Percentage of RegulatedOperatingRevenue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | -1100.0 | -12200.0 | 6700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 446700.0 | 367600.0 | 0.0 | 0.0 | 141850.0 | 243400.0 | 319800.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 11 | 8.0 | 5.0 | -26.0 | 1.0 | 0.0 | 1.0 | -2.0 | 1.0 | 0.0 | -1.0 | -1.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 8.5 | 11.1 | -45.5 | 21.3 | 1.5 | -0.0 | -1.2 | 15.4 | 0.0 | 0.0 | -0.0 | -0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 500.0 | -2600.0 | 100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 1100.0 | 0.0 | 500.0 | -2600.0 | 100.0 | 0.0 | 100.0 | -200.0 | 100.0 | 0.0 | -100.0 | -100.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 18 | 26 | -9.0 | -37.0 | 36 | 1.0 | -5.0 | 6.0 | 10.0 | -3.0 | -6.0 | -4.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 14.0 | 36.1 | 81.8 | 30.3 | 53.7 | -1.8 | 6.2 | -46.2 | 0.2 | -0.1 | -0.1 | -0.1 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | -900.0 | -3700.0 | 3600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 300.0 | 0.0 | -150.0 | -925.0 | 600.0 | 0.0 | -83.3 | 100.0 | 166.7 | 0.0 | -100.0 | -66.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 54 | 4.0 | -38.0 | -25.0 | 12 | -35.0 | -56.0 | -14.0 | -28.0 | -2.0 | -15.0 | -17.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 41.9 | 5.6 | 345.5 | 20.5 | 17.9 | 61.4 | 70.0 | 107.7 | -0.6 | -0.0 | -0.3 | -0.4 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | -3800.0 | -2500.0 | 1200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 900.0 | 0.0 | -253.3 | -227.3 | 240.0 | 0.0 | -1400.0 | -280.0 | -700.0 | 0.0 | -375.0 | -340.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 9.0 | 8.0 | 8.0 | -25.0 | 1.0 | -5.0 | -6.0 | 0.0 | 0.0 | -1.0 | 0.0 | 4.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 7.0 | 11.1 | -72.7 | 20.5 | 1.5 | 8.8 | 7.5 | -0.0 | 0.0 | -0.0 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 800.0 | -2500.0 | 100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 450.0 | 0.0 | 266.7 | -1250.0 | 50.0 | 0.0 | -600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 10.0 | 6.0 | 5.0 | 4.0 | 2.0 | -5.0 | -11.0 | -3.0 | -3.0 | -9.0 | 1.0 | 2.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 7.8 | 8.3 | -45.5 | -3.3 | 3.0 | 8.8 | 13.8 | 23.1 | -0.1 | -0.2 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 500.0 | 400.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 500.0 | 0.0 | 166.7 | 200.0 | 100.0 | 0.0 | -1100.0 | -150.0 | -300.0 | 0.0 | 50.0 | 100.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 46 | 36 | 31 | -64.0 | 18 | -18.0 | -9.0 | -3.0 | 15 | -14.0 | -5.0 | -7.0 | 33 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 35.7 | 50.0 | -281.8 | 52.5 | 26.9 | 31.6 | 11.2 | 23.1 | 0.3 | -0.3 | -0.1 | -0.2 | 0.8 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 3100.0 | -6400.0 | 1800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 1533.3 | 0.0 | 516.7 | -2133.3 | 600.0 | 0.0 | -225.0 | -100.0 | 500.0 | 0.0 | -166.7 | -233.3 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 26 | 20 | 18 | -13.0 | 15 | -13.0 | -3.0 | -1.0 | 14 | -13.0 | -4.0 | -10.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RegulatedOperatingRevenue | 20.2 | 27.8 | -163.6 | 10.7 | 22.4 | 22.8 | 3.8 | 7.7 | 0.3 | -0.3 | -0.1 | -0.3 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 1800.0 | -1300.0 | 1500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 2600.0 | 0.0 | 600.0 | -1300.0 | 1500.0 | 0.0 | -150.0 | -100.0 | 700.0 | 0.0 | -200.0 | -500.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 7915 | 9890 | 8114 | 8853 | 7322 | 8747 | 8343 | 8929 | 7689 | 9477 | 8814 | 9403 | 8076 | 9693 | 8381 | 8769 | 7623 | 8757 | 7875 | 9002 | 6910 | 7573 | 6702 | 7401 | 6514 | 8830 | 7255 | 6912 | 6024 | 7237 | 6163 | 6502 | 6141 | 6082 | 6284 | 6565 | 5954 | 4686 | 3991 | 5295 | 4587 | 5052 | 4494 | 5291 | 4398 | 4461 | 4116 | 4339 | 4141 | 4722 |
| Percentage of Revenues | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 885300.0 | 732200.0 | 874700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 900200.0 | 691000.0 | 0.0 | 0.0 | 370050.0 | 651400.0 | 883000.0 | 0.0 | 0.0 | 0.0 | 723700.0 | 0.0 | 325100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 319 | 310 | 293 | 420 | 256 | 276 | 274 | 419 | 274 | 273 | 254 | 406 | 265 | 310 | 271 | 370 | 270 | 275 | 275 | 421 | 270 | 291 | 291 | 386 | 285 | 334 |
| Percentage of Revenues | 4.0 | 3.1 | 3.6 | 4.7 | 3.5 | 3.2 | 3.3 | 4.7 | 3.6 | 2.9 | 2.9 | 4.3 | 3.3 | 3.2 | 3.2 | 4.2 | 3.5 | 3.1 | 3.5 | 4.7 | 3.9 | 3.8 | 4.3 | 5.2 | 4.4 | 3.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 42000.0 | 25600.0 | 27600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 42100.0 | 27000.0 | 0.0 | 0.0 | 19300.0 | 28500.0 | 33400.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany | 31900.0 | 31000.0 | 0.0 | 42000.0 | 25600.0 | 27600.0 | 0.0 | 41900.0 | 27400.0 | 27300.0 | 0.0 | 40600.0 | 26500.0 | 31000.0 | 0.0 | 0.0 | 27000.0 | 27500.0 | 0.0 | 42100.0 | 27000.0 | 29100.0 | 0.0 | 38600.0 | 28500.0 | 33400.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 |
| Value | 682 | 974 | 814 | 731 | 616 | 937 | 779 | 703 | 649 | 976 | 799 | 731 | 662 | 977 | 813 | 738 | 674 | 951 | 812 | 812 | 680 | 929 | 746 | 725 | 628 | 1036 | 761 | 697 | 653 | 1054 | 794 | 737 | 653 | 880 | 703 | 720 | 616 | 696 | 673 | 745 | 674 | 976 |
| Percentage of Revenues | 8.6 | 9.8 | 10.0 | 8.3 | 8.4 | 10.7 | 9.3 | 7.9 | 8.4 | 10.3 | 9.1 | 7.8 | 8.2 | 10.1 | 9.7 | 8.4 | 8.8 | 10.9 | 10.3 | 9.0 | 9.8 | 12.3 | 11.1 | 9.8 | 9.6 | 11.7 | 10.5 | 10.1 | 10.8 | 14.6 | 12.9 | 11.3 | 10.6 | 14.5 | 11.2 | 11.0 | 10.3 | 14.9 | 16.9 | 14.1 | 14.7 | 19.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 73100.0 | 61600.0 | 93700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 81200.0 | 68000.0 | 0.0 | 0.0 | 36250.0 | 62800.0 | 103600.0 | 0.0 | 0.0 | 0.0 | 105400.0 | 0.0 | 36850.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany | 9742.9 | 16233.3 | 0.0 | 12183.3 | 15400.0 | 15616.7 | 0.0 | 11716.7 | 10816.7 | 16266.7 | 0.0 | 12183.3 | 11033.3 | 16283.3 | 0.0 | 24600.0 | 22466.7 | 19020.0 | 0.0 | 11600.0 | 17000.0 | 18580.0 | 0.0 | 24166.7 | 62800.0 | 14800.0 | 0.0 | 23233.3 | 32650.0 | 6587.5 | 0.0 | 36850.0 | 16325.0 | 22000.0 | 0.0 | 18000.0 | 30800.0 | 23200.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 1517 | 1535 | 1405 | 1643 | 1417 | 1439 | 1405 | 1583 | 1351 | 1408 | 1373 | 1598 | 1398 | 1512 | 1309 | 1571 | 1357 | 1298 | 1223 | 1497 | 1286 | 1249 | 1196 | 1376 | 1148 | 1185 | 1079 | 1222 | 1128 | 1134 | 1068 | 1156 | 1080 | 1160 | 1290 | 1484 | 1281 | 1388 | 1362 | 1784 | 1444 | 1466 | 1372 | 1918 | 1499 | 1415 | 1357 | 1475 | 1389 | 1553 |
| Percentage of Revenues | 19.2 | 15.5 | 17.3 | 18.6 | 19.4 | 16.5 | 16.8 | 17.7 | 17.6 | 14.9 | 15.6 | 17.0 | 17.3 | 15.6 | 15.6 | 17.9 | 17.8 | 14.8 | 15.5 | 16.6 | 18.6 | 16.5 | 17.8 | 18.6 | 17.6 | 13.4 | 14.9 | 17.7 | 18.7 | 15.7 | 17.3 | 17.8 | 17.6 | 19.1 | 20.5 | 22.6 | 21.5 | 29.6 | 34.1 | 33.7 | 31.5 | 29.0 | 30.5 | 36.3 | 34.1 | 31.7 | 33.0 | 34.0 | 33.5 | 32.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 164300.0 | 141700.0 | 143900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 149700.0 | 128600.0 | 0.0 | 0.0 | 68800.0 | 114800.0 | 118500.0 | 0.0 | 0.0 | 0.0 | 113400.0 | 0.0 | 57800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo | 30340.0 | 25583.3 | 0.0 | 10953.3 | 12881.8 | 28780.0 | 0.0 | 39575.0 | 27020.0 | 35200.0 | 0.0 | 39950.0 | 27960.0 | 10800.0 | 0.0 | 52366.7 | 45233.3 | 25960.0 | 0.0 | 37425.0 | 42866.7 | 24980.0 | 0.0 | 137600.0 | 114800.0 | 118500.0 | 0.0 | 122200.0 | 0.0 | 113400.0 | 0.0 | 115600.0 | 0.0 | 116000.0 | 0.0 | 0.0 | 128100.0 | 138800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 298 | 382 | 317 | 337 | 267 | 350 | 319 | 319 | 287 | 380 | 331 | 328 | 289 | 384 | 330 | 327 | 282 | 362 | 303 | 331 | 281 | 362 | 296 | 314 | 271 | 421 |
