| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding | █▁ | 190.0 | 189.0 | NA | 186.0 | 186.0 | 187.0 | NA | 186.0 | 186.0 | 185.0 | NA | 186.0 | 189.0 | 188.0 | NA | 187.0 | 186.0 | 186.0 | NA | 182.0 | 182.0 | 182.0 | NA | NA |
| us-gaap:WeightedAverageNumberOfSharesOutstandingBasic | █▁ | 187.0 | 186.0 | NA | 186.0 | 186.0 | 186.0 | NA | 186.0 | 186.0 | 185.0 | NA | 186.0 | 186.0 | 186.0 | NA | 185.0 | 184.0 | 184.0 | NA | 182.471195 | 182.471195 | 182.471195 | NA | NA |
| us-gaap:EarningsPerShareBasic | █▇▅▄▃▆▂▃▁▃▅▅▆▆▃▆▆▇▄▅▄▃ | 1.66 | 0.94 | -0.02 | -0.26 | -1.06 | 0.43 | -1.63 | -1.19 | -2.17 | -1.07 | 0.23 | -0.22 | 0.4 | 0.81 | -1.06 | 0.61 | 0.41 | 1.23 | -0.68 | -0.06 | -0.29 | -1.15 | NA | NA |
| us-gaap:EarningsPerShareDiluted | █▇▅▅▃▆▂▃▁▃▅▅▆▆▃▆▆▇▄▅▄▃ | 1.63 | 0.93 | -0.02 | -0.26 | -1.06 | 0.43 | -1.63 | -1.19 | -2.17 | -1.07 | 0.23 | -0.22 | 0.39 | 0.8 | -1.06 | 0.6 | 0.4 | 1.21 | -0.68 | -0.06 | -0.29 | -1.15 | NA | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cost Ratio us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 60.0 | 55.0 | NA | 51.0 | 47.0 | 59.0 | NA | 72.0 | 64.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Cost Ratio us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 197.0 | 173.0 | NA | 195.0 | 209.0 | 218.0 | NA | 233.0 | 187.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Cost Ratio us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:OtherProducts,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 96.0 | 95.0 | NA | 72.0 | 85.0 | 73.0 | NA | 47.0 | 25.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Cost Ratio us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 741.0 | 682.0 | NA | 552.0 | 507.0 | 585.0 | NA | 607.0 | 976.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Net profit Margin us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 60.0 | 55.0 | NA | 51.0 | 47.0 | 59.0 | NA | 72.0 | 64.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Net profit Margin us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 197.0 | 173.0 | NA | 195.0 | 209.0 | 218.0 | NA | 233.0 | 187.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| Net profit Margin us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 741.0 | 682.0 | NA | 552.0 | 507.0 | 585.0 | NA | 607.0 | 976.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| TTM Greenblatt ROC _ _ | █▇▄▄▃▆▁▃▂▅▇▇██▆▆▆█▃▅▄ | 461.0 | 312.0 | 37.0 | 22.0 | -105.0 | 219.0 | -301.0 | -52.0 | -177.0 | 92.0 | 369.0 | 406.0 | 410.0 | 412.0 | 216.0 | 288.0 | 237.0 | 418.0 | -137.0 | 106.0 | 56.0 | NA | NA | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:ComprehensiveIncomeNetOfTax | ▆▃▃▂▁▅▂▂▃▂▅▅▂█ | 500.0 | -74.0 | -86.0 | -316.0 | -579.0 | 156.0 | -428.0 | -365.0 | -273.0 | -468.0 | 226.0 | 221.0 | -427.0 | 847.0 | NA | NA | NA | NA | -388.0 | -270.0 | NA | NA | -406.0 | -853.0 |
| us-gaap:ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest | ▇▅▇▆█▁▄▅▇███▄▇ | 100.0 | -18.0 | 135.0 | 43.0 | 142.0 | -206.0 | -23.0 | -10.0 | 110.0 | 150.0 | 165.0 | 156.0 | -38.0 | 112.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest | ▇▅▅▄▄▅▄▄▅▄▆▆▄█▁▅▅▇▄▄▅▅ | 600.0 | -92.0 | 49.0 | -273.0 | -437.0 | -50.0 | -451.0 | -375.0 | -163.0 | -318.0 | 376.0 | 337.0 | -366.0 | 893.0 | -1252.0 | -17.0 | 97.0 | 479.0 | -374.0 | -274.0 | 39.0 | 34.0 | NA | NA |
| us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization | ▄▅▂▂▁▂▂▃▄▄██ | 2156.0 | 2292.0 | 1974.0 | 2038.0 | 1932.0 | 2025.0 | 2048.0 | 2120.0 | 2189.0 | 2180.0 | 2513.0 | 2485.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CostOfRevenue us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 32.0 | 25.0 | NA | 28.0 | 24.0 | 26.0 | NA | 44.0 | 35.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CostOfRevenue us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 146.0 | 123.0 | NA | 131.0 | 130.0 | 148.0 | NA | 147.0 | 132.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CostOfRevenue us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:OtherProducts,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 78.0 | 63.0 | NA | 65.0 | 75.0 | 67.0 | NA | 45.0 | 23.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CostOfRevenue us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 508.0 | 503.0 | NA | 435.0 | 446.0 | 462.0 | NA | 497.0 | 821.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest | █▇▆▆▅▇▄▅▄▆▇███▇▇▇█▅▆▆▄▁▆ | 461.0 | 312.0 | 37.0 | 22.0 | -105.0 | 219.0 | -301.0 | -52.0 | -177.0 | 92.0 | 369.0 | 406.0 | 410.0 | 412.0 | 216.0 | 288.0 | 237.0 | 418.0 | -137.0 | 106.0 | 56.0 | -197.0 | -798.0 | 14.0 |
| us-gaap:IncomeTaxExpenseBenefit | ▄▃▁▂▂▃▂▃▄▅▅▇▆▄█▄▃▄▁▃▃▁▃▃ | 111.0 | 93.0 | 20.0 | 42.0 | 45.0 | 80.0 | 54.0 | 95.0 | 116.0 | 150.0 | 157.0 | 251.0 | 180.0 | 138.0 | 272.0 | 119.0 | 99.0 | 110.0 | 6.0 | 92.0 | 68.0 | 18.0 | 92.0 | 77.0 |
| us-gaap:InterestExpense | █▄▄▄▂▂▂▂▂▂▂▂▂▁▁▁▁▁▄██▇▇█ | 67.0 | 42.0 | 43.0 | 41.0 | 32.0 | 30.0 | 31.0 | 30.0 | 30.0 | 30.0 | 31.0 | 33.0 | 32.0 | 26.0 | 27.0 | 26.0 | 25.0 | 26.0 | 46.0 | 67.0 | 66.0 | 64.0 | 62.0 | 69.0 |
| us-gaap:NetIncomeLoss | █▇▆▆▅▇▄▅▄▅▆▆▇▇▅▇▇▇▅▆▆▅▁▅ | 309.0 | 175.0 | -4.0 | -49.0 | -197.0 | 80.0 | -303.0 | -221.0 | -402.0 | -199.0 | 43.0 | -41.0 | 75.0 | 150.0 | -196.0 | 113.0 | 75.0 | 225.0 | -125.0 | -6.0 | -55.0 | -210.0 | -826.0 | -124.0 |
| us-gaap:NetIncomeLossAttributableToNoncontrollingInterest | ▄▄▃▄▄▄▁▅▆▇▇█▇▆▆▄▄▅▃▃▄▃▁▄ | 41.0 | 44.0 | 21.0 | 29.0 | 47.0 | 59.0 | -52.0 | 74.0 | 109.0 | 141.0 | 169.0 | 196.0 | 155.0 | 124.0 | 140.0 | 56.0 | 63.0 | 83.0 | -4.0 | 20.0 | 43.0 | -5.0 | -64.0 | 61.0 |
| us-gaap:NonoperatingIncomeExpense | ▇▄▁▁▁█▁▂▁▁▂▃▃▂▃▂▃▇▃▇▄▁▁▃ | 105.0 | 24.0 | -44.0 | -45.0 | -51.0 | 132.0 | -44.0 | -27.0 | -50.0 | -41.0 | -32.0 | -2.0 | -9.0 | -21.0 | -9.0 | -27.0 | -6.0 | 100.0 | -1.0 | 106.0 | 23.0 | -39.0 | -51.0 | -4.0 |
| us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax | ▂▂▂▂▁█▂▄▄▂▆▃▂ | -261.0 | -207.0 | -247.0 | -240.0 | -391.0 | 681.0 | -186.0 | 58.0 | 78.0 | -282.0 | 377.0 | -24.0 | -185.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | ▇▅█▆▇▂▇▅▆▆▆▅▃▆▅▇▅█▄▆▇█▇▁ | 255.0 | -236.0 | 422.0 | 22.0 | 229.0 | -908.0 | 162.0 | -299.0 | 44.0 | -20.0 | -28.0 | -196.0 | -596.0 | -13.0 | -118.0 | 185.0 | -136.0 | 353.0 | -315.0 | 77.0 | 198.0 | 355.0 | 262.0 | -1041.0 |
| us-gaap:OtherComprehensiveIncomeLossNetOfTax | ▇▄▆▅▅▅▅▅▆▅▆▆▃█▁▅▅▆▅▅▆▇▇▃ | 250.0 | -311.0 | 32.0 | -253.0 | -287.0 | -189.0 | -96.0 | -228.0 | 130.0 | -260.0 | 164.0 | 182.0 | -596.0 | 619.0 | -1196.0 | -186.0 | -41.0 | 171.0 | -245.0 | -284.0 | 51.0 | 249.0 | 484.0 | -790.0 |
| us-gaap:OtherNonoperatingIncomeExpense | ▃▁▂▁▂█▃▅▇▅▄▄▆ | 0.0 | -3.0 | -1.0 | -3.0 | -1.0 | 9.0 | 1.0 | 4.0 | 7.0 | 4.0 | 3.0 | 2.0 | 5.0 | NA | -1.0 | -6.0 | 9.0 | 0.0 | 1.0 | -4.0 | 15.0 | 0.0 | 1.0 | -1.0 |
| us-gaap:ProfitLoss | █▇▆▆▅▇▄▅▄▆▇▇▇█▆▇▇█▅▆▆▅▁▆ | 350.0 | 219.0 | 17.0 | -20.0 | -150.0 | 139.0 | -355.0 | -147.0 | -293.0 | -58.0 | 212.0 | 155.0 | 230.0 | 274.0 | -56.0 | 169.0 | 138.0 | 308.0 | -129.0 | 14.0 | -12.0 | -215.0 | -890.0 | -63.0 |
| us-gaap:ResearchAndDevelopmentExpense | ▂▂▄▂▁▂▂▂▂▂▂▂▄▃▄▃▃▂▂▃▂▅█▇ | 6.0 | 7.0 | 9.0 | 6.0 | 5.0 | 7.0 | 6.0 | 7.0 | 7.0 | 7.0 | 7.0 | 7.0 | 9.0 | 8.0 | 9.0 | 8.0 | 8.0 | 7.0 | 7.0 | 8.0 | 7.0 | 11.0 | 15.0 | 14.0 |
| us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax | ▅▅▃▃▂▃▃▄▄▄▇▇█▆▆▅▅▄▄▃▂▁▃▄ | 2833.0 | 2870.0 | 2392.0 | 2365.0 | 2148.0 | 2381.0 | 2436.0 | 2567.0 | 2711.0 | 2719.0 | 3344.0 | 3390.0 | 3579.0 | 3090.0 | 3174.0 | 2964.0 | 2859.0 | 2655.0 | 2537.0 | 2329.0 | 2061.0 | 1892.0 | 2451.0 | 2679.0 |
| us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems us-gaap:OperatingSegments | ▆▆▆▆▅▆▆▆▆▆▇▇█▇▇▆▆▆▁▇▅▅▇█ | 3354.0 | 3416.0 | 2928.0 | 2927.0 | 2680.0 | 2950.0 | 2999.0 | 3172.0 | 3383.0 | 3353.0 | 4135.0 | 4140.0 | 4324.0 | 3779.0 | 3971.0 | 3535.0 | 3412.0 | 3194.0 | -41.0 | 3845.0 | 2790.0 | 2593.0 | 4183.0 | 4551.0 |
| us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,aa:Alumina | ▃▄▂▃▂▃▃▄▅▅██▇▅▇▃▄▃▃▂▂▁▃▅ | 1031.0 | 1124.0 | 934.0 | 1026.0 | 892.0 | 1043.0 | 1048.0 | 1140.0 | 1309.0 | 1314.0 | 1699.0 | 1645.0 | 1604.0 | 1368.0 | 1517.0 | 1111.0 | 1133.0 | 1095.0 | 995.0 | 902.0 | 922.0 | 788.0 | 1064.0 | 1274.0 |
| us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,aa:Aluminum | ▄▄▃▃▂▃▃▃▃▃▄▄▅▄▄▄▄▃█▁▃▃▁▂ | 2105.0 | 2049.0 | 1690.0 | 1609.0 | 1477.0 | 1601.0 | 1640.0 | 1681.0 | 1761.0 | 1738.0 | 2111.0 | 2204.0 | 2417.0 | 2115.0 | 2148.0 | 2099.0 | 1991.0 | 1810.0 | 3751.0 | 918.0 | 1599.0 | 1586.0 | 1062.0 | 1134.0 |
| us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ConsolidationItems,us-gaap:StatementBusinessSegments us-gaap:OperatingSegments,aa:Bauxite | ▁▂▆▅▆▆▆█▆▅▇▅▅▅▆▇▅▅▅▅▄▁▅▇ | 218.0 | 243.0 | 304.0 | 292.0 | 311.0 | 306.0 | 311.0 | 351.0 | 313.0 | 301.0 | 325.0 | 291.0 | 303.0 | 296.0 | 306.0 | 325.0 | 288.0 | 289.0 | 293.0 | 285.0 | 269.0 | 219.0 | 301.0 | 331.0 |
| us-gaap:Revenues us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Energy,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 60.0 | 55.0 | NA | 51.0 | 47.0 | 59.0 | NA | 72.0 | 64.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:Revenues us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:Mining,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 197.0 | 173.0 | NA | 195.0 | 209.0 | 218.0 | NA | 233.0 | 187.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:Revenues us-gaap:ProductOrService,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:OtherProducts,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 96.0 | 95.0 | NA | 72.0 | 85.0 | 73.0 | NA | 47.0 | 25.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:Revenues us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee aa:MaadenJointVenture,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | █▁ | 741.0 | 682.0 | NA | 552.0 | 507.0 | 585.0 | NA | 607.0 | 976.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:SellingGeneralAndAdministrativeExpense | ▂▂▃▁▁▃▃▄▄▆▃▃▄▄▅▅▅▅██▇▇██ | 54.0 | 52.0 | 55.0 | 47.0 | 44.0 | 60.0 | 62.0 | 66.0 | 68.0 | 84.0 | 59.0 | 58.0 | 64.0 | 67.0 | 70.0 | 70.0 | 72.0 | 72.0 | 92.0 | 92.0 | 90.0 | 85.0 | 92.0 | 95.0 |
| 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 |
|---|
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:Assets | ▃▄▄▃▁▂▃▃▄▅▅▆▆▇██▇▇▇█ | 14438.0 | 14931.0 | 14860.0 | 14250.0 | 13300.0 | 13651.0 | 14631.0 | 14670.0 | 15349.0 | 15956.0 | 15938.0 | 16185.0 | 16518.0 | 17096.0 | 17447.0 | 17254.0 | 16929.0 | 17076.0 | 16741.0 | 17305.0 | NA | NA | 16413.0 | NA |
| us-gaap:Liabilities | ▄▇▆▄▁▁▃▂▃▄▃▄▅▅█▄▃▄▄▂ | 9020.0 | 10058.0 | 9844.0 | 9231.0 | 7976.0 | 7840.0 | 8745.0 | 8260.0 | 8490.0 | 8873.0 | 8544.0 | 8900.0 | 9410.0 | 9579.0 | 10649.0 | 9136.0 | 8730.0 | 8913.0 | 9044.0 | 8179.0 | NA | NA | 4900.0 | NA |
| us-gaap:LiabilitiesAndStockholdersEquity | ▃▄▄▃▁▂▃▃▄▅▅▆▆▇██▇▇▇█ | 14438.0 | 14931.0 | 14860.0 | 14250.0 | 13300.0 | 13651.0 | 14631.0 | 14670.0 | 15349.0 | 15956.0 | 15938.0 | 16185.0 | 16518.0 | 17096.0 | 17447.0 | 17254.0 | 16929.0 | 17076.0 | 16741.0 | 17305.0 | NA | NA | 16413.0 | NA |
| us-gaap:StockholdersEquity | ▂▁▁▁▂▃▃▃▄▅▅▅▄▅▃▆▆▆▆█ | 3769.0 | 3248.0 | 3311.0 | 3395.0 | 3705.0 | 4275.0 | 4112.0 | 4539.0 | 4895.0 | 5157.0 | 5389.0 | 5216.0 | 5024.0 | 5368.0 | 4523.0 | 5862.0 | 5954.0 | 5876.0 | 5654.0 | 6980.0 | NA | NA | 9442.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:AssetsCurrent | ▅█▆▅▁▂▂▃▄▅▅▅▆▅▅▄▃▂▁▃ | 4201.0 | 4891.0 | 4520.0 | 4053.0 | 3179.0 | 3333.0 | 3530.0 | 3643.0 | 3818.0 | 4114.0 | 4134.0 | 4193.0 | 4281.0 | 4149.0 | 4238.0 | 3804.0 | 3583.0 | 3404.0 | 3181.0 | 3622.0 | NA | NA | 2566.0 | NA |
| us-gaap:CashAndCashEquivalentsAtCarryingValue | ▅█▅▆▃▃▃▃▃▃▄▃▄▄▄▄▃▃▃▁▁▁▂▂ | 1652.0 | 2544.0 | 1607.0 | 1736.0 | 965.0 | 829.0 | 879.0 | 841.0 | 834.0 | 1017.0 | 1113.0 | 1022.0 | 1089.0 | 1196.0 | 1358.0 | 1119.0 | 954.0 | 804.0 | 853.0 | 241.0 | 332.0 | 359.0 | 557.0 | 521.0 |
| us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents | ▄█▄▅▂▁▁▁▁▂▂▂▂▃▃▂▂▁▁ | 1655.0 | 2547.0 | 1610.0 | 1739.0 | 968.0 | 832.0 | 883.0 | 844.0 | 837.0 | 1020.0 | 1116.0 | 1026.0 | 1095.0 | 1203.0 | 1365.0 | 1127.0 | 965.0 | 822.0 | 859.0 | NA | NA | NA | 557.0 | NA |