| Percentage of Revenues | 3.8 | 3.9 | 3.9 | 3.8 | 3.6 | 4.0 | 3.8 | 3.6 | 3.7 | 4.0 | 3.8 | 3.5 | 3.6 | 4.0 | 3.9 | 3.7 | 3.7 | 4.1 | 3.8 | 3.7 | 4.1 | 4.8 | 4.4 | 4.2 | 4.2 | 4.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 33700.0 | 26700.0 | 35000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 33100.0 | 28100.0 | 0.0 | 0.0 | 15700.0 | 27100.0 | 42100.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany | 14900.0 | 19100.0 | 0.0 | 11233.3 | 13350.0 | 17500.0 | 0.0 | 31900.0 | 14350.0 | 19000.0 | 0.0 | 16400.0 | 14450.0 | 19200.0 | 0.0 | 16350.0 | 14100.0 | 18100.0 | 0.0 | 16550.0 | 14050.0 | 18100.0 | 0.0 | 31400.0 | 13550.0 | 21050.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 4153 | 5559 | 4331 | 4659 | 3880 | 4733 | 4644 | 4774 | 4210 | 5296 | 5069 | 5278 | 4579 | 5512 | 4654 | 4751 | 4174 | 4888 | 4388 | 5035 | 3589 | 4739 | 4294 | 4768 | 4232 | 5840 | 4802 | 4412 | 3789 | 4390 | 3772 | 4255 | 4070 | 3533 | 3928 | 4017 | 3753 | 2739 | 2161 | 2862 | 2546 | 2739 | 2596 | 2655 | 2353 | 2421 | 2278 | 2445 | 2378 | 2601 |
| Percentage of Revenues | 52.5 | 56.2 | 53.4 | 52.6 | 53.0 | 54.1 | 55.7 | 53.5 | 54.8 | 55.9 | 57.5 | 56.1 | 56.7 | 56.9 | 55.5 | 54.2 | 54.8 | 55.8 | 55.7 | 55.9 | 51.9 | 62.6 | 64.1 | 64.4 | 65.0 | 66.1 | 66.2 | 63.8 | 62.9 | 60.7 | 61.2 | 65.4 | 66.3 | 58.1 | 62.5 | 61.2 | 63.0 | 58.5 | 54.1 | 54.1 | 55.5 | 54.2 | 57.8 | 50.2 | 53.5 | 54.3 | 55.3 | 56.3 | 57.4 | 55.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 465900.0 | 388000.0 | 473300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 503500.0 | 358900.0 | 0.0 | 0.0 | 238400.0 | 423200.0 | 584000.0 | 0.0 | 0.0 | 0.0 | 439000.0 | 0.0 | 212750.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:ExelonGenerationCoLLC | 1635.0 | 1884.4 | 0.0 | 1407.6 | 1431.7 | 1434.2 | 0.0 | 1736.0 | 1670.6 | 1670.7 | 0.0 | 1713.6 | 1677.3 | 1384.9 | 0.0 | 1605.1 | 1557.5 | 1481.2 | 0.0 | 1003.0 | 1002.5 | 1768.3 | 0.0 | 2314.6 | 2766.0 | 2767.8 | 0.0 | 3939.3 | 1885.1 | 1314.4 | 0.0 | 1108.1 | 1156.2 | 901.3 | 0.0 | 849.3 | 893.6 | 740.3 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2010-09-30 | 2010-06-30 | 2010-03-31 | 2009-12-31 | 2009-09-30 | 2009-06-30 | 2009-03-31 |
| Value | 693 | 889 | 752 | 813 | 681 | 813 | 766 | 778 | 655 | 900 | 765 | 757 | 653 | 866 | 729 | 715 | 630 | 796 | 701 | 788 | 664 | 841 | 645 | 740 | 661 | 985 | 750 | 693 | 656 | 993 | 805 | 728 | 672 | 895 | 790 | 806 | 715 | 875 | 778 | 946 | 842 | 1153 | 1299 | 1496 | 1269 | 1455 | 1266 | 1327 | 1204 | 1514 |
| Percentage of Revenues | 8.8 | 9.0 | 9.3 | 9.2 | 9.3 | 9.3 | 9.2 | 8.7 | 8.5 | 9.5 | 8.7 | 8.1 | 8.1 | 8.9 | 8.7 | 8.2 | 8.3 | 9.1 | 8.9 | 8.8 | 9.6 | 11.1 | 9.6 | 10.0 | 10.1 | 11.2 | 10.3 | 10.0 | 10.9 | 13.7 | 13.1 | 11.2 | 10.9 | 14.7 | 12.6 | 12.3 | 12.0 | 18.7 | 19.5 | 17.9 | 18.4 | 22.8 | 28.9 | 28.3 | 28.9 | 32.6 | 30.8 | 30.6 | 29.1 | 32.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 81300.0 | 68100.0 | 81300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 78800.0 | 66400.0 | 0.0 | 0.0 | 37000.0 | 66100.0 | 98500.0 | 0.0 | 0.0 | 0.0 | 99300.0 | 0.0 | 36400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo | 34650.0 | 44450.0 | 0.0 | 27100.0 | 34050.0 | 40650.0 | 0.0 | 77800.0 | 32750.0 | 90000.0 | 0.0 | 37850.0 | 32650.0 | 43300.0 | 0.0 | 35750.0 | 31500.0 | 79600.0 | 0.0 | 39400.0 | 33200.0 | 84100.0 | 0.0 | 74000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 99300.0 | 0.0 | 72800.0 | 0.0 | 0.0 | 0.0 | 80600.0 | 71500.0 | 87500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 1140 | 1244 | 1109 | 1368 | 1016 | 1171 | 1107 | 1380 | 1091 | 1228 | 1117 | 1361 | 1076 | 1251 | 1121 | 1310 | 1074 | 1175 |
| Percentage of Revenues | 14.4 | 12.6 | 13.7 | 15.5 | 13.9 | 13.4 | 13.3 | 15.5 | 14.2 | 13.0 | 12.7 | 14.5 | 13.3 | 12.9 | 13.4 | 14.9 | 14.1 | 13.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 136800.0 | 101600.0 | 117100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC | 28500.0 | 41466.7 | 0.0 | 22800.0 | 33866.7 | 39033.3 | 0.0 | 34500.0 | 36366.7 | 40933.3 | 0.0 | 45366.7 | 35866.7 | 31275.0 | 0.0 | 10916.7 | 8950.0 | 9791.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 523 | 553 | 499 | 611 | 494 | 544 | 513 | 642 | 531 | 575 | 531 | 628 | 523 | 557 | 510 | 604 | 514 | 530 | 491 | 635 | 509 | 551 | 488 | 592 | 504 | 545 |
| Percentage of Revenues | 6.6 | 5.6 | 6.1 | 6.9 | 6.7 | 6.2 | 6.1 | 7.2 | 6.9 | 6.1 | 6.0 | 6.7 | 6.5 | 5.7 | 6.1 | 6.9 | 6.7 | 6.1 | 6.2 | 7.1 | 7.4 | 7.3 | 7.3 | 8.0 | 7.7 | 6.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 61100.0 | 49400.0 | 54400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 63500.0 | 50900.0 | 0.0 | 0.0 | 29600.0 | 50400.0 | 54500.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany | 52300.0 | 55300.0 | 0.0 | 20366.7 | 49400.0 | 54400.0 | 0.0 | 32100.0 | 53100.0 | 28750.0 | 0.0 | 31400.0 | 26150.0 | 27850.0 | 0.0 | 60400.0 | 51400.0 | 53000.0 | 0.0 | 63500.0 | 50900.0 | 55100.0 | 0.0 | 59200.0 | 50400.0 | 54500.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | -95.0 | -96.0 | -93.0 | -91.0 | -98.0 | -92.0 | -98.0 | -92.0 | -98.0 | -106.0 | -109.0 | -104.0 | -109.0 | -113.0 | -2.0 | -3.0 | -5.0 | -4.0 |
| Percentage of Revenues | -1.2 | -1.0 | -1.1 | -1.0 | -1.3 | -1.1 | -1.2 | -1.0 | -1.3 | -1.1 | -1.2 | -1.1 | -1.3 | -1.2 | -0.0 | -0.0 | -0.1 | -0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -9100.0 | -9800.0 | -9200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC us-gaap:IntersegmentElimination | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 98.9 | 0.0 | 98.9 | 99.0 | 100.0 | 0.0 | 99.0 | 100.0 | 100.0 | 0.0 | 75.0 | 100.0 | 80.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 95 | 95 | 93 | 91 | 97 | 93 | 99 | 92 | 97 | 106 | 109 | 103 | 108 | 113 | 15 | 12 | 13 | 12 |
| Percentage of Revenues | 1.2 | 1.0 | 1.1 | 1.0 | 1.3 | 1.1 | 1.2 | 1.0 | 1.3 | 1.1 | 1.2 | 1.1 | 1.3 | 1.2 | 0.2 | 0.1 | 0.2 | 0.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 9100.0 | 9700.0 | 9300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC us-gaap:CorporateNonSegment us-gaap:CorporateAndOther | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 12 | 11 | 8.0 | 5.0 | -26.0 | 2.0 | 0.0 | 1.0 | -2.0 | 2.0 | 0.0 | -1.0 | -1.0 | -2.0 | -1.0 | 0.0 | 3.0 | 6.0 |
| Percentage of Revenues | 0.2 | 0.1 | 0.1 | 0.1 | -0.4 | 0.0 | 0.0 | 0.0 | -0.0 | 0.0 | 0.0 | -0.0 | -0.0 | -0.0 | -0.0 | 0.0 | 0.0 | 0.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 500.0 | -2600.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 307 | 299 | 285 | 415 | 282 | 274 | 274 | 418 | 276 | 271 | 255 | 407 | 266 | 312 | 272 | 370 | 267 | 269 |
| Percentage of Revenues | 3.9 | 3.0 | 3.5 | 4.7 | 3.9 | 3.1 | 3.3 | 4.7 | 3.6 | 2.9 | 2.9 | 4.3 | 3.3 | 3.2 | 3.2 | 4.2 | 3.5 | 3.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 41500.0 | 28200.0 | 27400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:AtlanticCityElectricCompany us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | -6.0 | 18 | 29 | -9.0 | -36.0 | 42 | 4.0 | -1.0 | 10.0 | 16 | 1.0 | -1.0 | -1.0 | -7.0 | 25 | 40 | 35 | 40 |
| Percentage of Revenues | -0.1 | 0.2 | 0.4 | -0.1 | -0.5 | 0.5 | 0.0 | -0.0 | 0.1 | 0.2 | 0.0 | -0.0 | -0.0 | -0.1 | 0.3 | 0.5 | 0.5 | 0.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -900.0 | -3600.0 | 4200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 688 | 956 | 785 | 740 | 652 | 895 | 775 | 704 | 639 | 960 | 799 | 732 | 663 | 984 | 788 | 698 | 639 | 911 |
| Percentage of Revenues | 8.7 | 9.7 | 9.7 | 8.4 | 8.9 | 10.2 | 9.3 | 7.9 | 8.3 | 10.1 | 9.1 | 7.8 | 8.2 | 10.2 | 9.4 | 8.0 | 8.4 | 10.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 74000.0 | 65200.0 | 89500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:BaltimoreGasAndElectricCompany us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 18 | 62 | 12 | -35.0 | -25.0 | 18 | -31.0 | -50.0 | -9.0 | -24.0 | 5.0 | -8.0 | -10.0 | 14 | 2.0 | 24 | 26 | 22 |
| Percentage of Revenues | 0.2 | 0.6 | 0.1 | -0.4 | -0.3 | 0.2 | -0.4 | -0.6 | -0.1 | -0.3 | 0.1 | -0.1 | -0.1 | 0.1 | 0.0 | 0.3 | 0.3 | 0.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -3500.0 | -2500.0 | 1800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 1499 | 1473 | 1393 | 1678 | 1442 | 1421 | 1436 | 1633 | 1360 | 1432 | 1369 | 1606 | 1408 | 1498 | 1307 | 1547 | 1331 | 1276 |