| us-gaap:AccountsReceivableNetCurrent | ▄▃▂▂▁▃▃▃▄▅▆██▆▆▆▅▄▄▂ | 644.0 | 587.0 | 471.0 | 516.0 | 402.0 | 570.0 | 546.0 | 596.0 | 684.0 | 758.0 | 830.0 | 1017.0 | 1025.0 | 814.0 | 811.0 | 840.0 | 789.0 | 708.0 | 668.0 | 530.0 | NA | NA | 380.0 | NA |
| us-gaap:InventoryNet | ▅▄▄▄▄▅▆▆██▆▇▇▆▄▃▂▂▁▁ | 1547.0 | 1417.0 | 1398.0 | 1398.0 | 1419.0 | 1509.0 | 1644.0 | 1649.0 | 1767.0 | 1799.0 | 1644.0 | 1666.0 | 1668.0 | 1630.0 | 1453.0 | 1323.0 | 1287.0 | 1294.0 | 1160.0 | 1192.0 | NA | NA | 1172.0 | NA |
| us-gaap:PrepaidExpenseAndOtherAssetsCurrent | ▂▂▃▄▃▃▃▂▂▃▄▂▃▃▃▁▅█▅▃ | 233.0 | 238.0 | 290.0 | 297.0 | 264.0 | 277.0 | 288.0 | 245.0 | 250.0 | 285.0 | 301.0 | 255.0 | 283.0 | 270.0 | 271.0 | 217.0 | 347.0 | 424.0 | 334.0 | 269.0 | NA | NA | 333.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:AssetsNoncurrent us-gaap:ProductOrService aa:Energy | NA | NA | 401.0 | NA | NA | NA | 509.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent us-gaap:ProductOrService aa:OtherProducts | NA | NA | 757.0 | NA | NA | NA | 761.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:HalcoMiningInc | NA | NA | 828.0 | NA | NA | NA | 923.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:AssetsNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:MaadenJointVenture | NA | NA | 7648.0 | NA | NA | NA | 7931.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:PropertyPlantAndEquipmentGross | ▇▆▇▇▇▆▇▇▇▇▇▇▇█▁█████ | 20551.0 | 20199.0 | 20522.0 | 21061.0 | 20877.0 | 20181.0 | 21715.0 | 21456.0 | 22126.0 | 22015.0 | 21807.0 | 21839.0 | 22079.0 | 22837.0 | 9138.0 | 23253.0 | 22971.0 | 23076.0 | 22550.0 | 23145.0 | NA | NA | 22118.0 | NA |
| us-gaap:ConstructionInProgressGross | NA | NA | 335.0 | NA | NA | NA | 321.0 | NA | NA | NA | 406.0 | NA | NA | NA | 387.0 | NA | NA | NA | 498.0 | NA | NA | NA | 484.0 | NA | |
| us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment | ▅▃▃▇▅▁▇▅▇▆▄▄▅▇██▆▆▃▅ | 13575.0 | 13269.0 | 13332.0 | 13811.0 | 13588.0 | 13021.0 | 13799.0 | 13527.0 | 13853.0 | 13687.0 | 13480.0 | 13484.0 | 13523.0 | 13803.0 | 13908.0 | 13971.0 | 13734.0 | 13642.0 | 13225.0 | 13536.0 | NA | NA | 12728.0 | NA |
| us-gaap:PropertyPlantAndEquipmentNet | ▁▁▂▂▂▂▄▄▅▅▅▅▅▆▇▇▇█▇█ | 6976.0 | 6930.0 | 7190.0 | 7250.0 | 7289.0 | 7160.0 | 7916.0 | 7929.0 | 8273.0 | 8328.0 | 8327.0 | 8355.0 | 8556.0 | 9034.0 | 9138.0 | 9282.0 | 9237.0 | 9434.0 | 9325.0 | 9609.0 | NA | NA | 9390.0 | NA |
| us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures | ▂▁▁▁▁▁▂▂▃▇▇▇████▇█▇ | 1113.0 | 1055.0 | 1051.0 | 1034.0 | 1037.0 | 1059.0 | 1113.0 | 1114.0 | 1141.0 | 1362.0 | 1360.0 | 1381.0 | 1390.0 | 1413.0 | 1410.0 | 1408.0 | 1378.0 | 1393.0 | 1358.0 | NA | NA | NA | NA | NA |
| us-gaap:Goodwill | NA | NA | 145.0 | NA | NA | NA | 150.0 | NA | NA | NA | 989.0 | NA | NA | NA | 989.0 | NA | NA | NA | 155.0 | 155.0 | NA | NA | 152.0 | NA | |
| us-gaap:Goodwill dei:LegalEntity,us-gaap:StatementBusinessSegments aa:AlcoaCorporation,aa:Alumina | NA | NA | 96.0 | NA | NA | NA | 100.0 | NA | NA | NA | 100.0 | NA | NA | NA | 103.0 | NA | NA | NA | 103.0 | NA | NA | NA | NA | NA | |
| us-gaap:Goodwill dei:LegalEntity,us-gaap:StatementBusinessSegments aa:AlcoaCorporation,aa:Bauxite | NA | NA | 49.0 | NA | NA | NA | 50.0 | NA | NA | NA | 51.0 | NA | NA | NA | 51.0 | NA | NA | NA | 52.0 | NA | NA | NA | NA | NA | |
| us-gaap:Goodwill us-gaap:BalanceSheetLocation us-gaap:OtherNoncurrentAssets | NA | NA | 145.0 | NA | NA | NA | 150.0 | NA | NA | NA | 151.0 | NA | NA | NA | 154.0 | NA | NA | NA | 155.0 | NA | NA | NA | NA | NA | |
| us-gaap:Goodwill us-gaap:BalanceSheetLocation,us-gaap:StatementBusinessSegments us-gaap:OtherNoncurrentAssets,aa:Alumina | NA | NA | 2.0 | NA | NA | NA | 3.0 | NA | NA | NA | 3.0 | NA | NA | NA | 4.0 | NA | NA | NA | 4.0 | NA | NA | NA | NA | NA | |
| us-gaap:Goodwill us-gaap:BalanceSheetLocation,us-gaap:StatementBusinessSegments us-gaap:OtherNoncurrentAssets,us-gaap:Corporate | NA | NA | 141.0 | NA | NA | NA | 145.0 | NA | NA | NA | 146.0 | NA | NA | NA | 148.0 | NA | NA | NA | 149.0 | NA | NA | NA | NA | NA | |
| us-gaap:Goodwill us-gaap:ConsolidationItems us-gaap:MaterialReconcilingItems | NA | NA | 141.0 | NA | NA | NA | 145.0 | NA | NA | NA | 146.0 | NA | NA | NA | 148.0 | NA | NA | NA | 149.0 | NA | NA | NA | 147.0 | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet | NA | NA | 45.0 | NA | NA | NA | 52.0 | NA | NA | NA | 57.0 | NA | NA | NA | 62.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass aa:PatentLicenseAgreement | NA | NA | 17.0 | NA | NA | NA | 17.0 | NA | NA | NA | 18.0 | NA | NA | NA | 19.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass us-gaap:ComputerSoftwareIntangibleAsset | NA | NA | 18.0 | NA | NA | NA | 24.0 | NA | NA | NA | 26.0 | NA | NA | NA | 29.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:FiniteLivedIntangibleAssetsNet us-gaap:FiniteLivedIntangibleAssetsByMajorClass us-gaap:OtherIntangibleAssets | NA | NA | 10.0 | NA | NA | NA | 11.0 | NA | NA | NA | 13.0 | NA | NA | NA | 14.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet | NA | NA | 451.0 | NA | NA | NA | 410.0 | NA | NA | NA | 301.0 | NA | NA | NA | 517.0 | 562.0 | 436.0 | NA | 449.0 | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaAluminio,us-gaap:ForeignCountry | NA | NA | 166.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaCanadaCompany,us-gaap:ForeignCountry | NA | NA | 148.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaLauralcoManagementCompany,us-gaap:ForeignCountry | NA | NA | 38.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaWolinbecCompany,us-gaap:ForeignCountry | NA | NA | 38.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity,us-gaap:IncomeTaxAuthority aa:AlcoaWorldAluminaBrasil,us-gaap:ForeignCountry | NA | NA | 80.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:ConsolidationItems us-gaap:MaterialReconcilingItems | NA | NA | 655.0 | NA | NA | NA | 642.0 | NA | NA | NA | 563.0 | NA | NA | NA | 814.0 | NA | NA | NA | 741.0 | NA | NA | NA | 589.0 | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:IncomeTaxAuthority us-gaap:DomesticCountry | NA | NA | 7.0 | NA | NA | NA | 7.0 | NA | NA | NA | 10.0 | NA | NA | NA | 6.0 | NA | NA | NA | 17.0 | NA | NA | NA | NA | NA | |
| us-gaap:DeferredTaxAssetsLiabilitiesNet us-gaap:IncomeTaxAuthority us-gaap:ForeignCountry | NA | NA | 444.0 | NA | NA | NA | 403.0 | NA | NA | NA | 291.0 | NA | NA | NA | 511.0 | NA | 432.0 | NA | 432.0 | NA | NA | NA | NA | NA | |
| us-gaap:OperatingLeaseRightOfUseAsset | ▁▂▃▄▃▃▅▅▇█ | 122.0 | 131.0 | 137.0 | 147.0 | 141.0 | 141.0 | 154.0 | 158.0 | 175.0 | 185.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:OtherAssetsNoncurrent | ▄▃▄▃▂▁▃▃▄▄▄▆▇▇██▇▇▇▅ | 1416.0 | 1402.0 | 1444.0 | 1372.0 | 1308.0 | 1228.0 | 1412.0 | 1377.0 | 1463.0 | 1480.0 | 1475.0 | 1615.0 | 1635.0 | 1701.0 | 1719.0 | 1745.0 | 1688.0 | 1674.0 | 1668.0 | 1534.0 | NA | NA | 1247.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:AccountsPayableCurrent | ▃▁▃▂▁▁▄▃▄▄▅▆▆▇█▅▄▃▃▁ | 1392.0 | 1284.0 | 1403.0 | 1360.0 | 1253.0 | 1276.0 | 1484.0 | 1418.0 | 1523.0 | 1503.0 | 1663.0 | 1711.0 | 1752.0 | 1813.0 | 1898.0 | 1618.0 | 1508.0 | 1434.0 | 1455.0 | 1252.0 | NA | NA | 1379.0 | NA |
| us-gaap:LiabilitiesCurrent | ▄█▅▂▁▁▃▃▃▅▆▆▆▆█▅▄▄▅▁ | 2671.0 | 3221.0 | 2761.0 | 2303.0 | 2241.0 | 2223.0 | 2563.0 | 2455.0 | 2531.0 | 2803.0 | 2919.0 | 3004.0 | 3013.0 | 2976.0 | 3252.0 | 2766.0 | 2608.0 | 2623.0 | 2821.0 | 2206.0 | NA | NA | 2404.0 | NA |
| us-gaap:LongTermDebtCurrent | NA | NA | 2.0 | NA | NA | NA | 1.0 | NA | NA | NA | 1.0 | NA | NA | NA | 16.0 | NA | NA | NA | 21.0 | NA | NA | NA | 18.0 | NA | |
| us-gaap:OperatingLeaseLiabilityCurrent | ▁▄▇▇▆▅█ | 49.0 | 54.0 | 60.0 | 60.0 | 58.0 | 56.0 | 61.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:OtherLiabilitiesCurrent | ▅▅▅▃▃▃▄▄▃▃▂▁▂▁▃▂▄▅█▂ | 538.0 | 554.0 | 525.0 | 415.0 | 451.0 | 435.0 | 494.0 | 484.0 | 427.0 | 437.0 | 347.0 | 319.0 | 353.0 | 294.0 | 412.0 | 376.0 | 492.0 | 568.0 | 742.0 | 390.0 | NA | NA | 558.0 | NA |
| us-gaap:TaxesPayableCurrent | ▂▂▂▁▂▁▂▁▂▇██▆▆▅▃▃▃▃▂ | 126.0 | 92.0 | 91.0 | 57.0 | 96.0 | 78.0 | 104.0 | 81.0 | 100.0 | 395.0 | 426.0 | 417.0 | 323.0 | 325.0 | 282.0 | 166.0 | 144.0 | 176.0 | 147.0 | 110.0 | NA | NA | 136.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:LiabilitiesNoncurrent us-gaap:ProductOrService aa:Energy | NA | NA | 113.0 | NA | NA | NA | 87.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LiabilitiesNoncurrent us-gaap:ProductOrService aa:OtherProducts | NA | NA | 62.0 | NA | NA | NA | 42.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LiabilitiesNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:HalcoMiningInc | NA | NA | 331.0 | NA | NA | NA | 511.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LiabilitiesNoncurrent us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName aa:MaadenJointVenture | NA | NA | 5347.0 | NA | NA | NA | 5587.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | |
| us-gaap:LongTermDebt | NA | NA | 2465.0 | NA | NA | NA | 1800.0 | NA | NA | NA | 1802.0 | NA | NA | NA | 1404.0 | NA | NA | NA | 1445.0 | NA | NA | NA | 225.0 | NA | |
| us-gaap:LongTermDebtNoncurrent | NA | NA | 2463.0 | NA | NA | NA | 1799.0 | NA | NA | 1802.0 | 1801.0 | NA | NA | NA | 1388.0 | NA | NA | NA | 1424.0 | NA | NA | NA | 207.0 | NA | |
| us-gaap:LongTermDebtAndCapitalLeaseObligations | ▅▅▇█▁▁▁▁▁ | 2216.0 | 2214.0 | 2463.0 | 2538.0 | 1800.0 | 1801.0 | 1799.0 | 1805.0 | 1804.0 | NA | 1801.0 | 1820.0 | 1916.0 | 1445.0 | 1388.0 | 1384.0 | 1418.0 | 1431.0 | 1424.0 | 1457.0 | NA | NA | 207.0 | NA |
| us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType us-gaap:OtherPostretirementBenefitPlansDefinedBenefit | NA | NA | 744.0 | NA | NA | NA | 749.0 | NA | NA | NA | 868.0 | NA | NA | NA | 1100.0 | NA | NA | NA | 1166.0 | NA | NA | NA | NA | NA | |
| us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent us-gaap:RetirementPlanType us-gaap:PensionPlansDefinedBenefit | NA | NA | 1492.0 | NA | NA | NA | 1505.0 | NA | NA | NA | 1407.0 | NA | NA | NA | 2341.0 | NA | NA | NA | 1851.0 | NA | NA | NA | NA | NA | |
| us-gaap:MinorityInterest | ▂▂▃▂▂▁▃▄▅▅▅▆▆▇████▆▇ | 1649.0 | 1625.0 | 1705.0 | 1624.0 | 1619.0 | 1536.0 | 1774.0 | 1871.0 | 1964.0 | 1926.0 | 2005.0 | 2069.0 | 2084.0 | 2149.0 | 2275.0 | 2256.0 | 2245.0 | 2287.0 | 2043.0 | 2146.0 | NA | NA | 2071.0 | NA |
| us-gaap:OperatingLeaseLiabilityNoncurrent | ▁▂▃▆▅▅█ | 76.0 | 80.0 | 82.0 | 92.0 | 90.0 | 90.0 | 100.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo | ▂▁█▇ | 24.0 | 23.0 | 33.0 | 32.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree | ▂▁█▇ | 15.0 | 14.0 | 21.0 | 20.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour | ▁▁██ | 9.0 | 9.0 | 13.0 | 13.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive | NA | NA | 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 | 22.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:StockholdersEquity | ▂▁▁▁▂▃▃▃▄▅▅▅▄▅▃▆▆▆▆█ | 3769.0 | 3248.0 | 3311.0 | 3395.0 | 3705.0 | 4275.0 | 4112.0 | 4539.0 | 4895.0 | 5157.0 | 5389.0 | 5216.0 | 5024.0 | 5368.0 | 4523.0 | 5862.0 | 5954.0 | 5876.0 | 5654.0 | 6980.0 | NA | NA | 9442.0 | NA |
| us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | ▂▁▁▁▁▂▂▃▃▃▄▃▃▄▃▄▄▄▄▅████ | 5418.0 | 4873.0 | 5016.0 | 5019.0 | 5324.0 | 5811.0 | 5886.0 | 6410.0 | 6859.0 | 7083.0 | 7394.0 | 7285.0 | 7108.0 | 7517.0 | 6798.0 | 8118.0 | 8199.0 | 8163.0 | 7697.0 | 9126.0 | 11861.0 | 11813.0 | 11513.0 | 11787.0 |
| us-gaap:AdditionalPaidInCapitalCommonStock | █▇▇▇▆▆▆▆▅▅▄▆▆▅▄▃▂▂▁ | 9695.0 | 9674.0 | 9663.0 | 9661.0 | 9655.0 | 9647.0 | 9639.0 | 9638.0 | 9629.0 | 9618.0 | 9611.0 | 9656.0 | 9650.0 | 9633.0 | 9590.0 | 9584.0 | 9559.0 | 9553.0 | 9531.0 | NA | NA | NA | NA | NA |
| us-gaap:RetainedEarningsAccumulatedDeficit | ▄▂▁▁▁▃▂▄▅████▇▆█▇▆▅ | -241.0 | -550.0 | -725.0 | -721.0 | -672.0 | -476.0 | -555.0 | -252.0 | -31.0 | 371.0 | 341.0 | 298.0 | 339.0 | 263.0 | 113.0 | 309.0 | 196.0 | 121.0 | -104.0 | NA | NA | NA | NA | NA |
| us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax | ▂▁▂▂▃▄▄▄▅▄▅▅▄▅▃▇███▆ | -5687.0 | -5878.0 | -5629.0 | -5547.0 | -5280.0 | -4898.0 | -4974.0 | -4849.0 | -4705.0 | -4834.0 | -4565.0 | -4740.0 | -4967.0 | -4530.0 | -5182.0 | -4033.0 | -3803.0 | -3800.0 | -3775.0 | -4478.0 | NA | NA | -1600.0 | NA |
| us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:NoncontrollingInterest | ▄▃▄▂▂▁▄▄▅▅▅▅▆██ | -915.0 | -974.0 | -912.0 | -1026.0 | -1040.0 | -1135.0 | -870.0 | -899.0 | -815.0 | -816.0 | -825.0 | -814.0 | -769.0 | -610.0 | -577.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:Parent | ▂▁▂▃▄▆▆▆▇▆█▇▆█▅ | -5687.0 | -5878.0 | -5629.0 | -5547.0 | -5280.0 | -4898.0 | -4974.0 | -4849.0 | -4705.0 | -4834.0 | -4565.0 | -4740.0 | -4967.0 | -4530.0 | -5182.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:MinorityInterest | ▂▂▃▂▂▁▃▄▅▅▅▆▆▇████▆▇ | 1649.0 | 1625.0 | 1705.0 | 1624.0 | 1619.0 | 1536.0 | 1774.0 | 1871.0 | 1964.0 | 1926.0 | 2005.0 | 2069.0 | 2084.0 | 2149.0 | 2275.0 | 2256.0 | 2245.0 | 2287.0 | 2043.0 | 2146.0 | NA | NA | 2071.0 | NA |
| us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue | ▇▆▁▅▇▆▁▆█▇▄▇▇▇▂▅▅▅ | 10.0 | 8.0 | 1.0 | 7.0 | 9.0 | 8.0 | 1.0 | 8.0 | 11.0 | 10.0 | 6.0 | 9.0 | 10.0 | 10.0 | 3.0 | 7.0 | 7.0 | 7.0 | NA | NA | NA | NA | NA | NA |
| us-gaap:MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders | ▂▂▂▁▂▁▃▃▂▆█▅▄█▃▃▃▂▂▃▁▂▁ | 75.0 | 62.0 | 55.0 | 46.0 | 75.0 | 31.0 | 84.0 | 102.0 | 72.0 | 214.0 | 261.0 | 181.0 | 118.0 | 267.0 | 98.0 | 89.0 | 98.0 | 57.0 | 57.0 | 92.0 | 34.0 | 50.0 | 35.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:NetCashProvidedByUsedInOperatingActivities | ▃▄▄▅▆▃▆▅▅▅█▆▁▅▇▇▆▅▆ | -86.0 | 6.0 | 38.0 | 158.0 | 288.0 | -90.0 | 262.0 | 174.0 | 82.0 | 168.0 | 535.0 | 288.0 | -430.0 | 55.0 | 455.0 | 384.0 | 311.0 | 74.0 | 239.0 | NA | NA | -359.0 | 53.0 | NA |
| us-gaap:NetCashProvidedByUsedInInvestingActivities | ▃█▂▂▂▄▂▂▁▂▂▂▂▂▁▂ | 34.0 | 514.0 | -117.0 | -78.0 | -79.0 | 107.0 | -134.0 | -76.0 | -199.0 | -59.0 | -148.0 | -83.0 | -100.0 | -74.0 | -170.0 | -104.0 | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:NetCashProvidedByUsedInFinancingActivities | ▁▇▅█▅▅▄▄▅▄▄▄▇▄▅▄ | -849.0 | 428.0 | -63.0 | 692.0 | -71.0 | -44.0 | -93.0 | -81.0 | -71.0 | -199.0 | -294.0 | -280.0 | 433.0 | -147.0 | -53.0 | -115.0 | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect | ▁█▄▇▅▄▅▄▄▄▅▄▄▄▅▅▅▄ | -892.0 | 937.0 | -129.0 | 771.0 | 136.0 | -51.0 | 39.0 | 7.0 | -183.0 | -96.0 | 90.0 | -69.0 | -108.0 | -162.0 | 238.0 | 162.0 | 143.0 | -37.0 | NA | NA | NA | NA | NA | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:DeferredIncomeTaxExpenseBenefit | ▄▄▃▃▂▄▁▃▅▅▂▄▂▃█▄▄▄▁▅ | 30.0 | 18.0 | -14.0 | -6.0 | -29.0 | 23.0 | -44.0 | -5.0 | 31.0 | 33.0 | -20.0 | 15.0 | -20.0 | -11.0 | 112.0 | 14.0 | 27.0 | 23.0 | -52.0 | 34.0 | NA | NA | 103.0 | NA |
| us-gaap:DepreciationDepletionAndAmortization | ▂▆▄▂▁▄▆▆▅▄▅▄██▇█▇▆▆▆▅▅▇▇ | 161.0 | 182.0 | 170.0 | 161.0 | 152.0 | 170.0 | 183.0 | 184.0 | 174.0 | 172.0 | 174.0 | 173.0 | 192.0 | 194.0 | 187.0 | 194.0 | 190.0 | 179.0 | 182.0 | 181.0 | 178.0 | 177.0 | 186.0 | 190.0 |
| us-gaap:IncreaseDecreaseInInventories | ▇▆▆▃▁▃▄▃▃▄▄▄▆█▇▅▄▆▅▅▃▄▂ | 116.0 | 68.0 | 99.0 | -37.0 | -143.0 | -41.0 | -26.0 | -58.0 | -36.0 | -17.0 | -1.0 | 12.0 | 98.0 | 169.0 | 136.0 | 16.0 | -16.0 | 102.0 | 24.0 | 17.0 | -34.0 | -8.0 | -120.0 | NA |
| us-gaap:NetCashProvidedByUsedInOperatingActivities | ▃▄▄▅▆▃▆▅▅▅█▆▁▅▇▇▆▅▆ | -86.0 | 6.0 | 38.0 | 158.0 | 288.0 | -90.0 | 262.0 | 174.0 | 82.0 | 168.0 | 535.0 | 288.0 | -430.0 | 55.0 | 455.0 | 384.0 | 311.0 | 74.0 | 239.0 | NA | NA | -359.0 | 53.0 | NA |
| us-gaap:NetIncomeLoss | █▇▆▆▅▇▄▅▄▅▆▆▇▇▅▇▇▇▅▆▆▅▁▅ | 309.0 | 175.0 | -4.0 | -49.0 | -197.0 | 80.0 | -303.0 | -221.0 | -402.0 | -199.0 | 43.0 | -41.0 | 75.0 | 150.0 | -196.0 | 113.0 | 75.0 | 225.0 | -125.0 | -6.0 | -55.0 | -210.0 | -826.0 | -124.0 |
| us-gaap:ProfitLoss | █▇▆▆▅▇▄▅▄▆▇▇▇█▆▇▇█▅▆▆▅▁▆ | 350.0 | 219.0 | 17.0 | -20.0 | -150.0 | 139.0 | -355.0 | -147.0 | -293.0 | -58.0 | 212.0 | 155.0 | 230.0 | 274.0 | -56.0 | 169.0 | 138.0 | 308.0 | -129.0 | 14.0 | -12.0 | -215.0 | -890.0 | -63.0 |
| us-gaap:ShareBasedCompensation | ▇▆▁▅▇▆▁▆█▇▄▇▇▇▂▅▅▅▃▄▇▆▃ | 10.0 | 8.0 | 1.0 | 7.0 | 9.0 | 8.0 | 1.0 | 8.0 | 11.0 | 10.0 | 6.0 | 9.0 | 10.0 | 10.0 | 3.0 | 7.0 | 7.0 | 7.0 | 4.0 | 6.0 | 10.0 | 8.0 | 4.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:NetCashProvidedByUsedInInvestingActivities | ▃█▂▂▂▄▂▂▁▂▂▂▂▂▁▂ | 34.0 | 514.0 | -117.0 | -78.0 | -79.0 | 107.0 | -134.0 | -76.0 | -199.0 | -59.0 | -148.0 | -83.0 | -100.0 | -74.0 | -170.0 | -104.0 | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:PaymentsToAcquirePropertyPlantAndEquipment | ▂▂▅▁▂▃▇▃▃▁█▂▃▁█▃▃▁█▂▂▂▇ | 79.0 | 75.0 | 111.0 | 74.0 | 77.0 | 91.0 | 134.0 | 87.0 | 89.0 | 69.0 | 148.0 | 82.0 | 95.0 | 74.0 | 150.0 | 96.0 | 88.0 | 71.0 | 146.0 | 86.0 | 86.0 | 86.0 | 133.0 | NA |
| us-gaap:PaymentsToAcquireInvestments | ▁▁▁▁▁▁▁▁█▁▁▁ | 1.0 | 2.0 | 6.0 | 3.0 | 2.0 | 1.0 | 0.0 | 1.0 | 110.0 | 1.0 | 1.0 | 1.0 | NA | NA | 22.0 | 8.0 | 11.0 | 25.0 | 0.0 | 0.0 | 0.0 | 3.0 | 27.0 | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:NetCashProvidedByUsedInFinancingActivities | ▁▇▅█▅▅▄▄▅▄▄▄▇▄▅▄ | -849.0 | 428.0 | -63.0 | 692.0 | -71.0 | -44.0 | -93.0 | -81.0 | -71.0 | -199.0 | -294.0 | -280.0 | 433.0 | -147.0 | -53.0 | -115.0 | NA | NA | NA | NA | NA | NA | NA | NA |
| us-gaap:ProceedsFromIssuanceOfLongTermDebt dei:LegalEntity,us-gaap:DebtInstrument aa:AlcoaNederlandHoldingBV,aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven | 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:ProceedsFromIssuanceOfLongTermDebt dei:LegalEntity,us-gaap:DebtInstrument aa:AlcoaNederlandHoldingBV,aa:FourPointOneTwoFivePercentageSeniorNotesDueTwoThousandAndTwentyNine | NA | 493.0 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| 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 | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| us-gaap:DebtInstrumentInterestRateStatedPercentage us-gaap:CreditFacility,us-gaap:DebtInstrument us-gaap:RevolvingCreditFacility,aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven | NA | 5.5e-06 | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA | NA |
| 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 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 190 | 189 | 186 | 186 | 187 | 186 | 186 | 185 | 186 | 189 | 188 | 187 | 186 | 186 | 182 | 182 | 182 |
| 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 |
| 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 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 187 | 186 | 186 | 186 | 186 | 186 | 186 | 185 | 186 | 186 | 186 | 185 | 184 | 184 | 182 | 182 | 182 |
| 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 |
| 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 | 1.66 | 0.94 | -0.02 | -0.26 | -1.06 | 0.43 | -1.63 | -1.19 | -2.17 | -1.07 | 0.23 | -0.22 | 0.4 | 0.81 | -1.06 | 0.61 | 0.41 | 1.23 | -0.68 | -0.06 | -0.29 | -1.15 |
| 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 |
| 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 | 1.63 | 0.93 | -0.02 | -0.26 | -1.06 | 0.43 | -1.63 | -1.19 | -2.17 | -1.07 | 0.23 | -0.22 | 0.39 | 0.8 | -1.06 | 0.6 | 0.4 | 1.21 | -0.68 | -0.06 | -0.29 | -1.15 |
| 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 |
| 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 | 2016-12-31 | 2016-09-30 | 2015-12-31 | 2015-09-30 |
| Value | 500 | -74.0 | -86.0 | -316.0 | -579.0 | 156 | -428.0 | -365.0 | -273.0 | -468.0 | 226 | 221 | -427.0 | 847 | -388.0 | -270.0 | -406.0 | -853.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 17.6 | -2.6 | -3.6 | -13.4 | -27.0 | 6.6 | -17.6 | -14.2 | -10.1 | -17.2 | 6.8 | 6.5 | -11.9 | 27.4 | -15.3 | -11.6 | -16.6 | -31.8 |
| 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 |
| Value | 100 | -18.0 | 135 | 43 | 142 | -206.0 | -23.0 | -10.0 | 110 | 150 | 165 | 156 | -38.0 | 112 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 3.5 | -0.6 | 5.6 | 1.8 | 6.6 | -8.7 | -0.9 | -0.4 | 4.1 | 5.5 | 4.9 | 4.6 | -1.1 | 3.6 |
| 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 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 600 | -92.0 | 49 | -273.0 | -437.0 | -50.0 | -451.0 | -375.0 | -163.0 | -318.0 | 376 | 337 | -366.0 | 893 | -1252.0 | -17.0 | 97 | 479 | -374.0 | -274.0 | 39 | 34 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 21.2 | -3.2 | 2.0 | -11.5 | -20.3 | -2.1 | -18.5 | -14.6 | -6.0 | -11.7 | 11.2 | 9.9 | -10.2 | 28.9 | -39.4 | -0.6 | 3.4 | 18.0 | -14.7 | -11.8 | 1.9 | 1.8 |
| 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 |
| Value | 2156 | 2292 | 1974 | 2038 | 1932 | 2025 | 2048 | 2120 | 2189 | 2180 | 2513 | 2485 |
| Percentage of CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 76.1 | 79.9 | 82.5 | 86.2 | 89.9 | 85.0 | 84.1 | 82.6 | 80.7 | 80.2 | 75.1 | 73.3 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 32 | 25 | 28 | 24 | 26 | 44 | 35 |
| Percentage of CostOfRevenue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.1 | 0.9 | 1.2 | 1.1 | 1.1 | 1.7 | 1.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 146 | 123 | 131 | 130 | 148 | 147 | 132 |
| Percentage of CostOfRevenue | 456.2 | 492.0 | 467.9 | 541.7 | 569.2 | 334.1 | 377.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 5.2 | 4.3 | 5.5 | 6.1 | 6.2 | 5.7 | 4.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 78 | 63 | 65 | 75 | 67 | 45 | 23 |
| Percentage of CostOfRevenue | 243.8 | 252.0 | 232.1 | 312.5 | 257.7 | 102.3 | 65.7 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 2.8 | 2.2 | 2.7 | 3.5 | 2.8 | 1.8 | 0.8 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 508 | 503 | 435 | 446 | 462 | 497 | 821 |
| Percentage of CostOfRevenue | 1587.5 | 2012.0 | 1553.6 | 1858.3 | 1776.9 | 1129.5 | 2345.7 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 17.9 | 17.5 | 18.4 | 20.8 | 19.4 | 19.4 | 30.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 |
| Value | -32000000.0 |
| Percentage of GainsLossesOnExtinguishmentOfDebt | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | -1.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour | 0.0 |
| Period End | 2021-06-30 |
| Value | -32000000.0 |
| Percentage of GainsLossesOnExtinguishmentOfDebt | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | -1.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax srt:ScenarioForecast aa:SixPointSevenFivePercentBondsDueTwoThousandTwentyFour | 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 |
| Value | 461 | 312 | 37 | 22 | -105.0 | 219 | -301.0 | -52.0 | -177.0 | 92 | 369 | 406 | 410 | 412 | 216 | 288 | 237 | 418 | -137.0 | 106 | 56 | -197.0 | -798.0 | 14 |
| 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 | 100.0 | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 16.3 | 10.9 | 1.5 | 0.9 | -4.9 | 9.2 | -12.4 | -2.0 | -6.5 | 3.4 | 11.0 | 12.0 | 11.5 | 13.3 | 6.8 | 9.7 | 8.3 | 15.7 | -5.4 | 4.6 | 2.7 | -10.4 | -32.6 | 0.5 |
| 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 |
| Value | 111 | 93 | 20 | 42 | 45 | 80 | 54 | 95 | 116 | 150 | 157 | 251 | 180 | 138 | 272 | 119 | 99 | 110 | 6.0 | 92 | 68 | 18 | 92 | 77 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 3.9 | 3.2 | 0.8 | 1.8 | 2.1 | 3.4 | 2.2 | 3.7 | 4.3 | 5.5 | 4.7 | 7.4 | 5.0 | 4.5 | 8.6 | 4.0 | 3.5 | 4.1 | 0.2 | 4.0 | 3.3 | 1.0 | 3.8 | 2.9 |
| 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 |
| Value | 67 | 42 | 43 | 41 | 32 | 30 | 31 | 30 | 30 | 30 | 31 | 33 | 32 | 26 | 27 | 26 | 25 | 26 | 46 | 67 | 66 | 64 | 62 | 69 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 2.4 | 1.5 | 1.8 | 1.7 | 1.5 | 1.3 | 1.3 | 1.2 | 1.1 | 1.1 | 0.9 | 1.0 | 0.9 | 0.8 | 0.9 | 0.9 | 0.9 | 1.0 | 1.8 | 2.9 | 3.2 | 3.4 | 2.5 | 2.6 |
| Period End | 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 |
| Value | 41 | 32 | 30 | 31 | 30 | 30 | 30 | 31 | 33 | 32 | 26 | 27 | 26 | 25 | 26 | 46 | 67 | 66 | 64 | 62 | 69 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.7 | 1.5 | 1.3 | 1.3 | 1.2 | 1.1 | 1.1 | 0.9 | 1.0 | 0.9 | 0.8 | 0.9 | 0.9 | 0.9 | 1.0 | 1.8 | 2.9 | 3.2 | 3.4 | 2.5 | 2.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MaterialReconcilingItems | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | -206.2 | -160.0 | 0.0 | 0.0 | -104.0 | -227.3 | 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 |