| Percentage of Revenues | 18.9 | 14.9 | 17.2 | 19.0 | 19.7 | 16.2 | 17.2 | 18.3 | 17.7 | 15.1 | 15.5 | 17.1 | 17.4 | 15.5 | 15.6 | 17.6 | 17.5 | 14.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 167800.0 | 144200.0 | 142100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:CommonwealthEdisonCo us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 10.0 | 9.0 | 8.0 | 8.0 | -25.0 | 2.0 | -5.0 | -6.0 | 1.0 | 2.0 | 0.0 | 1.0 | 6.0 | 1.0 | -2.0 | 0.0 | 1.0 | 10.0 |
| Percentage of Revenues | 0.1 | 0.1 | 0.1 | 0.1 | -0.3 | 0.0 | -0.1 | -0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.1 | 0.0 | -0.0 | 0.0 | 0.0 | 0.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 800.0 | -2500.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 288 | 373 | 309 | 329 | 292 | 348 | 324 | 325 | 286 | 378 | 331 | 327 | 283 | 383 | 331 | 327 | 281 | 352 |
| Percentage of Revenues | 3.6 | 3.8 | 3.8 | 3.7 | 4.0 | 4.0 | 3.9 | 3.6 | 3.7 | 4.0 | 3.8 | 3.5 | 3.5 | 4.0 | 3.9 | 3.7 | 3.7 | 4.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 32900.0 | 29200.0 | 34800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:DelmarvaPowerandLightCompany us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 7.0 | 10.0 | 6.0 | 5.0 | 3.0 | 6.0 | -2.0 | -7.0 | 3.0 | -2.0 | -6.0 | 4.0 | 7.0 | 2.0 | 3.0 | 3.0 | 3.0 | 3.0 |
| Percentage of Revenues | 0.1 | 0.1 | 0.1 | 0.1 | 0.0 | 0.1 | -0.0 | -0.1 | 0.0 | -0.0 | -0.1 | 0.0 | 0.1 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 500.0 | 300.0 | 600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 686 | 879 | 746 | 808 | 678 | 807 | 769 | 785 | 652 | 902 | 769 | 753 | 646 | 864 | 726 | 712 | 627 | 793 |
| Percentage of Revenues | 8.7 | 8.9 | 9.2 | 9.1 | 9.3 | 9.2 | 9.2 | 8.8 | 8.5 | 9.5 | 8.7 | 8.0 | 8.0 | 8.9 | 8.7 | 8.1 | 8.2 | 9.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 80800.0 | 67800.0 | 80700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PecoEnergyCo us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 42 | 46 | 36 | 31 | -64.0 | 21 | -15.0 | -6.0 | 0.0 | 20 | -4.0 | -2.0 | -3.0 | 19 | 14 | 16 | 22 | 43 |
| Percentage of Revenues | 0.5 | 0.5 | 0.4 | 0.4 | -0.9 | 0.2 | -0.2 | -0.1 | 0.0 | 0.2 | -0.0 | -0.0 | -0.0 | 0.2 | 0.2 | 0.2 | 0.3 | 0.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 3100.0 | -6400.0 | 2100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 145.5 | 200.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 1098 | 1198 | 1073 | 1337 | 1080 | 1150 | 1121 | 1386 | 1091 | 1208 | 1121 | 1363 | 1079 | 1232 | 1108 | 1294 | 1052 | 1132 |
| Percentage of Revenues | 13.9 | 12.1 | 13.2 | 15.1 | 14.8 | 13.1 | 13.4 | 15.5 | 14.2 | 12.7 | 12.7 | 14.5 | 13.4 | 12.7 | 13.2 | 14.8 | 13.8 | 12.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 133700.0 | 108000.0 | 115000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PepcoHoldingsLLC us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 20 | 26 | 20 | 18 | -13.0 | 16 | -11.0 | -1.0 | 1.0 | 16 | -4.0 | -2.0 | -8.0 | 20 | 3.0 | 5.0 | 7.0 | 16 |
| Percentage of Revenues | 0.3 | 0.3 | 0.2 | 0.2 | -0.2 | 0.2 | -0.1 | -0.0 | 0.0 | 0.2 | -0.0 | -0.0 | -0.1 | 0.2 | 0.0 | 0.1 | 0.1 | 0.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 1800.0 | -1300.0 | 1600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany exc:OtherRegulatedRevenue | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 503 | 527 | 479 | 593 | 507 | 528 | 523 | 643 | 530 | 559 | 535 | 630 | 531 | 537 | 506 | 599 | 507 | 514 |
| Percentage of Revenues | 6.4 | 5.3 | 5.9 | 6.7 | 6.9 | 6.0 | 6.3 | 7.2 | 6.9 | 5.9 | 6.1 | 6.7 | 6.6 | 5.5 | 6.0 | 6.8 | 6.7 | 5.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 59300.0 | 50700.0 | 52800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:PotomacElectricPowerCompany us-gaap:RegulatedOperation | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | -794.0 | -802.0 | -892.0 | -845.0 | -760.0 | -826.0 | -870.0 | -763.0 | -751.0 | -786.0 | -858.0 | -780.0 | -779.0 | -876.0 | -758.0 | -762.0 | -735.0 | -770.0 | -3164.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Revenues | -10.0 | -8.1 | -11.0 | -9.5 | -10.4 | -9.4 | -10.4 | -8.5 | -9.8 | -8.3 | -9.7 | -8.3 | -9.6 | -9.0 | -9.0 | -8.7 | -9.6 | -8.8 | -40.2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -84500.0 | -76000.0 | -82600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:IntersegmentElimination | 100.0 | 100.4 | 0.0 | 100.0 | 100.0 | 100.2 | 0.0 | 99.9 | 100.1 | 100.1 | 0.0 | 100.1 | 100.4 | 100.0 | 0.0 | 100.4 | 100.1 | 0.0 | 0.0 | -0.0 | -0.0 | -0.0 | 0.0 | -0.0 | -0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 107 | 89 | 87 | 85 | 86 | 99 | 97 | 112 | 108 | 120 | 125 | 130 | 125 | 134 | 156 | 207 | 179 | 206 |
| Percentage of Revenues | 1.4 | 0.9 | 1.1 | 1.0 | 1.2 | 1.1 | 1.2 | 1.3 | 1.4 | 1.3 | 1.4 | 1.4 | 1.5 | 1.4 | 1.9 | 2.4 | 2.3 | 2.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 8500.0 | 8600.0 | 9900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:CorporateNonSegment exc:ContractswithCustomers exc:GenerationAllOtherSegments | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | -208.0 | -43.0 | -104.0 | 50 | 27 | 210 | -42.0 | 83 | 51 | -40.0 | -156.0 | 10.0 | 26 | -86.0 | -85.0 | 42 | -152.0 | 44 |
| Percentage of Revenues | -2.6 | -0.4 | -1.3 | 0.6 | 0.4 | 2.4 | -0.5 | 0.9 | 0.7 | -0.4 | -1.8 | 0.1 | 0.3 | -0.9 | -1.0 | 0.5 | -2.0 | 0.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 5000.0 | 2700.0 | 21000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:CorporateNonSegment exc:Other exc:GenerationAllOtherSegments | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 179 | 353 | 156 | 249 | 175 | 155 | 174 | 288 | 178 | 130 | 102 | 156 | 165 | 149 | 121 | 164 | 186 | 168 |
| Percentage of Revenues | 2.3 | 3.6 | 1.9 | 2.8 | 2.4 | 1.8 | 2.1 | 3.2 | 2.3 | 1.4 | 1.2 | 1.7 | 2.0 | 1.5 | 1.4 | 1.9 | 2.4 | 1.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 24900.0 | 17500.0 | 15500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationErcot | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 1062 | 1174 | 1093 | 1327 | 1100 | 1264 | 1255 | 1351 | 1162 | 1286 | 1270 | 1397 | 1220 | 1355 | 1263 | 1397 | 1368 | 1494 |
| Percentage of Revenues | 13.4 | 11.9 | 13.5 | 15.0 | 15.0 | 14.5 | 15.0 | 15.1 | 15.1 | 13.6 | 14.4 | 14.9 | 15.1 | 14.0 | 15.1 | 15.9 | 17.9 | 17.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 132700.0 | 110000.0 | 126400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationMidAtlantic | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 975 | 1009 | 944 | 974 | 855 | 944 | 1012 | 1052 | 974 | 1055 | 1095 | 1095 | 1062 | 1273 | 975 | 982 | 986 | 980 |
| Percentage of Revenues | 12.3 | 10.2 | 11.6 | 11.0 | 11.7 | 10.8 | 12.1 | 11.8 | 12.7 | 11.1 | 12.4 | 11.6 | 13.2 | 13.1 | 11.6 | 11.2 | 12.9 | 11.2 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 97400.0 | 85500.0 | 94400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationMidwest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 253 | 864 | 402 | 169 | 209 | 503 | 405 | 160 | 177 | 584 | 508 | 200 | 295 | 522 | 421 | 226 | 244 | 768 |
| Percentage of Revenues | 3.2 | 8.7 | 5.0 | 1.9 | 2.9 | 5.8 | 4.9 | 1.8 | 2.3 | 6.2 | 5.8 | 2.1 | 3.7 | 5.4 | 5.0 | 2.6 | 3.2 | 8.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 16900.0 | 20900.0 | 50300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationNaturalGas | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 376 | 382 | 370 | 401 | 336 | 335 | 376 | 414 | 373 | 409 | 418 | 475 | 392 | 439 | 444 | 454 | 405 | 303 |
| Percentage of Revenues | 4.8 | 3.9 | 4.6 | 4.5 | 4.6 | 3.8 | 4.5 | 4.6 | 4.9 | 4.3 | 4.7 | 5.1 | 4.9 | 4.5 | 5.3 | 5.2 | 5.3 | 3.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 40100.0 | 33600.0 | 33500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationNewYork | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 921 | 1172 | 868 | 937 | 776 | 1007 | 838 | 873 | 814 | 1165 | 157 | 293 | 210 | 210 | 155 | 167 | 142 | 128 |
| Percentage of Revenues | 11.6 | 11.9 | 10.7 | 10.6 | 10.6 | 11.5 | 10.0 | 9.8 | 10.6 | 12.3 | 1.8 | 3.1 | 2.6 | 2.2 | 1.8 | 1.9 | 1.9 | 1.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 93700.0 | 77600.0 | 100700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationOtherRegions | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 3513 | 4090 | 3431 | 3888 | 3242 | 3705 | 3655 | 3978 | 3501 | 4045 | 3759 | 4082 | 3600 | 4151 | 3467 | 3668 | 3549 | 3662 |