| Value | 309 | 175 | -4.0 | -49.0 | -197.0 | 80 | -303.0 | -221.0 | -402.0 | -199.0 | 43 | -41.0 | 75 | 150 | -196.0 | 113 | 75 | 225 | -125.0 | -6.0 | -55.0 | -210.0 | -826.0 | -124.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 10.9 | 6.1 | -0.2 | -2.1 | -9.2 | 3.4 | -12.4 | -8.6 | -14.8 | -7.3 | 1.3 | -1.2 | 2.1 | 4.9 | -6.2 | 3.8 | 2.6 | 8.5 | -4.9 | -0.3 | -2.7 | -11.1 | -33.7 | -4.6 |
| 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 | 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 |
| Value | 41 | 44 | 21 | 29 | 47 | 59 | -52.0 | 74 | 109 | 141 | 169 | 196 | 155 | 124 | 140 | 56 | 63 | 83 | -4.0 | 20 | 43 | -5.0 | -64.0 | 61 |
| 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 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.4 | 1.5 | 0.9 | 1.2 | 2.2 | 2.5 | -2.1 | 2.9 | 4.0 | 5.2 | 5.1 | 5.8 | 4.3 | 4.0 | 4.4 | 1.9 | 2.2 | 3.1 | -0.2 | 0.9 | 2.1 | -0.3 | -2.6 | 2.3 |
| 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 |
| Value | 105 | 24 | -44.0 | -45.0 | -51.0 | 132 | -44.0 | -27.0 | -50.0 | -41.0 | -32.0 | -2.0 | -9.0 | -21.0 | -9.0 | -27.0 | -6.0 | 100 | -1.0 | 106 | 23 | -39.0 | -51.0 | -4.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 3.7 | 0.8 | -1.8 | -1.9 | -2.4 | 5.5 | -1.8 | -1.1 | -1.8 | -1.5 | -1.0 | -0.1 | -0.3 | -0.7 | -0.3 | -0.9 | -0.2 | 3.8 | -0.0 | 4.6 | 1.1 | -2.1 | -2.1 | -0.1 |
| 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 |
| Value | -261.0 | -207.0 | -247.0 | -240.0 | -391.0 | 681 | -186.0 | 58 | 78 | -282.0 | 377 | -24.0 | -185.0 |
| Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | -9.2 | -7.2 | -10.3 | -10.1 | -18.2 | 28.6 | -7.6 | 2.3 | 2.9 | -10.4 | 11.3 | -0.7 | -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 |
| Value | 255 | -236.0 | 422 | 22 | 229 | -908.0 | 162 | -299.0 | 44 | -20.0 | -28.0 | -196.0 | -596.0 | -13.0 | -118.0 | 185 | -136.0 | 353 | -315.0 | 77 | 198 | 355 | 262 | -1041.0 |
| Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 9.0 | -8.2 | 17.6 | 0.9 | 10.7 | -38.1 | 6.7 | -11.6 | 1.6 | -0.7 | -0.8 | -5.8 | -16.7 | -0.4 | -3.7 | 6.2 | -4.8 | 13.3 | -12.4 | 3.3 | 9.6 | 18.8 | 10.7 | -38.9 |
| 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 |
| Value | 51 | -60.0 | 124 | 17 | 94 | -245.0 | 45 | -75.0 | 4.0 | 2.0 | -10.0 | -54.0 | -151.0 | -14.0 | -25.0 | 44 | -37.0 | 114 | -82.0 | 45 | 32 | 107 | 88 | -298.0 |
| Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | 20.0 | 25.4 | 29.4 | 77.3 | 41.0 | 27.0 | 27.8 | 25.1 | 9.1 | -10.0 | 35.7 | 27.6 | 25.3 | 107.7 | 21.2 | 23.8 | 27.2 | 32.3 | 26.0 | 58.4 | 16.2 | 30.1 | 33.6 | 28.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.8 | -2.1 | 5.2 | 0.7 | 4.4 | -10.3 | 1.8 | -2.9 | 0.1 | 0.1 | -0.3 | -1.6 | -4.2 | -0.5 | -0.8 | 1.5 | -1.3 | 4.3 | -3.2 | 1.9 | 1.6 | 5.7 | 3.6 | -11.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 204 | -176.0 | 298 | 5.0 | 135 | -663.0 | 117 | -224.0 | 40 | -22.0 | -18.0 | -142.0 | -445.0 | 1.0 | -93.0 | 141 | -99.0 |
| Percentage of OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax | 80.0 | 74.6 | 70.6 | 22.7 | 59.0 | 73.0 | 72.2 | 74.9 | 90.9 | 110.0 | 64.3 | 72.4 | 74.7 | -7.7 | 78.8 | 76.2 | 72.8 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 7.2 | -6.1 | 12.5 | 0.2 | 6.3 | -27.8 | 4.8 | -8.7 | 1.5 | -0.8 | -0.5 | -4.2 | -12.4 | 0.0 | -2.9 | 4.8 | -3.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:Parent | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 250 | -311.0 | 32 | -253.0 | -287.0 | -189.0 | -96.0 | -228.0 | 130 | -260.0 | 164 | 182 | -596.0 | 619 | -1196.0 | -186.0 | -41.0 | 171 | -245.0 | -284.0 | 51 | 249 | 484 | -790.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 8.8 | -10.8 | 1.3 | -10.7 | -13.4 | -7.9 | -3.9 | -8.9 | 4.8 | -9.6 | 4.9 | 5.4 | -16.7 | 20.0 | -37.7 | -6.3 | -1.4 | 6.4 | -9.7 | -12.2 | 2.5 | 13.2 | 19.7 | -29.5 |
| 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 |
| Value | 191 | -249.0 | -82.0 | -267.0 | -382.0 | 76 | -125.0 | -144.0 | 129 | -269.0 | 175 | 227 | -437.0 | 652 | -1149.0 | -230.0 | -3.0 | -25.0 | -161.0 | -318.0 | 1.0 | 143 | 400 | -502.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 76.4 | 80.1 | -256.2 | 105.5 | 133.1 | -40.2 | 130.2 | 63.2 | 99.2 | 103.5 | 106.7 | 124.7 | 73.3 | 105.3 | 96.1 | 123.7 | 7.3 | -14.6 | 65.7 | 112.0 | 2.0 | 57.4 | 82.6 | 63.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 6.7 | -8.7 | -3.4 | -11.3 | -17.8 | 3.2 | -5.1 | -5.6 | 4.8 | -9.9 | 5.2 | 6.7 | -12.2 | 21.1 | -36.2 | -7.8 | -0.1 | -0.9 | -6.3 | -13.7 | 0.0 | 7.6 | 16.3 | -18.7 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax 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 |
| Value | 59 | -62.0 | 114 | 14 | 95 | -265.0 | 29 | -84.0 | 1.0 | 9.0 | -11.0 | -45.0 | -159.0 | -33.0 | -47.0 | 44 | -38.0 | 196 | -84.0 | 34 | 50 | 106 | 84 | -288.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTax | 23.6 | 19.9 | 356.2 | -5.5 | -33.1 | 140.2 | -30.2 | 36.8 | 0.8 | -3.5 | -6.7 | -24.7 | 26.7 | -5.3 | 3.9 | -23.7 | 92.7 | 114.6 | 34.3 | -12.0 | 98.0 | 42.6 | 17.4 | 36.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 2.1 | -2.2 | 4.8 | 0.6 | 4.4 | -11.1 | 1.2 | -3.3 | 0.0 | 0.3 | -0.3 | -1.3 | -4.4 | -1.1 | -1.5 | 1.5 | -1.3 | 7.4 | -3.3 | 1.5 | 2.4 | 5.6 | 3.4 | -10.8 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 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 |
| Value | 0.0 | -3.0 | -1.0 | -3.0 | -1.0 | 9.0 | 1.0 | 4.0 | 7.0 | 4.0 | 3.0 | 2.0 | 5.0 | -1.0 | -6.0 | 9.0 | 0.0 | 1.0 | -4.0 | 15 | 0.0 | 1.0 | -1.0 |
| Percentage of OtherNonoperatingIncomeExpense | 0.0 | 100.0 | 100.0 | 100.0 | 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 | 0.0 | 100.0 | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 0.0 | -0.1 | -0.0 | -0.1 | -0.0 | 0.4 | 0.0 | 0.2 | 0.3 | 0.1 | 0.1 | 0.1 | 0.1 | -0.0 | -0.2 | 0.3 | 0.0 | 0.0 | -0.2 | 0.7 | 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 |
| Value | 350 | 219 | 17 | -20.0 | -150.0 | 139 | -355.0 | -147.0 | -293.0 | -58.0 | 212 | 155 | 230 | 274 | -56.0 | 169 | 138 | 308 | -129.0 | 14 | -12.0 | -215.0 | -890.0 | -63.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 12.4 | 7.6 | 0.7 | -0.8 | -7.0 | 5.8 | -14.6 | -5.7 | -10.8 | -2.1 | 6.3 | 4.6 | 6.4 | 8.9 | -1.8 | 5.7 | 4.8 | 11.6 | -5.1 | 0.6 | -0.6 | -11.4 | -36.3 | -2.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 27 | 25 | 28 | 20 | 27 | 23 | 26 |
| Percentage of ProfitLoss | 7.7 | 11.4 | -140.0 | -13.3 | 19.4 | -15.6 | -8.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.0 | 0.9 | 1.2 | 0.9 | 1.1 | 0.9 | 1.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 25 | -5.0 | 16 | -5.0 | 9.0 | 23 | 2.0 |
| Percentage of ProfitLoss | 7.1 | -2.3 | -80.0 | 3.3 | 6.5 | -15.6 | -0.7 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 0.9 | -0.2 | 0.7 | -0.2 | 0.4 | 0.9 | 0.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 |
| Value | -4.0 | -2.0 | -10.0 | -6.0 | -9.0 | -15.0 |
| Percentage of ProfitLoss | -1.1 | -0.9 | 50.0 | 4.0 | -6.5 | 10.2 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | -0.1 | -0.1 | -0.4 | -0.3 | -0.4 | -0.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 102 | 45 | -38.0 | -75.0 | -13.0 | -27.0 | -57.0 |
| Percentage of ProfitLoss | 29.1 | 20.5 | 190.0 | 50.0 | -9.4 | 18.4 | 19.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 3.6 | 1.6 | -1.6 | -3.5 | -0.5 | -1.1 | -2.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 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 |
| Value | 41 | 44 | 21 | 29 | 47 | 59 | -52.0 | 74 | 109 | 141 | 169 | 196 | 155 | 124 | 140 | 56 | 63 | 83 | -4.0 | 20 | 43 | -5.0 | -64.0 | 61 |
| Percentage of ProfitLoss | 11.7 | 20.1 | 123.5 | -145.0 | -31.3 | 42.4 | 14.6 | -50.3 | -37.2 | -243.1 | 79.7 | 126.5 | 67.4 | 45.3 | -250.0 | 33.1 | 45.7 | 26.9 | 3.1 | 142.9 | -358.3 | 2.3 | 7.2 | -96.8 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.4 | 1.5 | 0.9 | 1.2 | 2.2 | 2.5 | -2.1 | 2.9 | 4.0 | 5.2 | 5.1 | 5.8 | 4.3 | 4.0 | 4.4 | 1.9 | 2.2 | 3.1 | -0.2 | 0.9 | 2.1 | -0.3 | -2.6 | 2.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 309 | 175 | -4.0 | -49.0 | -197.0 | 80 | -303.0 | -221.0 | -402.0 | -199.0 | 43 | -41.0 | 75 | 150 | -196.0 | 113 | 75 | 225 |
| Percentage of ProfitLoss | 88.3 | 79.9 | -23.5 | 245.0 | 131.3 | 57.6 | 85.4 | 150.3 | 137.2 | 343.1 | 20.3 | -26.5 | 32.6 | 54.7 | 350.0 | 66.9 | 54.3 | 73.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 10.9 | 6.1 | -0.2 | -2.1 | -9.2 | 3.4 | -12.4 | -8.6 | -14.8 | -7.3 | 1.3 | -1.2 | 2.1 | 4.9 | -6.2 | 3.8 | 2.6 | 8.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 6.0 | 7.0 | 9.0 | 6.0 | 5.0 | 7.0 | 6.0 | 7.0 | 7.0 | 7.0 | 7.0 | 7.0 | 9.0 | 8.0 | 9.0 | 8.0 | 8.0 | 7.0 | 7.0 | 8.0 | 7.0 | 11 | 15 | 14 |
| Percentage of ResearchAndDevelopmentExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 0.2 | 0.2 | 0.4 | 0.3 | 0.2 | 0.3 | 0.2 | 0.3 | 0.3 | 0.3 | 0.2 | 0.2 | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 | 0.6 | 0.6 | 0.5 |
| 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 |
| Value | 2833 | 2870 | 2392 | 2365 | 2148 | 2381 | 2436 | 2567 | 2711 | 2719 | 3344 | 3390 | 3579 | 3090 | 3174 | 2964 | 2859 | 2655 | 2537 | 2329 | 2061 | 1892 | 2451 | 2679 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 684 | 760 | 620 | 697 | 600 | 707 | 717 | 770 | 862 | 897 | 1130 | 1098 | 1068 | 913 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 24.1 | 26.5 | 25.9 | 29.5 | 27.9 | 29.7 | 29.4 | 30.0 | 31.8 | 33.0 | 33.8 | 32.4 | 29.8 | 29.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 24.1 | 26.5 | 25.9 | 29.5 | 27.9 | 29.7 | 29.4 | 30.0 | 31.8 | 33.0 | 33.8 | 32.4 | 29.8 | 29.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Alumina | 100.0 | 100.0 | 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 |
| Value | 34 | 52 | 68 | 50 | 61 | 59 | 60 | 95 | 63 | 58 | 75 | 63 | 71 | 45 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.2 | 1.8 | 2.8 | 2.1 | 2.8 | 2.5 | 2.5 | 3.7 | 2.3 | 2.1 | 2.2 | 1.9 | 2.0 | 1.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.2 | 1.8 | 2.8 | 2.1 | 2.8 | 2.5 | 2.5 | 3.7 | 2.3 | 2.1 | 2.2 | 1.9 | 2.0 | 1.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Bauxite | 100.0 | 100.0 | 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 |
| Value | 49 | 39 | 41 | 26 | 22 | 52 | 65 | 71 | 85 | 69 | 74 | 115 | 73 | 73 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.7 | 1.4 | 1.7 | 1.1 | 1.0 | 2.2 | 2.7 | 2.8 | 3.1 | 2.5 | 2.2 | 3.4 | 2.0 | 2.4 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.7 | 1.4 | 1.7 | 1.1 | 1.0 | 2.2 | 2.7 | 2.8 | 3.1 | 2.5 | 2.2 | 3.4 | 2.0 | 2.4 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy | 100.0 | 100.0 | 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 |
| Value | 0.0 | 320 | 288 | 284 | 271 | 272 | 287 | 294 | 327 | 312 | 467 | 472 | 516 | 429 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 0.0 | 11.1 | 12.0 | 12.0 | 12.6 | 11.4 | 11.8 | 11.5 | 12.1 | 11.5 | 14.0 | 13.9 | 14.4 | 13.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 0.0 | 11.1 | 12.0 | 12.0 | 12.6 | 11.4 | 11.8 | 11.5 | 12.1 | 11.5 | 14.0 | 13.9 | 14.4 | 13.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:FlatRolledAluminum | 0.0 | 100.0 | 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 |
| Value | -46.0 | -28.0 | -5.0 | -3.0 | -8.0 | -6.0 | -2.0 | -4.0 | -8.0 | -11.0 | -13.0 | -16.0 | -20.0 | -17.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | -1.6 | -1.0 | -0.2 | -0.1 | -0.4 | -0.3 | -0.1 | -0.2 | -0.3 | -0.4 | -0.4 | -0.5 | -0.6 | -0.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | -1.6 | -1.0 | -0.2 | -0.1 | -0.4 | -0.3 | -0.1 | -0.2 | -0.3 | -0.4 | -0.4 | -0.5 | -0.6 | -0.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts | 100.0 | 100.0 | 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 |