| Percentage of Revenues | 44.4 | 41.4 | 42.3 | 43.9 | 44.3 | 42.4 | 43.8 | 44.6 | 45.5 | 42.7 | 42.6 | 43.4 | 44.6 | 42.8 | 41.4 | 41.8 | 46.6 | 41.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 388800.0 | 324200.0 | 370500.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationReportableSegmentsTotal | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 3873 | 5043 | 3920 | 4142 | 3537 | 4307 | 4157 | 4250 | 3786 | 4749 | 4392 | 4412 | 4020 | 4807 | 4044 | 4101 | 3972 | 4636 |
| Percentage of Revenues | 48.9 | 51.0 | 48.3 | 46.8 | 48.3 | 49.2 | 49.8 | 47.6 | 49.2 | 50.1 | 49.8 | 46.9 | 49.8 | 49.6 | 48.3 | 46.8 | 52.1 | 52.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 414200.0 | 353700.0 | 430700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ContractswithCustomers exc:GenerationTotalConsolidatedGroup | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 92 | -101.0 | 43 | 74 | 52 | 28 | 31 | 72 | 47 | 79 | 101 | 289 | 111 | 59 | 88 | 144 | 61 | 24 |
| Percentage of Revenues | 1.2 | -1.0 | 0.5 | 0.8 | 0.7 | 0.3 | 0.4 | 0.8 | 0.6 | 0.8 | 1.1 | 3.1 | 1.4 | 0.6 | 1.0 | 1.6 | 0.8 | 0.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 7400.0 | 5200.0 | 2800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationErcot | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 24 | -14.0 | -16.0 | -20.0 | -35.0 | -96.0 | 8.0 | 10.0 | 21 | -24.0 | 42 | 52 | 58 | 80 | 45 | 24 | -12.0 | -65.0 |
| Percentage of Revenues | 0.3 | -0.1 | -0.2 | -0.2 | -0.5 | -1.1 | 0.1 | 0.1 | 0.3 | -0.3 | 0.5 | 0.6 | 0.7 | 0.8 | 0.5 | 0.3 | -0.2 | -0.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | -2000.0 | -3500.0 | -9600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationMidAtlantic | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | -13.0 | -11.0 | 72 | 68 | 107 | 64 | 60 | 47 | 68 | 59 | 21 | 26 | 73 | 71 | 73 | 67 | 72 | 71 |
| Percentage of Revenues | -0.2 | -0.1 | 0.9 | 0.8 | 1.5 | 0.7 | 0.7 | 0.5 | 0.9 | 0.6 | 0.2 | 0.3 | 0.9 | 0.7 | 0.9 | 0.8 | 0.9 | 0.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 6800.0 | 10700.0 | 6400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationMidwest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 254 | 462 | 253 | 154 | 144 | 169 | 264 | 105 | 156 | 295 | 371 | 197 | 194 | 433 | 347 | 234 | 186 | 150 |
| Percentage of Revenues | 3.2 | 4.7 | 3.1 | 1.7 | 2.0 | 1.9 | 3.2 | 1.2 | 2.0 | 3.1 | 4.2 | 2.1 | 2.4 | 4.5 | 4.1 | 2.7 | 2.4 | 1.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 15400.0 | 14400.0 | 16900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationNaturalGas | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 5.0 | -45.0 | 0.0 | 5.0 | 5.0 | -21.0 | 9.0 | 15 | 17 | -16.0 | 1.0 | -6.0 | -2.0 | -29.0 | -1.0 | -21.0 | -13.0 | -3.0 |
| Percentage of Revenues | 0.1 | -0.5 | 0.0 | 0.1 | 0.1 | -0.2 | 0.1 | 0.2 | 0.2 | -0.2 | 0.0 | -0.1 | -0.0 | -0.3 | -0.0 | -0.2 | -0.2 | -0.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 500.0 | 500.0 | -2100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationNewYork | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 126 | 268 | 163 | 186 | 43 | 72 | 157 | 192 | 64 | 194 | 199 | 265 | 113 | 109 | 114 | 181 | 126 | 61 |
| Percentage of Revenues | 1.6 | 2.7 | 2.0 | 2.1 | 0.6 | 0.8 | 1.9 | 2.2 | 0.8 | 2.0 | 2.3 | 2.8 | 1.4 | 1.1 | 1.4 | 2.1 | 1.7 | 0.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 18600.0 | 4300.0 | 7200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationOtherRegions | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 234 | 97 | 262 | 313 | 172 | 47 | 265 | 336 | 217 | 292 | 462 | 659 | 339 | 358 | 351 | 373 | 210 | 48 |
| Percentage of Revenues | 3.0 | 1.0 | 3.2 | 3.5 | 2.3 | 0.5 | 3.2 | 3.8 | 2.8 | 3.1 | 5.2 | 7.0 | 4.2 | 3.7 | 4.2 | 4.3 | 2.8 | 0.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 31300.0 | 17200.0 | 4700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationReportableSegmentsTotal | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 280 | 516 | 411 | 517 | 343 | 426 | 487 | 524 | 424 | 547 | 677 | 866 | 559 | 705 | 613 | 649 | 244 | 242 |
| Percentage of Revenues | 3.5 | 5.2 | 5.1 | 5.8 | 4.7 | 4.9 | 5.8 | 5.9 | 5.5 | 5.8 | 7.7 | 9.2 | 6.9 | 7.3 | 7.3 | 7.4 | 3.2 | 2.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 51700.0 | 34300.0 | 42600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:Other exc:GenerationTotalConsolidatedGroup | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 |
| Value | -101.0 | 46 | -17.0 | 135 | 113 | 309 | 55 | 195 | 159 | 80 | -31.0 | 140 | 151 | 48 | 839 | 709 | 455 | 1168 | 675 | 713 | -66.0 | 1044 | 710 | 469 | 569 |
| Percentage of Revenues | -1.3 | 0.5 | -0.2 | 1.5 | 1.5 | 3.5 | 0.7 | 2.2 | 2.1 | 0.8 | -0.4 | 1.5 | 1.9 | 0.5 | 10.0 | 8.1 | 6.0 | 13.3 | 8.6 | 7.9 | -1.0 | 13.8 | 10.6 | 6.3 | 8.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 13500.0 | 11300.0 | 30900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 71300.0 | -6600.0 | 0.0 | 0.0 | 23450.0 | 56900.0 |
| Percentage of RevenueFromRelatedParties us-gaap:CorporateNonSegment exc:GenerationAllOtherSegments | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 524 | 491 | 595 | 484 | 472 | 480 | 511 | 474 | 484 | 455 | 550 | 458 | 487 | 451 | 515 | 446 | 449 | 419 |
| Percentage of Revenues | 6.6 | 5.0 | 7.3 | 5.5 | 6.4 | 5.5 | 6.1 | 5.3 | 6.3 | 4.8 | 6.2 | 4.9 | 6.0 | 4.7 | 6.1 | 5.1 | 5.9 | 4.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 48400.0 | 47200.0 | 48000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:CorporateNonSegment us-gaap:CorporateAndOther | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 319 | 310 | 293 | 420 | 256 | 276 | 274 | 419 | 274 | 273 | 255 | 406 | 265 | 310 | 271 | 370 | 270 | 275 |
| Percentage of Revenues | 4.0 | 3.1 | 3.6 | 4.7 | 3.5 | 3.2 | 3.3 | 4.7 | 3.6 | 2.9 | 2.9 | 4.3 | 3.3 | 3.2 | 3.2 | 4.2 | 3.5 | 3.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 42000.0 | 25600.0 | 27600.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:AtlanticCityElectricCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 682 | 974 | 814 | 731 | 616 | 937 | 779 | 703 | 649 | 976 | 800 | 731 | 662 | 977 | 813 | 738 | 674 | 951 | 725 | 628 | 1036 | 761 | 697 | 653 | 1054 |
| Percentage of Revenues | 8.6 | 9.8 | 10.0 | 8.3 | 8.4 | 10.7 | 9.3 | 7.9 | 8.4 | 10.3 | 9.1 | 7.8 | 8.2 | 10.1 | 9.7 | 8.4 | 8.8 | 10.9 | 9.8 | 9.6 | 11.7 | 10.5 | 10.1 | 10.8 | 14.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 73100.0 | 61600.0 | 93700.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 36250.0 | 62800.0 | 103600.0 | 0.0 | 0.0 | 0.0 | 105400.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:BaltimoreGasAndElectricCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 24166.7 | 62800.0 | 14800.0 | 0.0 | 23233.3 | 32650.0 | 6587.5 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 1517 | 1535 | 1405 | 1643 | 1417 | 1439 | 1405 | 1583 | 1351 | 1408 | 1374 | 1598 | 1398 | 1512 | 1309 | 1571 | 1357 | 1298 | 1376 | 1148 | 1185 | 1080 | 1222 | 1128 | 1134 |
| Percentage of Revenues | 19.2 | 15.5 | 17.3 | 18.6 | 19.4 | 16.5 | 16.8 | 17.7 | 17.6 | 14.9 | 15.6 | 17.0 | 17.3 | 15.6 | 15.6 | 17.9 | 17.8 | 14.8 | 18.6 | 17.6 | 13.4 | 14.9 | 17.7 | 18.7 | 15.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 164300.0 | 141700.0 | 143900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 68800.0 | 114800.0 | 118500.0 | 0.0 | 0.0 | 0.0 | 113400.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:CommonwealthEdisonCo | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 137600.0 | 114800.0 | 118500.0 | 0.0 | 122200.0 | 0.0 | 113400.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 298 | 382 | 317 | 337 | 267 | 350 | 319 | 319 | 287 | 380 | 331 | 328 | 289 | 384 | 329 | 327 | 282 | 362 |
| Percentage of Revenues | 3.8 | 3.9 | 3.9 | 3.8 | 3.6 | 4.0 | 3.8 | 3.6 | 3.7 | 4.0 | 3.8 | 3.5 | 3.6 | 4.0 | 3.9 | 3.7 | 3.7 | 4.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 33700.0 | 26700.0 | 35000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:DelmarvaPowerandLightCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 4153 | 5559 | 4331 | 4659 | 3880 | 4733 | 4644 | 4774 | 4210 | 5296 | 5069 | 5278 | 4579 | 5512 | 4657 | 4750 | 4216 | 4878 | 4768 | 4232 | 5840 | 4802 | 4412 | 3789 | 4390 |
| Percentage of Revenues | 52.5 | 56.2 | 53.4 | 52.6 | 53.0 | 54.1 | 55.7 | 53.5 | 54.8 | 55.9 | 57.5 | 56.1 | 56.7 | 56.9 | 55.6 | 54.2 | 55.3 | 55.7 | 64.4 | 65.0 | 66.1 | 66.2 | 63.8 | 62.9 | 60.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 465900.0 | 388000.0 | 473300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 238400.0 | 423200.0 | 584000.0 | 0.0 | 0.0 | 0.0 | 439000.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:ExelonGenerationCoLLC | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 2325.9 | 2784.2 | 2781.0 | 0.0 | 3939.3 | 1885.1 | 1389.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 271 | 252 | 199 | 323 | 227 | 183 | 205 | 360 | 225 | 209 | 203 | 445 | 276 | 208 | 209 | 308 | 247 | 192 | 172 | 289 | 207 | 163 | 172 | 317 | 194 | 182 | 195 | 303 | 198 | 243 |
| Percentage of Revenues | 3.4 | 2.5 | 2.5 | 3.6 | 3.1 | 2.1 | 2.5 | 4.0 | 2.9 | 2.2 | 2.3 | 4.7 | 3.4 | 2.1 | 2.5 | 3.5 | 3.2 | 2.2 | 2.2 | 3.2 | 3.0 | 2.2 | 2.6 | 4.3 | 3.0 | 2.1 | 2.7 | 4.4 | 3.3 | 3.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 32300.0 | 22700.0 | 18300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 28900.0 | 20700.0 | 0.0 | 0.0 | 15850.0 | 19400.0 | 18200.0 | 0.0 | 0.0 | 0.0 | 24300.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationErcot | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 1086 | 1160 | 1077 | 1307 | 1065 | 1168 | 1263 | 1361 | 1183 | 1262 | 1312 | 1449 | 1278 | 1435 | 1308 | 1421 | 1356 | 1429 | 1436 | 1813 | 1432 | 1532 | 1499 | 1622 | 1336 | 1517 | 1267 | 1285 | 1272 | 1441 |
| Percentage of Revenues | 13.7 | 11.7 | 13.3 | 14.8 | 14.5 | 13.4 | 15.1 | 15.2 | 15.4 | 13.3 | 14.9 | 15.4 | 15.8 | 14.8 | 15.6 | 16.2 | 17.8 | 16.3 | 18.2 | 20.1 | 20.7 | 20.2 | 22.4 | 21.9 | 20.5 | 17.2 | 17.5 | 18.6 | 21.1 | 19.9 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 130700.0 | 106500.0 | 116800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 181300.0 | 143200.0 | 0.0 | 0.0 | 81100.0 | 133600.0 | 151700.0 | 0.0 | 0.0 | 0.0 | 144100.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationMidAtlantic | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 962 | 998 | 1016 | 1042 | 962 | 1008 | 1072 | 1099 | 1042 | 1114 | 1116 | 1121 | 1135 | 1344 | 1048 | 1049 | 1058 | 1051 | 1072 | 1163 | 1076 | 1089 | 1082 | 1150 | 1205 | 1275 | 1165 | 1062 | 981 | 1258 |
| Percentage of Revenues | 12.2 | 10.1 | 12.5 | 11.8 | 13.1 | 11.5 | 12.8 | 12.3 | 13.6 | 11.8 | 12.7 | 11.9 | 14.1 | 13.9 | 12.5 | 12.0 | 13.9 | 12.0 | 13.6 | 12.9 | 15.6 | 14.4 | 16.1 | 15.5 | 18.5 | 14.4 | 16.1 | 15.4 | 16.3 | 17.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 104200.0 | 96200.0 | 100800.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 116300.0 | 107600.0 | 0.0 | 0.0 | 57500.0 | 120500.0 | 127500.0 | 0.0 | 0.0 | 0.0 | 125800.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationMidwest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 507 | 1326 | 655 | 323 | 353 | 672 | 669 | 265 | 333 | 879 | 879 | 397 | 489 | 955 | 768 | 460 | 430 | 918 |
| Percentage of Revenues | 6.4 | 13.4 | 8.1 | 3.6 | 4.8 | 7.7 | 8.0 | 3.0 | 4.3 | 9.3 | 10.0 | 4.2 | 6.1 | 9.9 | 9.2 | 5.2 | 5.6 | 10.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 32300.0 | 35300.0 | 67200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationNaturalGas | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 381 | 337 | 370 | 406 | 341 | 314 | 385 | 429 | 390 | 393 | 419 | 469 | 390 | 410 | 440 | 434 | 352 | 310 | 292 | 331 | 356 | 218 | 210 | 254 | 222 | 310 | 229 | 230 | 194 | 190 |
| Percentage of Revenues | 4.8 | 3.4 | 4.6 | 4.6 | 4.7 | 3.6 | 4.6 | 4.8 | 5.1 | 4.1 | 4.8 | 5.0 | 4.8 | 4.2 | 5.2 | 4.9 | 4.6 | 3.5 | 3.7 | 3.7 | 5.2 | 2.9 | 3.1 | 3.4 | 3.4 | 3.5 | 3.2 | 3.3 | 3.2 | 2.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 40600.0 | 34100.0 | 31400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 33100.0 | 35600.0 | 0.0 | 0.0 | 12700.0 | 22200.0 | 31000.0 | 0.0 | 0.0 | 0.0 | 19000.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationNewYork | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 1047 | 1440 | 1031 | 1123 | 819 | 1079 | 995 | 1065 | 878 | 1359 | 356 | 558 | 323 | 319 | 269 | 348 | 268 | 189 | 241 | 271 | 232 | 222 | 291 | 383 | 294 | 212 | 292 | 381 | 314 | 334 |
| Percentage of Revenues | 13.2 | 14.6 | 12.7 | 12.7 | 11.2 | 12.3 | 11.9 | 11.9 | 11.4 | 14.3 | 4.0 | 5.9 | 4.0 | 3.3 | 3.2 | 4.0 | 3.5 | 2.2 | 3.1 | 3.0 | 3.4 | 2.9 | 4.3 | 5.2 | 4.5 | 2.4 | 4.0 | 5.5 | 5.2 | 4.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 112300.0 | 81900.0 | 107900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 27100.0 | 23200.0 | 0.0 | 0.0 | 19150.0 | 29400.0 | 21200.0 | 0.0 | 0.0 | 0.0 | 33400.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationOtherRegions | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 3747 | 4187 | 3693 | 4201 | 3414 | 3752 | 3920 | 4314 | 3718 | 4337 | 4221 | 4741 | 3939 | 4509 | 3815 | 4042 | 3719 | 3720 | 3713 | 4322 | 3655 | 3695 | 3728 | 4245 | 3617 | 4354 | 3537 | 3533 | 3170 | 4011 |
| Percentage of Revenues | 47.3 | 42.3 | 45.5 | 47.5 | 46.6 | 42.9 | 47.0 | 48.3 | 48.4 | 45.8 | 47.9 | 50.4 | 48.8 | 46.5 | 45.5 | 46.1 | 48.8 | 42.5 | 47.1 | 48.0 | 52.9 | 48.8 | 55.6 | 57.4 | 55.5 | 49.3 | 48.8 | 51.1 | 52.6 | 55.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 420100.0 | 341400.0 | 375200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 432200.0 | 365500.0 | 0.0 | 0.0 | 212250.0 | 361700.0 | 435400.0 | 0.0 | 0.0 | 0.0 | 401100.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationReportableSegmentsTotal | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 |
| Value | 4153 | 5559 | 4331 | 4659 | 3880 | 4733 | 4644 | 4774 | 4210 | 5296 | 5069 | 5278 | 4579 | 5512 | 4654 | 4751 | 4174 | 4888 | 4388 | 5035 | 3589 | 4739 | 4294 | 4768 | 4232 | 5840 |
| Percentage of Revenues | 52.5 | 56.2 | 53.4 | 52.6 | 53.0 | 54.1 | 55.7 | 53.5 | 54.8 | 55.9 | 57.5 | 56.1 | 56.7 | 56.9 | 55.5 | 54.2 | 54.8 | 55.8 | 55.7 | 55.9 | 51.9 | 62.6 | 64.1 | 64.4 | 65.0 | 66.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 465900.0 | 388000.0 | 473300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 503500.0 | 358900.0 | 0.0 | 0.0 | 238400.0 | 423200.0 | 584000.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:GenerationTotalConsolidatedGroup | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 |
| Value | 693 | 889 | 752 | 813 | 681 | 813 | 767 | 778 | 655 | 900 | 763 | 757 | 653 | 866 | 729 | 715 | 630 | 796 | 740 | 661 | 985 | 751 | 693 | 656 | 993 |
| Percentage of Revenues | 8.8 | 9.0 | 9.3 | 9.2 | 9.3 | 9.3 | 9.2 | 8.7 | 8.5 | 9.5 | 8.7 | 8.1 | 8.1 | 8.9 | 8.7 | 8.2 | 8.3 | 9.1 | 10.0 | 10.1 | 11.2 | 10.4 | 10.0 | 10.9 | 13.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 81300.0 | 68100.0 | 81300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 37000.0 | 66100.0 | 98500.0 | 0.0 | 0.0 | 0.0 | 99300.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PecoEnergyCo | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 74000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 99300.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 1140 | 1244 | 1109 | 1368 | 1016 | 1171 | 1106 | 1380 | 1091 | 1228 | 1117 | 1361 | 1076 | 1251 | 1122 | 1310 | 1074 | 1175 |
| Percentage of Revenues | 14.4 | 12.6 | 13.7 | 15.5 | 13.9 | 13.4 | 13.3 | 15.5 | 14.2 | 13.0 | 12.7 | 14.5 | 13.3 | 12.9 | 13.4 | 14.9 | 14.1 | 13.4 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 136800.0 | 101600.0 | 117100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PepcoHoldingsLLC | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 523 | 553 | 499 | 611 | 494 | 544 | 512 | 642 | 531 | 575 | 531 | 628 | 523 | 557 | 509 | 604 | 514 | 530 |
| Percentage of Revenues | 6.6 | 5.6 | 6.1 | 6.9 | 6.7 | 6.2 | 6.1 | 7.2 | 6.9 | 6.1 | 6.0 | 6.7 | 6.5 | 5.7 | 6.1 | 6.9 | 6.7 | 6.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 61100.0 | 49400.0 | 54400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties us-gaap:OperatingSegments exc:PotomacElectricPowerCompany | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-03-31 |