| Value | 2112 | 1727 | 1380 | 1311 | 1202 | 1297 | 1309 | 1341 | 1382 | 1394 | 1611 | 1658 | 1871 | 1647 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 74.5 | 60.2 | 57.7 | 55.4 | 56.0 | 54.5 | 53.7 | 52.2 | 51.0 | 51.3 | 48.2 | 48.9 | 52.3 | 53.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 74.5 | 60.2 | 57.7 | 55.4 | 56.0 | 54.5 | 53.7 | 52.2 | 51.0 | 51.3 | 48.2 | 48.9 | 52.3 | 53.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:PrimaryAluminum | 100.0 | 100.0 | 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 |
| Value | 3354 | 3416 | 2928 | 2927 | 2680 | 2950 | 2999 | 3172 | 3383 | 3353 | 4135 | 4140 | 4324 | 3779 | 3971 | 3535 | 3412 | 3194 | -41.0 | 3845 | 2790 | 2593 | 4183 | 4551 |
| Percentage of RevenueFromContractWithCustomerIncludingAssessedTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 118.4 | 119.0 | 122.4 | 123.8 | 124.8 | 123.9 | 123.1 | 123.6 | 124.8 | 123.3 | 123.7 | 122.1 | 120.8 | 122.3 | 125.1 | 119.3 | 119.3 | 120.3 | -1.6 | 165.1 | 135.4 | 137.1 | 170.7 | 169.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| 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 |
| Value | 1031 | 1124 | 934 | 1026 | 892 | 1043 | 1048 | 1140 | 1309 | 1314 | 1699 | 1645 | 1604 | 1368 | 1517 | 1111 | 1133 | 1095 | 995 | 902 | 922 | 788 | 1064 | 1274 |
| Percentage of RevenueFromContractWithCustomerIncludingAssessedTax | 30.7 | 32.9 | 31.9 | 35.1 | 33.3 | 35.4 | 34.9 | 35.9 | 38.7 | 39.2 | 41.1 | 39.7 | 37.1 | 36.2 | 38.2 | 31.4 | 33.2 | 34.3 | -2426.8 | 23.5 | 33.0 | 30.4 | 25.4 | 28.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 36.4 | 39.2 | 39.0 | 43.4 | 41.5 | 43.8 | 43.0 | 44.4 | 48.3 | 48.3 | 50.8 | 48.5 | 44.8 | 44.3 | 47.8 | 37.5 | 39.6 | 41.2 | 39.2 | 38.7 | 44.7 | 41.6 | 43.4 | 47.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments aa:Alumina | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 2105 | 2049 | 1690 | 1609 | 1477 | 1601 | 1640 | 1681 | 1761 | 1738 | 2111 | 2204 | 2417 | 2115 | 2148 | 2099 | 1991 | 1810 | 3751 | 918 | 1599 | 1586 | 1062 | 1134 |
| Percentage of RevenueFromContractWithCustomerIncludingAssessedTax | 62.8 | 60.0 | 57.7 | 55.0 | 55.1 | 54.3 | 54.7 | 53.0 | 52.1 | 51.8 | 51.1 | 53.2 | 55.9 | 56.0 | 54.1 | 59.4 | 58.4 | 56.7 | -9148.8 | 23.9 | 57.3 | 61.2 | 25.4 | 24.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 74.3 | 71.4 | 70.7 | 68.0 | 68.8 | 67.2 | 67.3 | 65.5 | 65.0 | 63.9 | 63.1 | 65.0 | 67.5 | 68.4 | 67.7 | 70.8 | 69.6 | 68.2 | 147.9 | 39.4 | 77.6 | 83.8 | 43.3 | 42.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments aa:Aluminum | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 218 | 243 | 304 | 292 | 311 | 306 | 311 | 351 | 313 | 301 | 325 | 291 | 303 | 296 | 306 | 325 | 288 | 289 | 293 | 285 | 269 | 219 | 301 | 331 |
| Percentage of RevenueFromContractWithCustomerIncludingAssessedTax | 6.5 | 7.1 | 10.4 | 10.0 | 11.6 | 10.4 | 10.4 | 11.1 | 9.3 | 9.0 | 7.9 | 7.0 | 7.0 | 7.8 | 7.7 | 9.2 | 8.4 | 9.0 | -714.6 | 7.4 | 9.6 | 8.4 | 7.2 | 7.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 7.7 | 8.5 | 12.7 | 12.3 | 14.5 | 12.9 | 12.8 | 13.7 | 11.5 | 11.1 | 9.7 | 8.6 | 8.5 | 9.6 | 9.6 | 11.0 | 10.1 | 10.9 | 11.5 | 12.2 | 13.1 | 11.6 | 12.3 | 12.4 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OperatingSegments aa:Bauxite | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 60 | 55 | 51 | 47 | 59 | 72 | 64 |
| Percentage of Revenues | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 2.1 | 1.9 | 2.2 | 2.2 | 2.5 | 2.8 | 2.4 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 197 | 173 | 195 | 209 | 218 | 233 | 187 |
| Percentage of Revenues | 328.3 | 314.5 | 382.4 | 444.7 | 369.5 | 323.6 | 292.2 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 7.0 | 6.0 | 8.2 | 9.7 | 9.2 | 9.1 | 6.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 96 | 95 | 72 | 85 | 73 | 47 | 25 |
| Percentage of Revenues | 160.0 | 172.7 | 141.2 | 180.9 | 123.7 | 65.3 | 39.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 3.4 | 3.3 | 3.0 | 4.0 | 3.1 | 1.8 | 0.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 741 | 682 | 552 | 507 | 585 | 607 | 976 |
| Percentage of Revenues | 1235.0 | 1240.0 | 1082.4 | 1078.7 | 991.5 | 843.1 | 1525.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 26.2 | 23.8 | 23.3 | 23.6 | 24.6 | 23.6 | 36.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 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 |
| Value | 54 | 52 | 55 | 47 | 44 | 60 | 62 | 66 | 68 | 84 | 59 | 58 | 64 | 67 | 70 | 70 | 72 | 72 | 92 | 92 | 90 | 85 | 92 | 95 |
| Percentage of SellingGeneralAndAdministrativeExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 1.9 | 1.8 | 2.3 | 2.0 | 2.0 | 2.5 | 2.5 | 2.6 | 2.5 | 3.1 | 1.8 | 1.7 | 1.8 | 2.2 | 2.2 | 2.4 | 2.5 | 2.7 | 3.6 | 4.0 | 4.4 | 4.5 | 3.8 | 3.5 |
| 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 | 2015-12-31 |
| Value | 14438 | 14931 | 14860 | 14250 | 13300 | 13651 | 14631 | 14670 | 15349 | 15956 | 15938 | 16185 | 16518 | 17096 | 17447 | 17254 | 16929 | 17076 | 16741 | 17305 | 16413 |
| 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 |
| 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 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 12015 | 12325 | 13813 | 14798 | 14394 | 14209 |
| Percentage of Assets | 80.9 | 84.2 | 86.7 | 84.8 | 86.0 | 86.6 |
| Percentage of Assets | 80.9 | 84.2 | 86.7 | 84.8 | 86.0 | 86.6 |
| Percentage of Assets us-gaap:OperatingSegments | 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 | 2015-12-31 |
| Value | 9020 | 10058 | 9844 | 9231 | 7976 | 7840 | 8745 | 8260 | 8490 | 8873 | 8544 | 8900 | 9410 | 9579 | 10649 | 9136 | 8730 | 8913 | 9044 | 8179 | 4900 |
| 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 |
| Percentage of Assets | 62.5 | 67.4 | 66.2 | 64.8 | 60.0 | 57.4 | 59.8 | 56.3 | 55.3 | 55.6 | 53.6 | 55.0 | 57.0 | 56.0 | 61.0 | 53.0 | 51.6 | 52.2 | 54.0 | 47.3 | 29.9 |
| 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 | 2015-12-31 |
| Value | 14438 | 14931 | 14860 | 14250 | 13300 | 13651 | 14631 | 14670 | 15349 | 15956 | 15938 | 16185 | 16518 | 17096 | 17447 | 17254 | 16929 | 17076 | 16741 | 17305 | 16413 |
| Percentage of LiabilitiesAndStockholdersEquity | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| 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 | 2015-12-31 |
| Value | 3769 | 3248 | 3311 | 3395 | 3705 | 4275 | 4112 | 4539 | 4895 | 5157 | 5389 | 5216 | 5024 | 5368 | 4523 | 5862 | 5954 | 5876 | 5654 | 6980 | 9442 |
| Percentage of StockholdersEquity | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 26.1 | 21.8 | 22.3 | 23.8 | 27.9 | 31.3 | 28.1 | 30.9 | 31.9 | 32.3 | 33.8 | 32.2 | 30.4 | 31.4 | 25.9 | 34.0 | 35.2 | 34.4 | 33.8 | 40.3 | 57.5 |
| 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 | 2015-12-31 |
| Value | 4201 | 4891 | 4520 | 4053 | 3179 | 3333 | 3530 | 3643 | 3818 | 4114 | 4134 | 4193 | 4281 | 4149 | 4238 | 3804 | 3583 | 3404 | 3181 | 3622 | 2566 |
| Percentage of AssetsCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 29.1 | 32.8 | 30.4 | 28.4 | 23.9 | 24.4 | 24.1 | 24.8 | 24.9 | 25.8 | 25.9 | 25.9 | 25.9 | 24.3 | 24.3 | 22.0 | 21.2 | 19.9 | 19.0 | 20.9 | 15.6 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 119 | 106 |
| Percentage of AssetsCurrent | 2.6 | 3.0 |
| Percentage of Assets | 0.8 | 0.7 |
| Percentage of Assets aa:Energy | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 219 | 181 |
| Percentage of AssetsCurrent | 4.8 | 5.1 |
| Percentage of Assets | 1.5 | 1.2 |
| Percentage of Assets aa:OtherProducts | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 143 | 191 |
| Percentage of AssetsCurrent | 3.2 | 5.4 |
| Percentage of Assets | 1.0 | 1.3 |
| Percentage of Assets aa:HalcoMiningInc | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 1099 | 1109 |
| Percentage of AssetsCurrent | 24.3 | 31.4 |
| Percentage of Assets | 7.4 | 7.6 |
| Percentage of Assets aa:MaadenJointVenture | 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 | 2014-12-31 | 2013-12-31 |
| Value | 1652 | 2544 | 1607 | 1736 | 965 | 829 | 879 | 841 | 834 | 1017 | 1113 | 1022 | 1089 | 1196 | 1358 | 1119 | 954 | 804 | 853 | 241 | 332 | 359 | 557 | 521 | 266 | 213 |
| Percentage of CashAndCashEquivalentsAtCarryingValue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 11.4 | 17.0 | 10.8 | 12.2 | 7.3 | 6.1 | 6.0 | 5.7 | 5.4 | 6.4 | 7.0 | 6.3 | 6.6 | 7.0 | 7.8 | 6.5 | 5.6 | 4.7 | 5.1 | 1.4 | 0.0 | 0.0 | 3.4 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1607 | 879 | 1113 | 1358 | 853 | 557 |
| Percentage of CashAndCashEquivalentsAtCarryingValue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 10.8 | 6.0 | 7.0 | 7.8 | 5.1 | 3.4 |
| Percentage of Assets us-gaap:MaterialReconcilingItems | 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 | 2015-12-31 |
| Value | 1655 | 2547 | 1610 | 1739 | 968 | 832 | 883 | 844 | 837 | 1020 | 1116 | 1026 | 1095 | 1203 | 1365 | 1127 | 965 | 822 | 859 | 557 |
| Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 11.5 | 17.1 | 10.8 | 12.2 | 7.3 | 6.1 | 6.0 | 5.8 | 5.5 | 6.4 | 7.0 | 6.3 | 6.6 | 7.0 | 7.8 | 6.5 | 5.7 | 4.8 | 5.1 | 3.4 |
| 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 | 2015-12-31 |
| Value | 644 | 587 | 471 | 516 | 402 | 570 | 546 | 596 | 684 | 758 | 830 | 1017 | 1025 | 814 | 811 | 840 | 789 | 708 | 668 | 530 | 380 |
| Percentage of AccountsReceivableNetCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 4.5 | 3.9 | 3.2 | 3.6 | 3.0 | 4.2 | 3.7 | 4.1 | 4.5 | 4.8 | 5.2 | 6.3 | 6.2 | 4.8 | 4.6 | 4.9 | 4.7 | 4.1 | 4.0 | 3.1 | 2.3 |
| 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 | 2015-12-31 |
| Value | 1547 | 1417 | 1398 | 1398 | 1419 | 1509 | 1644 | 1649 | 1767 | 1799 | 1644 | 1666 | 1668 | 1630 | 1453 | 1323 | 1287 | 1294 | 1160 | 1192 | 1172 |
| Percentage of InventoryNet | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 10.7 | 9.5 | 9.4 | 9.8 | 10.7 | 11.1 | 11.2 | 11.2 | 11.5 | 11.3 | 10.3 | 10.3 | 10.1 | 9.5 | 8.3 | 7.7 | 7.6 | 7.6 | 6.9 | 6.9 | 7.1 |
| 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 | 2015-12-31 |
| Value | 233 | 238 | 290 | 297 | 264 | 277 | 288 | 245 | 250 | 285 | 301 | 255 | 283 | 270 | 271 | 217 | 347 | 424 | 334 | 269 | 333 |
| Percentage of PrepaidExpenseAndOtherAssetsCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 1.6 | 1.6 | 2.0 | 2.1 | 2.0 | 2.0 | 2.0 | 1.7 | 1.6 | 1.8 | 1.9 | 1.6 | 1.7 | 1.6 | 1.6 | 1.3 | 2.0 | 2.5 | 2.0 | 1.6 | 2.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 401 | 509 |
| Percentage of AssetsNoncurrent | 100.0 | 100.0 |
| Percentage of Assets | 2.7 | 3.5 |
| Percentage of Assets aa:Energy | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 757 | 761 |
| Percentage of AssetsNoncurrent | 188.8 | 149.5 |
| Percentage of Assets | 5.1 | 5.2 |
| Percentage of Assets aa:OtherProducts | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 828 | 923 |
| Percentage of AssetsNoncurrent | 206.5 | 181.3 |
| Percentage of Assets | 5.6 | 6.3 |
| Percentage of Assets aa:HalcoMiningInc | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 7648 | 7931 |
| Percentage of AssetsNoncurrent | 1907.2 | 1558.2 |
| Percentage of Assets | 51.5 | 54.2 |
| Percentage of Assets aa:MaadenJointVenture | 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 | 2015-12-31 |
| Value | 20551 | 20199 | 20522 | 21061 | 20877 | 20181 | 21715 | 21456 | 22126 | 22015 | 21807 | 21839 | 22079 | 22837 | 9138 | 23253 | 22971 | 23076 | 22550 | 23145 | 22118 |
| Percentage of PropertyPlantAndEquipmentGross | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 142.3 | 135.3 | 138.1 | 147.8 | 157.0 | 147.8 | 148.4 | 146.3 | 144.2 | 138.0 | 136.8 | 134.9 | 133.7 | 133.6 | 52.4 | 134.8 | 135.7 | 135.1 | 134.7 | 133.7 | 134.8 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 4180 | 3956 | 3604 | 4009 | 3773 | 3717 |
| Percentage of PropertyPlantAndEquipmentGross | 20.4 | 18.2 | 16.5 | 43.9 | 16.7 | 16.8 |
| Percentage of Assets | 28.1 | 27.0 | 22.6 | 23.0 | 22.5 | 22.6 |