| Value | -101.0 | 46 | -17.0 | 135 | 113 | 309 | 56 | 195 | 159 | 80 | -30.0 | 140 | 151 | 48 | 839 | 723 | 473 | 1181 | 703 | 764 | -37.0 | 1065 | 743 | 523 | 614 | 1488 | 1266 | 881 | 620 | 382 | 608 | 629 | 852 | -21.0 | 559 | -24.0 | 219 |
| Percentage of Revenues | -1.3 | 0.5 | -0.2 | 1.5 | 1.5 | 3.5 | 0.7 | 2.2 | 2.1 | 0.8 | -0.3 | 1.5 | 1.9 | 0.5 | 10.0 | 8.2 | 6.2 | 13.5 | 8.9 | 8.5 | -0.5 | 14.1 | 11.1 | 7.1 | 9.4 | 16.9 | 17.5 | 12.7 | 10.3 | 5.3 | 9.9 | 9.7 | 13.9 | -0.3 | 8.9 | -0.4 | 4.7 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 13500.0 | 11300.0 | 30900.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 76400.0 | -3700.0 | 0.0 | 0.0 | 26150.0 | 61400.0 | 148800.0 | 0.0 | 0.0 | 0.0 | 38200.0 | 0.0 | 31450.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationAllOtherSegments | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 |
| Value | 275 | 257 | 204 | 330 | 234 | 190 | 208 | 365 | 229 | 212 | 203 | 444 | 277 | 209 | 209 | 314 | 247 | 191 | 172 | 295 | 207 | 163 | 170 | 316 | 192 | 180 | 194 | 302 | 197 | 243 | 182 | 427 | 315 | 293 | 291 | 533 |
| Percentage of Revenues | 3.5 | 2.6 | 2.5 | 3.7 | 3.2 | 2.2 | 2.5 | 4.1 | 3.0 | 2.2 | 2.3 | 4.7 | 3.4 | 2.2 | 2.5 | 3.6 | 3.2 | 2.2 | 2.2 | 3.3 | 3.0 | 2.2 | 2.5 | 4.3 | 2.9 | 2.0 | 2.7 | 4.4 | 3.3 | 3.4 | 3.0 | 6.6 | 5.1 | 4.8 | 4.6 | 8.1 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 33000.0 | 23400.0 | 19000.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 29500.0 | 20700.0 | 0.0 | 0.0 | 15800.0 | 19200.0 | 18000.0 | 0.0 | 0.0 | 0.0 | 24300.0 | 0.0 | 21350.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationErcot | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 |
| Value | 1091 | 1165 | 1084 | 1313 | 1074 | 1174 | 1265 | 1364 | 1189 | 1256 | 1308 | 1456 | 1282 | 1440 | 1318 | 1432 | 1365 | 1425 | 1443 | 1800 | 1416 | 1520 | 1409 | 1632 | 1346 | 1513 | 1275 | 1289 | 1277 | 1418 | 1261 | 1391 | 1229 | 1323 | 1293 | 1417 |
| Percentage of Revenues | 13.8 | 11.8 | 13.4 | 14.8 | 14.7 | 13.4 | 15.2 | 15.3 | 15.5 | 13.3 | 14.8 | 15.5 | 15.9 | 14.9 | 15.7 | 16.3 | 17.9 | 16.3 | 18.3 | 20.0 | 20.5 | 20.1 | 21.0 | 22.1 | 20.7 | 17.1 | 17.6 | 18.6 | 21.2 | 19.6 | 20.5 | 21.4 | 20.0 | 21.8 | 20.6 | 21.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 131300.0 | 107400.0 | 117400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 180000.0 | 141600.0 | 0.0 | 0.0 | 81600.0 | 134600.0 | 151300.0 | 0.0 | 0.0 | 0.0 | 141800.0 | 0.0 | 69550.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationMidAtlantic | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 |
| Value | 962 | 998 | 1017 | 1043 | 962 | 1002 | 1069 | 1082 | 1034 | 1108 | 1113 | 1117 | 1130 | 1346 | 1040 | 1038 | 1050 | 1053 | 1069 | 1164 | 1083 | 1095 | 1077 | 1151 | 1206 | 1276 | 1162 | 1061 | 981 | 1270 | 999 | 1013 | 1071 | 1188 | 1205 | 1200 |
| Percentage of Revenues | 12.2 | 10.1 | 12.5 | 11.8 | 13.1 | 11.5 | 12.8 | 12.1 | 13.4 | 11.7 | 12.6 | 11.9 | 14.0 | 13.9 | 12.4 | 11.8 | 13.8 | 12.0 | 13.6 | 12.9 | 15.7 | 14.5 | 16.1 | 15.6 | 18.5 | 14.5 | 16.0 | 15.4 | 16.3 | 17.5 | 16.2 | 15.6 | 17.4 | 19.5 | 19.2 | 18.3 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 104300.0 | 96200.0 | 100200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 116400.0 | 108300.0 | 0.0 | 0.0 | 57550.0 | 120600.0 | 127600.0 | 0.0 | 0.0 | 0.0 | 127000.0 | 0.0 | 50650.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationMidwest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 507 | 1326 | 655 | 323 | 353 | 672 | 669 | 299 | 348 | 894 | 836 | 440 | 526 | 980 | 769 | 480 | 449 | 930 |
| Percentage of Revenues | 6.4 | 13.4 | 8.1 | 3.6 | 4.8 | 7.7 | 8.0 | 3.3 | 4.5 | 9.4 | 9.5 | 4.7 | 6.5 | 10.1 | 9.2 | 5.5 | 5.9 | 10.6 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 32300.0 | 35300.0 | 67200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationNaturalGas | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 |
| Value | 381 | 337 | 370 | 406 | 340 | 314 | 385 | 429 | 390 | 393 | 418 | 469 | 392 | 409 | 437 | 428 | 347 | 307 | 283 | 323 | 346 | 203 | 207 | 250 | 218 | 310 | 230 | 232 | 194 | 187 | 187 | 184 | 174 | 169 | 210 | 185 |
| Percentage of Revenues | 4.8 | 3.4 | 4.6 | 4.6 | 4.6 | 3.6 | 4.6 | 4.8 | 5.1 | 4.1 | 4.7 | 5.0 | 4.9 | 4.2 | 5.2 | 4.9 | 4.6 | 3.5 | 3.6 | 3.6 | 5.0 | 2.7 | 3.1 | 3.4 | 3.3 | 3.5 | 3.2 | 3.4 | 3.2 | 2.6 | 3.0 | 2.8 | 2.8 | 2.8 | 3.3 | 2.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 40600.0 | 34000.0 | 31400.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 32300.0 | 34600.0 | 0.0 | 0.0 | 12500.0 | 21800.0 | 31000.0 | 0.0 | 0.0 | 0.0 | 18700.0 | 0.0 | 9200.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationNewYork | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 |
| Value | 1038 | 1430 | 1018 | 1109 | 804 | 1072 | 992 | 1040 | 861 | 1353 | 406 | 513 | 287 | 288 | 270 | 335 | 259 | 184 | 221 | 238 | 223 | 223 | 222 | 376 | 289 | 214 | 286 | 375 | 308 | 341 | 231 | 271 | 240 | 225 | 104 | 329 |
| Percentage of Revenues | 13.1 | 14.5 | 12.5 | 12.5 | 11.0 | 12.3 | 11.9 | 11.6 | 11.2 | 14.3 | 4.6 | 5.5 | 3.6 | 3.0 | 3.2 | 3.8 | 3.4 | 2.1 | 2.8 | 2.6 | 3.2 | 2.9 | 3.3 | 5.1 | 4.4 | 2.4 | 3.9 | 5.4 | 5.1 | 4.7 | 3.7 | 4.2 | 3.9 | 3.7 | 1.7 | 5.0 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 110900.0 | 80400.0 | 107200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 23800.0 | 22300.0 | 0.0 | 0.0 | 18800.0 | 28900.0 | 21400.0 | 0.0 | 0.0 | 0.0 | 34100.0 | 0.0 | 13550.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationOtherRegions | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 |
| Value | 3747 | 4187 | 3693 | 4201 | 3414 | 3752 | 3919 | 4280 | 3703 | 4322 | 4263 | 4698 | 3902 | 4484 | 3815 | 4028 | 3701 | 3707 | 3685 | 4271 | 3626 | 3674 | 3551 | 4245 | 3618 | 4352 | 3536 | 3531 | 3169 | 4008 | 3164 | 3626 | 3218 | 3601 | 3339 | 4055 |
| Percentage of Revenues | 47.3 | 42.3 | 45.5 | 47.5 | 46.6 | 42.9 | 47.0 | 47.9 | 48.2 | 45.6 | 48.4 | 50.0 | 48.3 | 46.3 | 45.5 | 45.9 | 48.6 | 42.3 | 46.8 | 47.4 | 52.5 | 48.5 | 53.0 | 57.4 | 55.5 | 49.3 | 48.7 | 51.1 | 52.6 | 55.4 | 51.3 | 55.8 | 52.4 | 59.2 | 53.1 | 61.8 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 420100.0 | 341400.0 | 375200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 427100.0 | 362600.0 | 0.0 | 0.0 | 212250.0 | 361800.0 | 435200.0 | 0.0 | 0.0 | 0.0 | 400800.0 | 0.0 | 181300.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationReportableSegmentsTotal | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 |
| Value | 4153 | 5559 | 4331 | 4659 | 3880 | 4733 | 4644 | 4774 | 4210 | 5296 | 5069 | 5278 | 4579 | 5512 | 4654 | 4751 | 4174 | 4888 | 4388 | 5035 | 3589 | 4739 | 4294 | 4768 | 4232 | 5840 | 4802 | 4412 | 3789 | 4390 | 3772 | 4255 | 4070 | 3533 | 3898 | 4031 | 3765 | 2743 |
| Percentage of Revenues | 52.5 | 56.2 | 53.4 | 52.6 | 53.0 | 54.1 | 55.7 | 53.5 | 54.8 | 55.9 | 57.5 | 56.1 | 56.7 | 56.9 | 55.5 | 54.2 | 54.8 | 55.8 | 55.7 | 55.9 | 51.9 | 62.6 | 64.1 | 64.4 | 65.0 | 66.1 | 66.2 | 63.8 | 62.9 | 60.7 | 61.2 | 65.4 | 66.3 | 58.1 | 62.0 | 61.4 | 63.2 | 58.5 |
| Percentage of RevenueFromRelatedParties | 0.0 | 0.0 | 0.0 | 465900.0 | 388000.0 | 473300.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 503500.0 | 358900.0 | 0.0 | 0.0 | 238400.0 | 423200.0 | 584000.0 | 0.0 | 0.0 | 0.0 | 439000.0 | 0.0 | 212750.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of RevenueFromRelatedParties exc:GenerationTotalConsolidatedGroup | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 129396 | 130000 | 129317 | 127767 | 126313 | 124677 | 124977 | 122738 | 121596 | 121593 | 119666 | 119485 | 117249 | 117018 | 116700 | 118473 | 117104 | 117068 | 114904 | 114535 | 112778 | 111742 | 95384 | 95128 | 92213 | 87391 | 86814 | 85264 | 83656 | 79468 | 79924 | 79661 | 78420 | 78243 | 78554 | 78353 | 77434 | 77628 | 55092 | 54156 | 51986 | 51376 | 52240 | 49180 |
| Percentage of Assets | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 94896 | 95687 | 94449 | 92664 | 91442 | 90061 | 90404 | 88386 | 87689 | 87889 | 86596 | 86097 | 84410 | 84453 | 84568 | 88156 | 87814 | 88777 | 87292 | 87049 | 85456 | 84537 | 68062 | 67839 | 67144 | 62753 | 62681 | 60214 | 59427 | 56690 | 56984 | 57594 | 56832 | 56830 | 56737 | 56163 | 55025 | 55439 | 40617 | 39710 | 37784 | 37355 | 38590 | 36453 |
| Percentage of Liabilities | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 73.3 | 73.6 | 73.0 | 72.5 | 72.4 | 72.2 | 72.3 | 72.0 | 72.1 | 72.3 | 72.4 | 72.1 | 72.0 | 72.2 | 72.5 | 74.4 | 75.0 | 75.8 | 76.0 | 76.0 | 75.8 | 75.7 | 71.4 | 71.3 | 72.8 | 71.8 | 72.2 | 70.6 | 71.0 | 71.3 | 71.3 | 72.3 | 72.5 | 72.6 | 72.2 | 71.7 | 71.1 | 71.4 | 73.7 | 73.3 | 72.7 | 72.7 | 73.9 | 74.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 2957 | 2985 | 2895 | 2813 | 2701 | 2711 | 2657 | 2648 | 2605 | 2654 | 2573 | 2621 | 2580 | 2489 | 2402 | 2452 | 2430 | 2399 | 2423 | 2442 | 2430 | 2504 | 2387 |
| Percentage of Liabilities | 3.1 | 3.1 | 3.1 | 3.0 | 3.0 | 3.0 | 2.9 | 3.0 | 3.0 | 3.0 | 3.0 | 3.0 | 3.1 | 2.9 | 2.8 | 2.8 | 2.8 | 2.7 | 2.8 | 2.8 | 2.8 | 3.0 | 3.5 |
| Percentage of Assets | 2.3 | 2.3 | 2.2 | 2.2 | 2.1 | 2.2 | 2.1 | 2.2 | 2.1 | 2.2 | 2.2 | 2.2 | 2.2 | 2.1 | 2.1 | 2.1 | 2.1 | 2.0 | 2.1 | 2.1 | 2.2 | 2.2 | 2.5 |
| Percentage of Assets exc:AtlanticCityElectricCompany | 66.1 | 63.8 | 67.5 | 67.0 | 66.1 | 68.1 | 67.6 | 67.6 | 67.0 | 70.2 | 69.6 | 71.0 | 71.3 | 70.5 | 69.7 | 69.9 | 69.9 | 69.5 | 70.1 | 69.6 | 70.2 | 73.8 | 70.5 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 |
| Value | 7881 | 7427 | 7453 | 7316 | 7222 | 6987 | 6951 | 6754 | 6558 | 6509 | 6362 | 6297 | 6026 | 5978 | 5963 | 5915 | 5868 | 5897 | 5856 | 6100 | 5395 | 5417 | 5418 | 5289 | 5190 | 5307 | 5325 | 5214 | 5222 | 5318 | 5306 | 5149 | 5510 | 5204 | 5141 | 5161 | 4853 | 5101 | 4904 |
| Percentage of Liabilities | 8.3 | 7.8 | 7.9 | 7.9 | 7.9 | 7.8 | 7.7 | 7.6 | 7.5 | 7.4 | 7.3 | 7.3 | 7.1 | 7.1 | 7.1 | 6.7 | 6.7 | 6.6 | 6.7 | 7.0 | 6.3 | 6.4 | 8.0 | 7.8 | 7.7 | 8.5 | 8.5 | 8.7 | 8.8 | 9.4 | 9.3 | 8.9 | 9.7 | 9.2 | 9.1 | 9.2 | 8.8 | 9.2 | 12.1 |
| Percentage of Assets | 6.1 | 5.7 | 5.8 | 5.7 | 5.7 | 5.6 | 5.6 | 5.5 | 5.4 | 5.4 | 5.3 | 5.3 | 5.1 | 5.1 | 5.1 | 5.0 | 5.0 | 5.0 | 5.1 | 5.3 | 4.8 | 4.8 | 5.7 | 5.6 | 5.6 | 6.1 | 6.1 | 6.1 | 6.2 | 6.7 | 6.6 | 6.5 | 7.0 | 6.7 | 6.5 | 6.6 | 6.3 | 6.6 | 8.9 |
| Percentage of Assets exc:BaltimoreGasAndElectricCompany | 64.7 | 63.2 | 64.0 | 64.3 | 65.5 | 64.8 | 65.4 | 65.5 | 65.5 | 65.3 | 65.5 | 66.0 | 65.2 | 65.0 | 65.5 | 66.3 | 66.8 | 66.9 | 67.3 | 68.9 | 64.8 | 64.8 | 65.3 | 65.0 | 64.7 | 65.3 | 65.9 | 65.9 | 66.3 | 66.8 | 67.5 | 67.2 | 69.2 | 68.1 | 68.6 | 68.8 | 67.4 | 69.2 | 68.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 23464 | 23228 | 23137 | 23148 | 23112 | 22301 | 22088 | 21729 | 21429 | 21242 | 20966 | 21012 | 20579 | 20296 | 20184 | 20205 | 20180 | 19895 | 19610 | 19410 | 19667 | 18580 | 18289 | 18029 | 17967 | 17793 | 17485 | 17040 | 16846 | 16704 | 16590 | 16213 | 15948 | 15897 | 15582 | 15296 | 15490 | 15530 | 15616 | 16003 | 15405 | 15415 | 14742 | 13815 |
| Percentage of Liabilities | 24.7 | 24.3 | 24.5 | 25.0 | 25.3 | 24.8 | 24.4 | 24.6 | 24.4 | 24.2 | 24.2 | 24.4 | 24.4 | 24.0 | 23.9 | 22.9 | 23.0 | 22.4 | 22.5 | 22.3 | 23.0 | 22.0 | 26.9 | 26.6 | 26.8 | 28.4 | 27.9 | 28.3 | 28.3 | 29.5 | 29.1 | 28.2 | 28.1 | 28.0 | 27.5 | 27.2 | 28.2 | 28.0 | 38.4 | 40.3 | 40.8 | 41.3 | 38.2 | 37.9 |
| Percentage of Assets | 18.1 | 17.9 | 17.9 | 18.1 | 18.3 | 17.9 | 17.7 | 17.7 | 17.6 | 17.5 | 17.5 | 17.6 | 17.6 | 17.3 | 17.3 | 17.1 | 17.2 | 17.0 | 17.1 | 16.9 | 17.4 | 16.6 | 19.2 | 19.0 | 19.5 | 20.4 | 20.1 | 20.0 | 20.1 | 21.0 | 20.8 | 20.4 | 20.3 | 20.3 | 19.8 | 19.5 | 20.0 | 20.0 | 28.3 | 29.5 | 29.6 | 30.0 | 28.2 | 28.1 |
| Percentage of Assets exc:CommonwealthEdisonCo | 66.4 | 66.7 | 67.1 | 67.6 | 68.2 | 67.3 | 67.4 | 67.2 | 67.2 | 67.3 | 67.2 | 67.5 | 67.6 | 67.6 | 67.9 | 68.1 | 69.2 | 69.2 | 69.2 | 69.3 | 70.0 | 69.1 | 68.9 | 69.0 | 69.2 | 69.2 | 68.9 | 68.6 | 68.6 | 68.8 | 68.8 | 68.4 | 68.3 | 68.4 | 68.0 | 68.1 | 68.6 | 68.8 | 68.9 | 69.6 | 68.9 | 69.1 | 68.1 | 66.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 3410 | 3420 | 3464 | 3308 | 3282 | 3270 | 3250 | 3204 | 3161 | 3139 | 3079 | 3084 | 3060 | 3053 | 3022 | 2925 | 2887 | 2838 | 2827 | 2728 | 2719 | 2832 | 2732 |
| Percentage of Liabilities | 3.6 | 3.6 | 3.7 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.6 | 3.3 | 3.3 | 3.2 | 3.2 | 3.1 | 3.2 | 3.4 | 4.0 |
| Percentage of Assets | 2.6 | 2.6 | 2.7 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.6 | 2.5 | 2.5 | 2.4 | 2.5 | 2.4 | 2.4 | 2.5 | 2.9 |
| Percentage of Assets exc:DelmarvaPowerandLightCompany | 65.2 | 65.4 | 67.4 | 66.3 | 66.1 | 67.4 | 67.3 | 67.8 | 67.5 | 67.4 | 67.1 | 67.0 | 67.1 | 69.7 | 69.4 | 68.4 | 68.2 | 67.7 | 68.1 | 67.8 | 68.5 | 71.5 | 68.8 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 32836 | 33886 | 33418 | 32448 | 31776 | 32699 | 33165 | 32391 | 32810 | 32986 | 32048 | 32247 | 31729 | 32417 | 32483 | 33947 | 35000 | 35045 | 33718 | 33829 | 33530 | 33649 | 33559 | 33555 | 32469 | 32150 | 31297 | 30693 | 30772 | 28572 | 28490 | 27947 | 27481 | 27721 | 28016 | 28160 | 27582 | 27834 | 18725 | 18063 | 17841 | 18058 | 17357 | 15614 |
| Percentage of Liabilities | 34.6 | 35.4 | 35.4 | 35.0 | 34.7 | 36.3 | 36.7 | 36.6 | 37.4 | 37.5 | 37.0 | 37.5 | 37.6 | 38.4 | 38.4 | 38.5 | 39.9 | 39.5 | 38.6 | 38.9 | 39.2 | 39.8 | 49.3 | 49.5 | 48.4 | 51.2 | 49.9 | 51.0 | 51.8 | 50.4 | 50.0 | 48.5 | 48.4 | 48.8 | 49.4 | 50.1 | 50.1 | 50.2 | 46.1 | 45.5 | 47.2 | 48.3 | 45.0 | 42.8 |
| Percentage of Assets | 25.4 | 26.1 | 25.8 | 25.4 | 25.2 | 26.2 | 26.5 | 26.4 | 27.0 | 27.1 | 26.8 | 27.0 | 27.1 | 27.7 | 27.8 | 28.7 | 29.9 | 29.9 | 29.3 | 29.5 | 29.7 | 30.1 | 35.2 | 35.3 | 35.2 | 36.8 | 36.1 | 36.0 | 36.8 | 36.0 | 35.6 | 35.1 | 35.0 | 35.4 | 35.7 | 35.9 | 35.6 | 35.9 | 34.0 | 33.4 | 34.3 | 35.1 | 33.2 | 31.7 |
| Percentage of Assets exc:ExelonGenerationCoLLC | 71.7 | 71.6 | 69.5 | 68.5 | 67.6 | 68.3 | 67.7 | 67.5 | 67.8 | 67.8 | 67.4 | 66.9 | 66.6 | 67.0 | 67.1 | 71.1 | 72.7 | 72.1 | 71.8 | 71.1 | 71.5 | 71.6 | 72.1 | 72.2 | 72.0 | 70.9 | 69.0 | 68.2 | 69.3 | 69.6 | 69.1 | 69.0 | 69.3 | 69.3 | 68.9 | 68.5 | 67.1 | 66.7 | 68.3 | 69.2 | 69.6 | 70.4 | 70.7 | 69.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 | 2015-06-30 | 2015-03-31 | 2014-12-31 | 2014-09-30 | 2014-06-30 | 2014-03-31 | 2013-12-31 | 2013-09-30 | 2013-06-30 | 2013-03-31 | 2012-12-31 | 2012-09-30 | 2012-06-30 | 2012-03-31 | 2011-12-31 | 2011-09-30 | 2011-06-30 | 2011-03-31 | 2010-12-31 | 2009-12-31 |
| Value | 8461 | 8322 | 7998 | 7846 | 7702 | 7071 | 7291 | 7243 | 6947 | 6913 | 6822 | 6937 | 6810 | 6815 | 6593 | 7938 | 7555 | 7462 | 7416 | 7649 | 7265 | 7171 | 7131 | 6845 | 6935 | 6979 | 6822 | 6947 | 6683 | 6692 | 6552 | 6726 | 6398 | 6384 | 6284 | 6596 | 6175 | 6180 | 6131 | 6305 | 6002 | 5926 | 6015 | 6367 |
| Percentage of Liabilities | 8.9 | 8.7 | 8.5 | 8.5 | 8.4 | 7.9 | 8.1 | 8.2 | 7.9 | 7.9 | 7.9 | 8.1 | 8.1 | 8.1 | 7.8 | 9.0 | 8.6 | 8.4 | 8.5 | 8.8 | 8.5 | 8.5 | 10.5 | 10.1 | 10.3 | 11.1 | 10.9 | 11.5 | 11.2 | 11.8 | 11.5 | 11.7 | 11.3 | 11.2 | 11.1 | 11.7 | 11.2 | 11.1 | 15.1 | 15.9 | 15.9 | 15.9 | 15.6 | 17.5 |
| Percentage of Assets | 6.5 | 6.4 | 6.2 | 6.1 | 6.1 | 5.7 | 5.8 | 5.9 | 5.7 | 5.7 | 5.7 | 5.8 | 5.8 | 5.8 | 5.6 | 6.7 | 6.5 | 6.4 | 6.5 | 6.7 | 6.4 | 6.4 | 7.5 | 7.2 | 7.5 | 8.0 | 7.9 | 8.1 | 8.0 | 8.4 | 8.2 | 8.4 | 8.2 | 8.2 | 8.0 | 8.4 | 8.0 | 8.0 | 11.1 | 11.6 | 11.5 | 11.5 | 11.5 | 12.9 |
| Percentage of Assets exc:PecoEnergyCo | 62.7 | 64.3 | 63.8 | 63.6 | 63.5 | 61.3 | 63.6 | 63.7 | 63.1 | 63.1 | 64.1 | 65.3 | 65.8 | 66.7 | 64.8 | 69.1 | 68.4 | 68.3 | 68.5 | 69.3 | 68.6 | 68.5 | 68.8 | 68.0 | 68.5 | 68.6 | 68.6 | 69.1 | 68.5 | 68.5 | 68.1 | 69.0 | 68.0 | 67.3 | 67.2 | 68.3 | 67.1 | 67.1 | 67.0 | 67.5 | 66.7 | 66.5 | 66.9 | 70.6 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 |
| Value | 13776 | 13736 | 13692 | 13325 | 13103 | 13027 | 13111 | 13028 | 12882 | 13004 | 12702 | 12791 | 12666 | 12556 | 12422 |
| Percentage of Liabilities | 14.5 | 14.4 | 14.5 | 14.4 | 14.3 | 14.5 | 14.5 | 14.7 | 14.7 | 14.8 | 14.7 | 14.9 | 15.0 | 14.9 | 14.7 |
| Percentage of Assets | 10.6 | 10.6 | 10.6 | 10.4 | 10.4 | 10.4 | 10.5 | 10.6 | 10.6 | 10.7 | 10.6 | 10.7 | 10.8 | 10.7 | 10.6 |
| Percentage of Assets exc:PepcoHoldingsLLC | 56.8 | 56.3 | 57.7 | 57.0 | 57.0 | 57.3 | 57.7 | 57.7 | 57.4 | 58.3 | 57.8 | 58.3 | 58.2 | 58.7 | 58.5 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 6236 | 6121 | 6061 | 6005 | 5817 | 5769 | 5754 | 5690 | 5640 | 5635 | 5559 | 5535 | 5470 | 5357 | 5299 | 5259 | 5144 | 5089 | 5035 | 4897 | 4820 | 4784 | 4668 |