| Percentage of Assets us-gaap:OperatingSegments aa:AluminaRefining us-gaap:MachineryAndEquipment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 2474 | 2415 | 2478 | 2664 | 2500 | 2405 |
| Percentage of PropertyPlantAndEquipmentGross | 12.1 | 11.1 | 11.4 | 29.2 | 11.1 | 10.9 |
| Percentage of Assets | 16.6 | 16.5 | 15.5 | 15.3 | 14.9 | 14.7 |
| Percentage of Assets us-gaap:OperatingSegments aa:AluminaRefining us-gaap:ManufacturingFacility | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 6111 | 6251 | 6489 | 6827 | 6655 |
| Percentage of PropertyPlantAndEquipmentGross | 29.8 | 28.8 | 29.8 | 74.7 | 29.5 |
| Percentage of Assets | 41.1 | 42.7 | 40.7 | 39.1 | 39.8 |
| Percentage of Assets us-gaap:OperatingSegments aa:AluminumSmeltingAndCasting us-gaap:MachineryAndEquipment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 3447 | 3457 | 3532 | 3575 | 3544 |
| Percentage of PropertyPlantAndEquipmentGross | 16.8 | 15.9 | 16.2 | 39.1 | 15.7 |
| Percentage of Assets | 23.2 | 23.6 | 22.2 | 20.5 | 21.2 |
| Percentage of Assets us-gaap:OperatingSegments aa:AluminumSmeltingAndCasting us-gaap:ManufacturingFacility | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 517 | 499 | 480 | 508 | 465 | 401 |
| Percentage of PropertyPlantAndEquipmentGross | 2.5 | 2.3 | 2.2 | 5.6 | 2.1 | 1.8 |
| Percentage of Assets | 3.5 | 3.4 | 3.0 | 2.9 | 2.8 | 2.4 |
| Percentage of Assets us-gaap:OperatingSegments aa:BauxiteMining us-gaap:MachineryAndEquipment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1119 | 1138 | 1119 | 1250 | 1194 | 986 |
| Percentage of PropertyPlantAndEquipmentGross | 5.5 | 5.2 | 5.1 | 13.7 | 5.3 | 4.5 |
| Percentage of Assets | 7.5 | 7.8 | 7.0 | 7.2 | 7.1 | 6.0 |
| Percentage of Assets us-gaap:OperatingSegments aa:BauxiteMining us-gaap:ManufacturingFacility | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 844 | 879 | 889 | 905 | 1080 | 980 |
| Percentage of PropertyPlantAndEquipmentGross | 4.1 | 4.0 | 4.1 | 9.9 | 4.8 | 4.4 |
| Percentage of Assets | 5.7 | 6.0 | 5.6 | 5.2 | 6.5 | 6.0 |
| Percentage of Assets us-gaap:OperatingSegments aa:Energy us-gaap:MachineryAndEquipment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 360 | 440 | 506 | 552 | 610 | 530 |
| Percentage of PropertyPlantAndEquipmentGross | 1.8 | 2.0 | 2.3 | 6.0 | 2.7 | 2.4 |
| Percentage of Assets | 2.4 | 3.0 | 3.2 | 3.2 | 3.6 | 3.2 |
| Percentage of Assets us-gaap:OperatingSegments aa:Energy us-gaap:ManufacturingFacility | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 465 | 293 | 282 | 288 | 309 | 306 |
| Percentage of PropertyPlantAndEquipmentGross | 2.3 | 1.3 | 1.3 | 3.2 | 1.4 | 1.4 |
| Percentage of Assets | 3.1 | 2.0 | 1.8 | 1.7 | 1.8 | 1.9 |
| Percentage of Assets us-gaap:MaterialReconcilingItems us-gaap:MachineryAndEquipment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 350 | 386 | 380 | 417 | 405 | 328 |
| Percentage of PropertyPlantAndEquipmentGross | 1.7 | 1.8 | 1.7 | 4.6 | 1.8 | 1.5 |
| Percentage of Assets | 2.4 | 2.6 | 2.4 | 2.4 | 2.4 | 2.0 |
| Percentage of Assets us-gaap:MaterialReconcilingItems us-gaap:ManufacturingFacility | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 20187 | 21394 | 21401 | 22659 | 22052 | 21634 |
| Percentage of PropertyPlantAndEquipmentGross | 98.4 | 98.5 | 98.1 | 248.0 | 97.8 | 97.8 |
| Percentage of Assets | 135.8 | 146.2 | 134.3 | 129.9 | 131.7 | 131.8 |
| Percentage of Assets aa:PropertyPlantAndEquipmentOtherThanConstructionInProgress | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 320 | 333 | 328 | 346 | 346 | 333 |
| Percentage of PropertyPlantAndEquipmentGross | 1.6 | 1.5 | 1.5 | 3.8 | 1.5 | 1.5 |
| Percentage of Assets | 2.2 | 2.3 | 2.1 | 2.0 | 2.1 | 2.0 |
| Percentage of Assets us-gaap:Land | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 12117 | 12935 | 12773 | 13557 | 13166 | 13191 |
| Percentage of PropertyPlantAndEquipmentGross | 59.0 | 59.6 | 58.6 | 148.4 | 58.4 | 59.6 |
| Percentage of Assets | 81.5 | 88.4 | 80.1 | 77.7 | 78.6 | 80.4 |
| Percentage of Assets us-gaap:MachineryAndEquipment | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 7750 | 8126 | 8300 | 8756 | 8540 | 8110 |
| Percentage of PropertyPlantAndEquipmentGross | 37.8 | 37.4 | 38.1 | 95.8 | 37.9 | 36.7 |
| Percentage of Assets | 52.2 | 55.5 | 52.1 | 50.2 | 51.0 | 49.4 |
| Percentage of Assets us-gaap:ManufacturingFacility | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 335 | 321 | 406 | 387 | 498 | 484 |
| Percentage of ConstructionInProgressGross | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 2.3 | 2.2 | 2.5 | 2.2 | 3.0 | 2.9 |
| 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 | 2015-12-31 |
| Value | 13575 | 13269 | 13332 | 13811 | 13588 | 13021 | 13799 | 13527 | 13853 | 13687 | 13480 | 13484 | 13523 | 13803 | 13908 | 13971 | 13734 | 13642 | 13225 | 13536 | 12728 |
| Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 94.0 | 88.9 | 89.7 | 96.9 | 102.2 | 95.4 | 94.3 | 92.2 | 90.3 | 85.8 | 84.6 | 83.3 | 81.9 | 80.7 | 79.7 | 81.0 | 81.1 | 79.9 | 79.0 | 78.2 | 77.5 |
| 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 | 2015-12-31 |
| Value | 6976 | 6930 | 7190 | 7250 | 7289 | 7160 | 7916 | 7929 | 8273 | 8328 | 8327 | 8355 | 8556 | 9034 | 9138 | 9282 | 9237 | 9434 | 9325 | 9609 | 9390 |
| Percentage of PropertyPlantAndEquipmentNet | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 48.3 | 46.4 | 48.4 | 50.9 | 54.8 | 52.5 | 54.1 | 54.0 | 53.9 | 52.2 | 52.2 | 51.6 | 51.8 | 52.8 | 52.4 | 53.8 | 54.6 | 55.2 | 55.7 | 55.5 | 57.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 453 | 519 | 520 | 520 | 585 | 454 |
| Percentage of PropertyPlantAndEquipmentNet | 6.3 | 6.6 | 6.2 | 5.7 | 6.3 | 4.8 |
| Percentage of Assets | 3.0 | 3.5 | 3.3 | 3.0 | 3.5 | 2.8 |
| Percentage of Assets us-gaap:MaterialReconcilingItems | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 5.0 | 4.0 | 15 | 14 | 15 | 17 |
| Percentage of PropertyPlantAndEquipmentNet | 0.1 | 0.1 | 0.2 | 0.2 | 0.2 | 0.2 |
| Percentage of Assets | 0.0 | 0.0 | 0.1 | 0.1 | 0.1 | 0.1 |
| Percentage of Assets aa:OtherGeographicalRegions | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 2282 | 2044 | 2002 | 2220 | 2053 | 2158 |
| Percentage of PropertyPlantAndEquipmentNet | 31.7 | 25.8 | 24.0 | 24.3 | 22.0 | 23.0 |
| Percentage of Assets | 15.4 | 14.0 | 12.6 | 12.7 | 12.3 | 13.1 |
| Percentage of Assets country:AU | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1215 | 1596 | 1729 | 2111 | 2228 | 1922 |
| Percentage of PropertyPlantAndEquipmentNet | 16.9 | 20.2 | 20.8 | 23.1 | 23.9 | 20.5 |
| Percentage of Assets | 8.2 | 10.9 | 10.8 | 12.1 | 13.3 | 11.7 |
| Percentage of Assets country:BR | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1002 | 1047 | 1064 | 1116 | 1161 | 1177 |
| Percentage of PropertyPlantAndEquipmentNet | 13.9 | 13.2 | 12.8 | 12.2 | 12.5 | 12.5 |
| Percentage of Assets | 6.7 | 7.2 | 6.7 | 6.4 | 6.9 | 7.2 |
| Percentage of Assets country:CA | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 218 | 209 | 321 | 316 | 273 | 293 |
| Percentage of PropertyPlantAndEquipmentNet | 3.0 | 2.6 | 3.9 | 3.5 | 2.9 | 3.1 |
| Percentage of Assets | 1.5 | 1.4 | 2.0 | 1.8 | 1.6 | 1.8 |
| Percentage of Assets country:ES | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1102 | 1160 | 1216 | 1276 | 1341 | 1397 |
| Percentage of PropertyPlantAndEquipmentNet | 15.3 | 14.7 | 14.6 | 14.0 | 14.4 | 14.9 |
| Percentage of Assets | 7.4 | 7.9 | 7.6 | 7.3 | 8.0 | 8.5 |
| Percentage of Assets country:IS | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 357 | 365 | 381 | 427 | 438 | 463 |
| Percentage of PropertyPlantAndEquipmentNet | 5.0 | 4.6 | 4.6 | 4.7 | 4.7 | 4.9 |
| Percentage of Assets | 2.4 | 2.5 | 2.4 | 2.4 | 2.6 | 2.8 |
| Percentage of Assets country:NO | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1009 | 1491 | 1599 | 1658 | 1816 | 1963 |
| Percentage of PropertyPlantAndEquipmentNet | 14.0 | 18.8 | 19.2 | 18.1 | 19.5 | 20.9 |
| Percentage of Assets | 6.8 | 10.2 | 10.0 | 9.5 | 10.8 | 12.0 |
| Percentage of Assets country:US | 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 |
| Value | 1113 | 1055 | 1051 | 1034 | 1037 | 1059 | 1113 | 1114 | 1141 | 1362 | 1360 | 1381 | 1390 | 1413 | 1410 | 1408 | 1378 | 1393 | 1358 |
| Percentage of InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 7.7 | 7.1 | 7.1 | 7.3 | 7.8 | 7.8 | 7.6 | 7.6 | 7.4 | 8.5 | 8.5 | 8.5 | 8.4 | 8.3 | 8.1 | 8.2 | 8.1 | 8.2 | 8.1 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2016-09-30 | 2015-12-31 | 2014-12-31 |
| Value | 145 | 150 | 989 | 989 | 155 | 155 | 152 | 160 |
| Percentage of Goodwill | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 1.0 | 1.0 | 6.2 | 5.7 | 0.9 | 0.9 | 0.9 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 96 | 100 | 100 | 103 | 103 |
| Percentage of Goodwill | 66.2 | 66.7 | 10.1 | 10.4 | 66.5 |
| Percentage of Assets | 0.6 | 0.7 | 0.6 | 0.6 | 0.6 |
| Percentage of Assets aa:AlcoaCorporation aa:Alumina | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 49 | 50 | 51 | 51 | 52 |
| Percentage of Goodwill | 33.8 | 33.3 | 5.2 | 5.2 | 33.5 |
| Percentage of Assets | 0.3 | 0.3 | 0.3 | 0.3 | 0.3 |
| Percentage of Assets aa:AlcoaCorporation aa:Bauxite | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 145 | 150 | 151 | 154 | 155 |
| Percentage of Goodwill | 100.0 | 100.0 | 15.3 | 15.6 | 100.0 |
| Percentage of Assets | 1.0 | 1.0 | 0.9 | 0.9 | 0.9 |
| Percentage of Assets us-gaap:OtherNoncurrentAssets | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 2.0 | 3.0 | 3.0 | 4.0 | 4.0 |
| Percentage of Goodwill | 1.4 | 2.0 | 0.3 | 0.4 | 2.6 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets us-gaap:OtherNoncurrentAssets aa:Alumina | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 141 | 145 | 146 | 148 | 149 |
| Percentage of Goodwill | 97.2 | 96.7 | 14.8 | 15.0 | 96.1 |
| Percentage of Assets | 0.9 | 1.0 | 0.9 | 0.8 | 0.9 |
| Percentage of Assets us-gaap:OtherNoncurrentAssets us-gaap:Corporate | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 141 | 145 | 146 | 148 | 149 | 147 |
| Percentage of Goodwill | 97.2 | 96.7 | 14.8 | 15.0 | 96.1 | 96.7 |
| Percentage of Assets | 0.9 | 1.0 | 0.9 | 0.8 | 0.9 | 0.9 |
| Percentage of Assets us-gaap:MaterialReconcilingItems | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 |
| Value | 45 | 52 | 57 | 62 |
| Percentage of FiniteLivedIntangibleAssetsNet | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.3 | 0.4 | 0.4 | 0.4 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 |
| Value | 17 | 17 | 18 | 19 |
| Percentage of FiniteLivedIntangibleAssetsNet | 37.8 | 32.7 | 31.6 | 30.6 |
| Percentage of Assets | 0.1 | 0.1 | 0.1 | 0.1 |
| Percentage of Assets aa:PatentLicenseAgreement | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 |
| Value | 18 | 24 | 26 | 29 |
| Percentage of FiniteLivedIntangibleAssetsNet | 40.0 | 46.2 | 45.6 | 46.8 |
| Percentage of Assets | 0.1 | 0.2 | 0.2 | 0.2 |
| Percentage of Assets us-gaap:ComputerSoftwareIntangibleAsset | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 |
| Value | 10.0 | 11 | 13 | 14 |
| Percentage of FiniteLivedIntangibleAssetsNet | 22.2 | 21.2 | 22.8 | 22.6 |
| Percentage of Assets | 0.1 | 0.1 | 0.1 | 0.1 |
| Percentage of Assets us-gaap:OtherIntangibleAssets | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2016-12-31 |
| Value | 451 | 410 | 301 | 517 | 562 | 436 | 449 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 3.0 | 2.8 | 1.9 | 3.0 | 3.3 | 2.6 | 2.7 |
| Period End | 2020-12-31 |
| Value | 166 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 36.8 |
| Percentage of Assets | 1.1 |
| Percentage of Assets aa:AlcoaAluminio us-gaap:ForeignCountry | 0.0 |
| Period End | 2020-12-31 |
| Value | 148 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 32.8 |
| Percentage of Assets | 1.0 |
| Percentage of Assets aa:AlcoaCanadaCompany us-gaap:ForeignCountry | 0.0 |
| Period End | 2020-12-31 |
| Value | 38 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 8.4 |
| Percentage of Assets | 0.3 |
| Percentage of Assets aa:AlcoaLauralcoManagementCompany us-gaap:ForeignCountry | 0.0 |
| Period End | 2020-12-31 |