| Percentage of Liabilities | 6.6 | 6.4 | 6.4 | 6.5 | 6.4 | 6.4 | 6.4 | 6.4 | 6.4 | 6.4 | 6.4 | 6.4 | 6.5 | 6.3 | 6.3 | 6.0 | 5.9 | 5.7 | 5.8 | 5.6 | 5.6 | 5.7 | 6.9 |
| Percentage of Assets | 4.8 | 4.7 | 4.7 | 4.7 | 4.6 | 4.6 | 4.6 | 4.6 | 4.6 | 4.6 | 4.6 | 4.6 | 4.7 | 4.6 | 4.5 | 4.4 | 4.4 | 4.3 | 4.4 | 4.3 | 4.3 | 4.3 | 4.9 |
| Percentage of Assets exc:PotomacElectricPowerCompany | 65.0 | 64.5 | 65.4 | 65.1 | 65.6 | 65.3 | 66.4 | 66.1 | 65.9 | 66.9 | 67.0 | 67.5 | 67.3 | 67.8 | 67.7 | 67.6 | 67.3 | 68.6 | 68.6 | 67.8 | 67.9 | 69.6 | 67.6 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 305 | 313 | 284 |
| Percentage of Liabilities | 0.3 | 0.3 | 0.3 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 26.2 | 26.6 | 24.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 95 | 95 | 61 |
| Percentage of Liabilities | 0.1 | 0.1 | 0.1 |
| Percentage of Assets | 0.1 | 0.1 | 0.0 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityNotPrimaryBeneficiary exc:CommercialAgreementVIE | 12.1 | 12.0 | 7.9 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 210 | 218 | 223 |
| Percentage of Liabilities | 0.2 | 0.2 | 0.2 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityNotPrimaryBeneficiary exc:EquityInvestmentVIE | 55.6 | 56.5 | 55.6 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 61 | 216 | 172 | 33 |
| Percentage of Liabilities | 0.1 | 0.2 | 0.2 | 0.0 |
| Percentage of Assets | 0.0 | 0.2 | 0.1 | 0.0 |
| Percentage of Assets exc:ExelonGenerationCoLLC exc:CommercialAgreementVIE us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 7.9 | 29.3 | 24.4 | 5.2 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 223 | 225 | 227 | 227 |
| Percentage of Liabilities | 0.2 | 0.2 | 0.2 | 0.3 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 | 0.2 |
| Percentage of Assets exc:ExelonGenerationCoLLC exc:EquityInvestmentVIE us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 55.6 | 55.0 | 54.4 | 51.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 11 | 16 | 21 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:AtlanticCityElectricCompany us-gaap:VariableInterestEntityPrimaryBeneficiary | 91.7 | 123.1 | 161.5 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 3564 | 3559 | 3580 |
| Percentage of Liabilities | 3.8 | 3.7 | 3.8 |
| Percentage of Assets | 2.8 | 2.7 | 2.8 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityPrimaryBeneficiary | 34.6 | 34.9 | 34.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 15 | 21 | 26 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:PepcoHoldingsLLC us-gaap:VariableInterestEntityPrimaryBeneficiary | 93.8 | 116.7 | 144.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 11 | 16 | 21 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:AtlanticCityElectricCompany us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 3563 | 3557 | 3572 |
| Percentage of Liabilities | 3.8 | 3.7 | 3.8 |
| Percentage of Assets | 2.8 | 2.7 | 2.8 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 1.0 | 2.0 | 8.0 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Recourse | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 15 | 21 | 26 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:PepcoHoldingsLLC us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 21 | 26 | 31 | 41 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:AtlanticCityElectricCompany us-gaap:VariableInterestEntityPrimaryBeneficiary | 161.5 | 185.7 | 221.4 | 241.2 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 284 | 441 | 399 | 260 |
| Percentage of Liabilities | 0.3 | 0.5 | 0.4 | 0.3 |
| Percentage of Assets | 0.2 | 0.3 | 0.3 | 0.2 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 24.1 | 38.5 | 35.6 | 24.1 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 3580 | 3507 | 3507 | 3432 |
| Percentage of Liabilities | 3.8 | 3.8 | 3.8 | 3.8 |
| Percentage of Assets | 2.8 | 2.7 | 2.8 | 2.7 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityPrimaryBeneficiary | 34.2 | 33.8 | 34.4 | 35.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 26 | 32 | 37 | 44 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:PepcoHoldingsLLC us-gaap:VariableInterestEntityPrimaryBeneficiary | 144.4 | 160.0 | 176.2 | 220.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 21 | 26 | 31 | 41 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:AtlanticCityElectricCompany us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 3572 | 3499 | 3505 | 3429 |
| Percentage of Liabilities | 3.8 | 3.8 | 3.8 | 3.8 |
| Percentage of Assets | 2.8 | 2.7 | 2.8 | 2.7 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 8.0 | 8.0 | 2.0 | 3.0 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:ExelonGenerationCoLLC us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Recourse | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 26 | 32 | 37 | 44 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets exc:PepcoHoldingsLLC us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 305 | 313 | 284 |
| Percentage of Liabilities | 0.3 | 0.3 | 0.3 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 |
| Percentage of Assets us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 26.2 | 26.6 | 24.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 95 | 95 | 61 |
| Percentage of Liabilities | 0.1 | 0.1 | 0.1 |
| Percentage of Assets | 0.1 | 0.1 | 0.0 |
| Percentage of Assets us-gaap:VariableInterestEntityNotPrimaryBeneficiary exc:CommercialAgreementVIE | 12.1 | 12.0 | 7.9 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 210 | 218 | 223 |
| Percentage of Liabilities | 0.2 | 0.2 | 0.2 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 |
| Percentage of Assets us-gaap:VariableInterestEntityNotPrimaryBeneficiary exc:EquityInvestmentVIE | 55.6 | 56.5 | 55.6 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 61 | 216 | 172 | 33 |
| Percentage of Liabilities | 0.1 | 0.2 | 0.2 | 0.0 |
| Percentage of Assets | 0.0 | 0.2 | 0.1 | 0.0 |
| Percentage of Assets exc:CommercialAgreementVIE us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 7.9 | 29.3 | 24.4 | 5.2 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 223 | 225 | 227 | 227 |
| Percentage of Liabilities | 0.2 | 0.2 | 0.2 | 0.3 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 | 0.2 |
| Percentage of Assets exc:EquityInvestmentVIE us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 55.6 | 55.0 | 54.4 | 51.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | 18032 | 17150 | 16745 |
| Percentage of Liabilities | 19.1 | 19.0 | 19.3 |
| Percentage of Assets | 13.9 | 13.7 | 14.0 |
| Percentage of Assets srt:ParentCompany | 35.6 | 34.7 | 35.3 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 3579 | 3580 | 3606 |
| Percentage of Liabilities | 3.8 | 3.7 | 3.8 |
| Percentage of Assets | 2.8 | 2.8 | 2.8 |
| Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary | 34.6 | 35.0 | 34.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 3578 | 3578 | 3598 |
| Percentage of Liabilities | 3.8 | 3.7 | 3.8 |
| Percentage of Assets | 2.8 | 2.8 | 2.8 |
| Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 1.0 | 2.0 | 8.0 |
| Percentage of Liabilities | 0.0 | 0.0 | 0.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 |
| Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Recourse | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 284 | 441 | 399 | 260 |
| Percentage of Liabilities | 0.3 | 0.5 | 0.4 | 0.3 |
| Percentage of Assets | 0.2 | 0.3 | 0.3 | 0.2 |
| Percentage of Assets us-gaap:VariableInterestEntityNotPrimaryBeneficiary | 24.1 | 38.5 | 35.6 | 24.1 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 3606 | 3539 | 3544 | 3476 |
| Percentage of Liabilities | 3.8 | 3.8 | 3.9 | 3.8 |
| Percentage of Assets | 2.8 | 2.8 | 2.8 | 2.8 |
| Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary | 34.4 | 34.1 | 34.7 | 35.4 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 3598 | 3531 | 3542 | 3473 |
| Percentage of Liabilities | 3.8 | 3.8 | 3.9 | 3.8 |
| Percentage of Assets | 2.8 | 2.8 | 2.8 | 2.8 |
| Percentage of Assets us-gaap:VariableInterestEntityPrimaryBeneficiary us-gaap:Nonrecourse | 0.0 | 0.0 | 0.0 | 0.0 |