| Value | 38 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 8.4 |
| Percentage of Assets | 0.3 |
| Percentage of Assets aa:AlcoaWolinbecCompany us-gaap:ForeignCountry | 0.0 |
| Period End | 2020-12-31 |
| Value | 80 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 17.7 |
| Percentage of Assets | 0.5 |
| Percentage of Assets aa:AlcoaWorldAluminaBrasil us-gaap:ForeignCountry | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 655 | 642 | 563 | 814 | 741 | 589 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 145.2 | 156.6 | 187.0 | 157.4 | 165.0 | 0.0 |
| Percentage of Assets | 4.4 | 4.4 | 3.5 | 4.7 | 4.4 | 3.6 |
| Percentage of Assets us-gaap:MaterialReconcilingItems | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 7.0 | 7.0 | 10.0 | 6.0 | 17 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 1.6 | 1.7 | 3.3 | 1.2 | 3.8 |
| Percentage of Assets | 0.0 | 0.0 | 0.1 | 0.0 | 0.1 |
| Percentage of Assets us-gaap:DomesticCountry | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2017-06-30 | 2016-12-31 |
| Value | 444 | 403 | 291 | 511 | 432 | 432 |
| Percentage of DeferredTaxAssetsLiabilitiesNet | 98.4 | 98.3 | 96.7 | 98.8 | 99.1 | 96.2 |
| Percentage of Assets | 3.0 | 2.8 | 1.8 | 2.9 | 2.6 | 2.6 |
| Percentage of Assets us-gaap:ForeignCountry | 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 | 2019-01-01 |
| Value | 122 | 131 | 137 | 147 | 141 | 141 | 154 | 158 | 175 | 185 | 201 |
| Percentage of OperatingLeaseRightOfUseAsset | 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 | 0.8 | 0.9 | 0.9 | 1.0 | 1.1 | 1.0 | 1.1 | 1.1 | 1.1 | 1.2 | 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 | 2015-12-31 |
| Value | 1416 | 1402 | 1444 | 1372 | 1308 | 1228 | 1412 | 1377 | 1463 | 1480 | 1475 | 1615 | 1635 | 1701 | 1719 | 1745 | 1688 | 1674 | 1668 | 1534 | 1247 |
| Percentage of OtherAssetsNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 9.8 | 9.4 | 9.7 | 9.6 | 9.8 | 9.0 | 9.7 | 9.4 | 9.5 | 9.3 | 9.3 | 10.0 | 9.9 | 9.9 | 9.9 | 10.1 | 10.0 | 9.8 | 10.0 | 8.9 | 7.6 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 182 | 291 | 361 | 380 | 348 | 260 |
| Percentage of OtherAssets | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 1.2 | 2.0 | 2.3 | 2.2 | 2.1 | 1.6 |
| Percentage of Assets us-gaap:MaterialReconcilingItems | 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 | 2015-12-31 |
| Value | 1392 | 1284 | 1403 | 1360 | 1253 | 1276 | 1484 | 1418 | 1523 | 1503 | 1663 | 1711 | 1752 | 1813 | 1898 | 1618 | 1508 | 1434 | 1455 | 1252 | 1379 |
| Percentage of AccountsPayableCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 9.6 | 8.6 | 9.4 | 9.5 | 9.4 | 9.3 | 10.1 | 9.7 | 9.9 | 9.4 | 10.4 | 10.6 | 10.6 | 10.6 | 10.9 | 9.4 | 8.9 | 8.4 | 8.7 | 7.2 | 8.4 |
| 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 | 2015-12-31 |
| Value | 2671 | 3221 | 2761 | 2303 | 2241 | 2223 | 2563 | 2455 | 2531 | 2803 | 2919 | 3004 | 3013 | 2976 | 3252 | 2766 | 2608 | 2623 | 2821 | 2206 | 2404 |
| Percentage of LiabilitiesCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 18.5 | 21.6 | 18.6 | 16.2 | 16.8 | 16.3 | 17.5 | 16.7 | 16.5 | 17.6 | 18.3 | 18.6 | 18.2 | 17.4 | 18.6 | 16.0 | 15.4 | 15.4 | 16.9 | 12.7 | 14.6 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 27 | 41 |
| Percentage of LiabilitiesCurrent | 1.0 | 1.6 |
| Percentage of Assets | 0.2 | 0.3 |
| Percentage of Assets aa:Energy | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 66 | 59 |
| Percentage of LiabilitiesCurrent | 2.4 | 2.3 |
| Percentage of Assets | 0.4 | 0.4 |
| Percentage of Assets aa:OtherProducts | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 206 | 156 |
| Percentage of LiabilitiesCurrent | 7.5 | 6.1 |
| Percentage of Assets | 1.4 | 1.1 |
| Percentage of Assets aa:HalcoMiningInc | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 794 | 677 |
| Percentage of LiabilitiesCurrent | 28.8 | 26.4 |
| Percentage of Assets | 5.3 | 4.6 |
| Percentage of Assets aa:MaadenJointVenture | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 2.0 | 1.0 | 1.0 | 16 | 21 | 18 |
| Percentage of LongTermDebtCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.0 | 0.0 | 0.0 | 0.1 | 0.1 | 0.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 |
| Value | 49 | 54 | 60 | 60 | 58 | 56 | 61 |
| Percentage of OperatingLeaseLiabilityCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.3 | 0.4 | 0.4 | 0.4 | 0.4 | 0.4 | 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 | 2015-12-31 |
| Value | 538 | 554 | 525 | 415 | 451 | 435 | 494 | 484 | 427 | 437 | 347 | 319 | 353 | 294 | 412 | 376 | 492 | 568 | 742 | 390 | 558 |
| Percentage of OtherLiabilitiesCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 3.7 | 3.7 | 3.5 | 2.9 | 3.4 | 3.2 | 3.4 | 3.3 | 2.8 | 2.7 | 2.2 | 2.0 | 2.1 | 1.7 | 2.4 | 2.2 | 2.9 | 3.3 | 4.4 | 2.3 | 3.4 |
| 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 | 2015-12-31 |
| Value | 126 | 92 | 91 | 57 | 96 | 78 | 104 | 81 | 100 | 395 | 426 | 417 | 323 | 325 | 282 | 166 | 144 | 176 | 147 | 110 | 136 |
| Percentage of TaxesPayableCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 0.9 | 0.6 | 0.6 | 0.4 | 0.7 | 0.6 | 0.7 | 0.6 | 0.7 | 2.5 | 2.7 | 2.6 | 2.0 | 1.9 | 1.6 | 1.0 | 0.9 | 1.0 | 0.9 | 0.6 | 0.8 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 113 | 87 |
| Percentage of LiabilitiesNoncurrent | 100.0 | 100.0 |
| Percentage of Assets | 0.8 | 0.6 |
| Percentage of Assets aa:Energy | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 62 | 42 |
| Percentage of LiabilitiesNoncurrent | 54.9 | 48.3 |
| Percentage of Assets | 0.4 | 0.3 |
| Percentage of Assets aa:OtherProducts | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 331 | 511 |
| Percentage of LiabilitiesNoncurrent | 292.9 | 587.4 |
| Percentage of Assets | 2.2 | 3.5 |
| Percentage of Assets aa:HalcoMiningInc | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 5347 | 5587 |
| Percentage of LiabilitiesNoncurrent | 4731.9 | 6421.8 |
| Percentage of Assets | 36.0 | 38.2 |
| Percentage of Assets aa:MaadenJointVenture | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 2465 | 1800 | 1802 | 1404 | 1445 | 225 |
| Percentage of LongTermDebt | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 16.6 | 12.3 | 11.3 | 8.0 | 8.6 | 1.4 |
| Period End | 2020-12-31 | 2019-12-31 | 2019-03-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 2463 | 1799 | 1802 | 1801 | 1388 | 1424 | 207 |
| Percentage of LongTermDebtNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 16.6 | 12.3 | 11.3 | 11.3 | 8.0 | 8.5 | 1.3 |
| 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 | 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 | 2015-12-31 |
| Value | 2216 | 2214 | 2463 | 2538 | 1800 | 1801 | 1799 | 1805 | 1804 | 1801 | 1820 | 1916 | 1445 | 1388 | 1384 | 1418 | 1431 | 1424 | 1457 | 207 |
| Percentage of LongTermDebtAndCapitalLeaseObligations | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 15.3 | 14.8 | 16.6 | 17.8 | 13.5 | 13.2 | 12.3 | 12.3 | 11.8 | 11.3 | 11.2 | 11.6 | 8.5 | 8.0 | 8.0 | 8.4 | 8.4 | 8.5 | 8.4 | 1.3 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 744 | 749 | 868 | 1100 | 1166 |
| Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 5.0 | 5.1 | 5.4 | 6.3 | 7.0 |
| Percentage of Assets us-gaap:OtherPostretirementBenefitPlansDefinedBenefit | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 1492 | 1505 | 1407 | 2341 | 1851 |
| Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent | 200.5 | 200.9 | 162.1 | 212.8 | 158.7 |
| Percentage of Assets | 10.0 | 10.3 | 8.8 | 13.4 | 11.1 |
| Percentage of Assets us-gaap:PensionPlansDefinedBenefit | 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 | 2015-12-31 |
| Value | 1649 | 1625 | 1705 | 1624 | 1619 | 1536 | 1774 | 1871 | 1964 | 1926 | 2005 | 2069 | 2084 | 2149 | 2275 | 2256 | 2245 | 2287 | 2043 | 2146 | 2071 |
| Percentage of MinorityInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 11.4 | 10.9 | 11.5 | 11.4 | 12.2 | 11.3 | 12.1 | 12.8 | 12.8 | 12.1 | 12.6 | 12.8 | 12.6 | 12.6 | 13.0 | 13.1 | 13.3 | 13.4 | 12.2 | 12.4 | 12.6 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 |
| Value | 76 | 80 | 82 | 92 | 90 | 90 | 100 |
| Percentage of OperatingLeaseLiabilityNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.5 | 0.5 | 0.6 | 0.6 | 0.7 | 0.7 | 0.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 24 | 23 | 33 | 32 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.2 | 0.2 | 0.2 | 0.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 15 | 14 | 21 | 20 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.1 | 0.1 | 0.1 | 0.1 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 9.0 | 9.0 | 13 | 13 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.1 | 0.1 | 0.1 | 0.1 |
| Period End | 2020-12-31 |
| Value | 8000000.0 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive | 100.0 |
| Percentage of Assets | 0.1 |
| Period End | 2020-12-31 |
| Value | 22 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive | 100.0 |
| Percentage of Assets | 0.1 |
| 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 | 2019-01-01 |
| Value | 125 | 134 | 142 | 152 | 148 | 146 | 161 | 158 | 175 | 185 | 201 |
| Percentage of OperatingLeaseLiability | 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 | 0.9 | 0.9 | 1.0 | 1.1 | 1.1 | 1.1 | 1.1 | 1.1 | 1.1 | 1.2 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 142 | 152 | 165 | 175 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDue | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 1.0 | 1.0 | 1.1 | 1.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 17 | 18 | 23 | 23 |
| Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount | 100.0 | 100.0 | 100.0 | 100.0 |
| Percentage of Assets | 0.1 | 0.1 | 0.2 | 0.2 |
| 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 | 2015-12-31 |
| Value | 3769 | 3248 | 3311 | 3395 | 3705 | 4275 | 4112 | 4539 | 4895 | 5157 | 5389 | 5216 | 5024 | 5368 | 4523 | 5862 | 5954 | 5876 | 5654 | 6980 | 9442 |
| Percentage of StockholdersEquity | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 26.1 | 21.8 | 22.3 | 23.8 | 27.9 | 31.3 | 28.1 | 30.9 | 31.9 | 32.3 | 33.8 | 32.2 | 30.4 | 31.4 | 25.9 | 34.0 | 35.2 | 34.4 | 33.8 | 40.3 | 57.5 |
| 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 | 2014-12-31 | 2013-12-31 |
| Value | 5418 | 4873 | 5016 | 5019 | 5324 | 5811 | 5886 | 6410 | 6859 | 7083 | 7394 | 7285 | 7108 | 7517 | 6798 | 8118 | 8199 | 8163 | 7697 | 9126 | 11861 | 11813 | 11513 | 11787 | 12576 | 13073 | 14789 |
| Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 37.5 | 32.6 | 33.8 | 35.2 | 40.0 | 42.6 | 40.2 | 43.7 | 44.7 | 44.4 | 46.4 | 45.0 | 43.0 | 44.0 | 39.0 | 47.0 | 48.4 | 47.8 | 46.0 | 52.7 | 0.0 | 0.0 | 70.1 | 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 | 2014-12-31 | 2013-12-31 |
| Value | -5687.0 | -5878.0 | -5629.0 | -5547.0 | -5280.0 | -4898.0 | -4974.0 | -4849.0 | -4705.0 | -4834.0 | -4565.0 | -4740.0 | -4967.0 | -4530.0 | -5182.0 | -4033.0 | -3803.0 | -3800.0 | -3775.0 | -4478.0 | -1456.0 | -1457.0 | -1600.0 | -2000.0 | -1498.0 | -1316.0 | -657.0 |
| Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | -105.0 | -120.6 | -112.2 | -110.5 | -99.2 | -84.3 | -84.5 | -75.6 | -68.6 | -68.2 | -61.7 | -65.1 | -69.9 | -60.3 | -76.2 | -49.7 | -46.4 | -46.6 | -49.0 | -49.1 | -12.3 | -12.3 | -13.9 | -17.0 | -11.9 | -10.1 | -4.4 |
| Percentage of Assets | -39.4 | -39.4 | -37.9 | -38.9 | -39.7 | -35.9 | -34.0 | -33.1 | -30.7 | -30.3 | -28.6 | -29.3 | -30.1 | -26.5 | -29.7 | -23.4 | -22.5 | -22.3 | -22.5 | -25.9 | 0.0 | 0.0 | -9.7 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets 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 | 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 |
| Value | 9695 | 9674 | 9663 | 9661 | 9655 | 9647 | 9639 | 9638 | 9629 | 9618 | 9611 | 9656 | 9650 | 9633 | 9590 | 9584 | 9559 | 9553 | 9531 |
| Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 178.9 | 198.5 | 192.6 | 192.5 | 181.3 | 166.0 | 163.8 | 150.4 | 140.4 | 135.8 | 130.0 | 132.5 | 135.8 | 128.1 | 141.1 | 118.1 | 116.6 | 117.0 | 123.8 |
| Percentage of Assets | 67.1 | 64.8 | 65.0 | 67.8 | 72.6 | 70.7 | 65.9 | 65.7 | 62.7 | 60.3 | 60.3 | 59.7 | 58.4 | 56.3 | 55.0 | 55.5 | 56.5 | 55.9 | 56.9 |
| Percentage of Assets us-gaap:AdditionalPaidInCapital | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 2014-12-31 | 2013-12-31 |
| Value | 1649 | 1625 | 1705 | 1624 | 1619 | 1536 | 1774 | 1871 | 1964 | 1926 | 2005 | 2069 | 2084 | 2149 | 2275 | 2256 | 2245 | 2287 | 2043 | 2146 | 2180 | 2122 | 2071 | 2084 | 2311 | 2474 | 2896 |
| Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | 30.4 | 33.3 | 34.0 | 32.4 | 30.4 | 26.4 | 30.1 | 29.2 | 28.6 | 27.2 | 27.1 | 28.4 | 29.3 | 28.6 | 33.5 | 27.8 | 27.4 | 28.0 | 26.5 | 23.5 | 18.4 | 18.0 | 18.0 | 17.7 | 18.4 | 18.9 | 19.6 |
| Percentage of Assets | 11.4 | 10.9 | 11.5 | 11.4 | 12.2 | 11.3 | 12.1 | 12.8 | 12.8 | 12.1 | 12.6 | 12.8 | 12.6 | 12.6 | 13.0 | 13.1 | 13.3 | 13.4 | 12.2 | 12.4 | 0.0 | 0.0 | 12.6 | 0.0 | 0.0 | 0.0 | 0.0 |
| Percentage of Assets us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | -241.0 | -550.0 | -725.0 | -721.0 | -672.0 | -476.0 | -555.0 | -252.0 | -31.0 | 371 | 341 | 298 | 339 | 263 | 113 | 309 | 196 | 121 | -104.0 |
| Percentage of StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest | -4.4 | -11.3 | -14.5 | -14.4 | -12.6 | -8.2 | -9.4 | -3.9 | -0.5 | 5.2 | 4.6 | 4.1 | 4.8 | 3.5 | 1.7 | 3.8 | 2.4 | 1.5 | -1.4 |
| Percentage of Assets | -1.7 | -3.7 | -4.9 | -5.1 | -5.1 | -3.5 | -3.8 | -1.7 | -0.2 | 2.3 | 2.1 | 1.8 | 2.1 | 1.5 | 0.6 | 1.8 | 1.2 | 0.7 | -0.6 |
| Percentage of Assets us-gaap:RetainedEarnings | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 9695 | 9674 | 9663 | 9661 | 9655 | 9647 | 9639 | 9638 | 9629 | 9618 | 9611 | 9656 | 9650 | 9633 | 9590 | 9584 | 9559 | 9553 | 9531 |
| Percentage of AdditionalPaidInCapitalCommonStock | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 67.1 | 64.8 | 65.0 | 67.8 | 72.6 | 70.7 | 65.9 | 65.7 | 62.7 | 60.3 | 60.3 | 59.7 | 58.4 | 56.3 | 55.0 | 55.5 | 56.5 | 55.9 | 56.9 |
| 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 |
| Value | -241.0 | -550.0 | -725.0 | -721.0 | -672.0 | -476.0 | -555.0 | -252.0 | -31.0 | 371 | 341 | 298 | 339 | 263 | 113 | 309 | 196 | 121 | -104.0 |
| Percentage of RetainedEarningsAccumulatedDeficit | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | -1.7 | -3.7 | -4.9 | -5.1 | -5.1 | -3.5 | -3.8 | -1.7 | -0.2 | 2.3 | 2.1 | 1.8 | 2.1 | 1.5 | 0.6 | 1.8 | 1.2 | 0.7 | -0.6 |
| 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 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2015-12-31 |
| Value | -5687000000.0 | -5878000000.0 | -5629000000.0 | -5547000000.0 | -5280000000.0 | -4898000000.0 | -4974000000.0 | -4849000000.0 | -4705000000.0 | -4834000000.0 | -4565000000.0 | -4740000000.0 | -4967000000.0 | -4530000000.0 | -5182000000.0 | -4033000000.0 | -3803000000.0 | -3800000000.0 | -3775000000.0 | -4478000000.0 | -1600000000.0 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | -39.4 | -39.4 | -37.9 | -38.9 | -39.7 | -35.9 | -34.0 | -33.1 | -30.7 | -30.3 | -28.6 | -29.3 | -30.1 | -26.5 | -29.7 | -23.4 | -22.5 | -22.3 | -22.5 | -25.9 | -9.7 |
| 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 |
| Value | -915000000.0 | -974000000.0 | -912000000.0 | -1026000000.0 | -1040000000.0 | -1135000000.0 | -870000000.0 | -899000000.0 | -815000000.0 | -816000000.0 | -825000000.0 | -814000000.0 | -769000000.0 | -610000000.0 | -577000000.0 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax | 16.1 | 16.6 | 16.2 | 18.5 | 19.7 | 23.2 | 17.5 | 18.5 | 17.3 | 16.9 | 18.1 | 17.2 | 15.5 | 13.5 | 11.1 |
| Percentage of Assets | -6.3 | -6.5 | -6.1 | -7.2 | -7.8 | -8.3 | -5.9 | -6.1 | -5.3 | -5.1 | -5.2 | -5.0 | -4.7 | -3.6 | -3.3 |
| Percentage of Assets us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 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 |
| Value | -5687000000.0 | -5878000000.0 | -5629000000.0 | -5547000000.0 | -5280000000.0 | -4898000000.0 | -4974000000.0 | -4849000000.0 | -4705000000.0 | -4834000000.0 | -4565000000.0 | -4740000000.0 | -4967000000.0 | -4530000000.0 | -5182000000.0 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax | 100.0 | 100.0 | 100.0 | 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 | -39.4 | -39.4 | -37.9 | -38.9 | -39.7 | -35.9 | -34.0 | -33.1 | -30.7 | -30.3 | -28.6 | -29.3 | -30.1 | -26.5 | -29.7 |
| Percentage of Assets us-gaap:Parent | 0.0 | 0.0 | 0.0 | 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 | 2015-12-31 |
| Value | 1649 | 1625 | 1705 | 1624 | 1619 | 1536 | 1774 | 1871 | 1964 | 1926 | 2005 | 2069 | 2084 | 2149 | 2275 | 2256 | 2245 | 2287 | 2043 | 2146 | 2071 |
| Percentage of MinorityInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 11.4 | 10.9 | 11.5 | 11.4 | 12.2 | 11.3 | 12.1 | 12.8 | 12.8 | 12.1 | 12.6 | 12.8 | 12.6 | 12.6 | 13.0 | 13.1 | 13.3 | 13.4 | 12.2 | 12.4 | 12.6 |
| 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 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 10.0 | 8.0 | 1.0 | 7.0 | 9.0 | 8.0 | 1.0 | 8.0 | 11 | 10.0 | 6.0 | 9.0 | 10.0 | 10.0 | 3.0 | 7.0 | 7.0 | 7.0 |
| Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 8.0 | 1.0 | 7.0 | 9.0 | 8.0 | 1.0 | 8.0 | 11 | 10.0 | 6.0 | 9.0 | 10.0 | 10.0 | 3.0 | 7.0 | 7.0 | 7.0 |
| Percentage of AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 Assets us-gaap:AdditionalPaidInCapital | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 75 | 62 | 55 | 46 | 75 | 31 | 84 | 102 | 72 | 214 | 261 | 181 | 118 | 267 | 98 | 89 | 98 | 57 | 57 | 92 | 34 | 50 | 35 |
| Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 75 | 62 | 55 | 46 | 75 | 31 | 84 | 102 | 72 | 214 | 261 | 181 | 118 | 267 | 98 | 89 | 98 | 57 | 57 | 92 | 34 | 50 | 35 |
| Percentage of MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 Assets us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 2016-03-31 | 2015-12-31 |
| Value | -86.0 | 6.0 | 38 | 158 | 288 | -90.0 | 262 | 174 | 82 | 168 | 535 | 288 | -430.0 | 55 | 455 | 384 | 311 | 74 | 239 | -359.0 | 53 |
| Percentage of NetCashProvidedByUsedInOperatingActivities | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | -3.0 | 0.2 | 1.6 | 6.7 | 13.4 | -3.8 | 10.8 | 6.8 | 3.0 | 6.2 | 16.0 | 8.5 | -12.0 | 1.8 | 14.3 | 13.0 | 10.9 | 2.8 | 9.4 | -19.0 | 2.2 |
| 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 |
| Value | 34 | 514 | -117.0 | -78.0 | -79.0 | 107 | -134.0 | -76.0 | -199.0 | -59.0 | -148.0 | -83.0 | -100.0 | -74.0 | -170.0 | -104.0 |
| Percentage of NetCashProvidedByUsedInInvestingActivities | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 1.2 | 17.9 | -4.9 | -3.3 | -3.7 | 4.5 | -5.5 | -3.0 | -7.3 | -2.2 | -4.4 | -2.4 | -2.8 | -2.4 | -5.4 | -3.5 |
| 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 |
| Value | -849.0 | 428 | -63.0 | 692 | -71.0 | -44.0 | -93.0 | -81.0 | -71.0 | -199.0 | -294.0 | -280.0 | 433 | -147.0 | -53.0 | -115.0 |
| Percentage of NetCashProvidedByUsedInFinancingActivities | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | -30.0 | 14.9 | -2.6 | 29.3 | -3.3 | -1.8 | -3.8 | -3.2 | -2.6 | -7.3 | -8.8 | -8.3 | 12.1 | -4.8 | -1.7 | -3.9 |
| 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 | -892.0 | 937 | -129.0 | 771 | 136 | -51.0 | 39 | 7.0 | -183.0 | -96.0 | 90 | -69.0 | -108.0 | -162.0 | 238 | 162 | 143 | -37.0 |
| Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | -31.5 | 32.6 | -5.4 | 32.6 | 6.3 | -2.1 | 1.6 | 0.3 | -6.8 | -3.5 | 2.7 | -2.0 | -3.0 | -5.2 | 7.5 | 5.5 | 5.0 | -1.4 |
| 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 | 2015-12-31 |
| Value | 30 | 18 | -14.0 | -6.0 | -29.0 | 23 | -44.0 | -5.0 | 31 | 33 | -20.0 | 15 | -20.0 | -11.0 | 112 | 14 | 27 | 23 | -52.0 | 34 | 103 |
| Percentage of DeferredIncomeTaxExpenseBenefit | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 161 | 182 | 170 | 161 | 152 | 170 | 183 | 184 | 174 | 172 | 174 | 173 | 192 | 194 | 187 | 194 | 190 | 179 | 182 | 181 | 178 | 177 | 186 | 190 |
| Percentage of DepreciationDepletionAndAmortization | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 116 | 68 | 99 | -37.0 | -143.0 | -41.0 | -26.0 | -58.0 | -36.0 | -17.0 | -1.0 | 12 | 98 | 169 | 136 | 16 | -16.0 | 102 | 24 | 17 | -34.0 | -8.0 | -120.0 |
| Percentage of IncreaseDecreaseInInventories | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -86.0 | 6.0 | 38 | 158 | 288 | -90.0 | 262 | 174 | 82 | 168 | 535 | 288 | -430.0 | 55 | 455 | 384 | 311 | 74 | 239 | -359.0 | 53 |
| Percentage of NetCashProvidedByUsedInOperatingActivities | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | -3.0 | 0.2 | 1.6 | 6.7 | 13.4 | -3.8 | 10.8 | 6.8 | 3.0 | 6.2 | 16.0 | 8.5 | -12.0 | 1.8 | 14.3 | 13.0 | 10.9 | 2.8 | 9.4 | -19.0 | 2.2 |
| 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 |
| Value | 309 | 175 | -4.0 | -49.0 | -197.0 | 80 | -303.0 | -221.0 | -402.0 | -199.0 | 43 | -41.0 | 75 | 150 | -196.0 | 113 | 75 | 225 | -125.0 | -6.0 | -55.0 | -210.0 | -826.0 | -124.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 10.9 | 6.1 | -0.2 | -2.1 | -9.2 | 3.4 | -12.4 | -8.6 | -14.8 | -7.3 | 1.3 | -1.2 | 2.1 | 4.9 | -6.2 | 3.8 | 2.6 | 8.5 | -4.9 | -0.3 | -2.7 | -11.1 | -33.7 | -4.6 |
| 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 | 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 |
| Value | 350 | 219 | 17 | -20.0 | -150.0 | 139 | -355.0 | -147.0 | -293.0 | -58.0 | 212 | 155 | 230 | 274 | -56.0 | 169 | 138 | 308 | -129.0 | 14 | -12.0 | -215.0 | -890.0 | -63.0 |
| 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 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 12.4 | 7.6 | 0.7 | -0.8 | -7.0 | 5.8 | -14.6 | -5.7 | -10.8 | -2.1 | 6.3 | 4.6 | 6.4 | 8.9 | -1.8 | 5.7 | 4.8 | 11.6 | -5.1 | 0.6 | -0.6 | -11.4 | -36.3 | -2.4 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 27 | 25 | 28 | 20 | 27 | 23 | 26 |
| Percentage of ProfitLoss | 7.7 | 11.4 | -140.0 | -13.3 | 19.4 | -15.6 | -8.9 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.0 | 0.9 | 1.2 | 0.9 | 1.1 | 0.9 | 1.0 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Energy us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 25 | -5.0 | 16 | -5.0 | 9.0 | 23 | 2.0 |
| Percentage of ProfitLoss | 7.1 | -2.3 | -80.0 | 3.3 | 6.5 | -15.6 | -0.7 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 0.9 | -0.2 | 0.7 | -0.2 | 0.4 | 0.9 | 0.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:Mining us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 |
| Value | -4.0 | -2.0 | -10.0 | -6.0 | -9.0 | -15.0 |
| Percentage of ProfitLoss | -1.1 | -0.9 | 50.0 | 4.0 | -6.5 | 10.2 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | -0.1 | -0.1 | -0.4 | -0.3 | -0.4 | -0.6 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:OtherProducts us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | 102 | 45 | -38.0 | -75.0 | -13.0 | -27.0 | -57.0 |
| Percentage of ProfitLoss | 29.1 | 20.5 | 190.0 | 50.0 | -9.4 | 18.4 | 19.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 3.6 | 1.6 | -1.6 | -3.5 | -0.5 | -1.1 | -2.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax aa:MaadenJointVenture us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees | 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 |
| Value | 41 | 44 | 21 | 29 | 47 | 59 | -52.0 | 74 | 109 | 141 | 169 | 196 | 155 | 124 | 140 | 56 | 63 | 83 | -4.0 | 20 | 43 | -5.0 | -64.0 | 61 |
| Percentage of ProfitLoss | 11.7 | 20.1 | 123.5 | -145.0 | -31.3 | 42.4 | 14.6 | -50.3 | -37.2 | -243.1 | 79.7 | 126.5 | 67.4 | 45.3 | -250.0 | 33.1 | 45.7 | 26.9 | 3.1 | 142.9 | -358.3 | 2.3 | 7.2 | -96.8 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 1.4 | 1.5 | 0.9 | 1.2 | 2.2 | 2.5 | -2.1 | 2.9 | 4.0 | 5.2 | 5.1 | 5.8 | 4.3 | 4.0 | 4.4 | 1.9 | 2.2 | 3.1 | -0.2 | 0.9 | 2.1 | -0.3 | -2.6 | 2.3 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:NoncontrollingInterest | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 | 309 | 175 | -4.0 | -49.0 | -197.0 | 80 | -303.0 | -221.0 | -402.0 | -199.0 | 43 | -41.0 | 75 | 150 | -196.0 | 113 | 75 | 225 |
| Percentage of ProfitLoss | 88.3 | 79.9 | -23.5 | 245.0 | 131.3 | 57.6 | 85.4 | 150.3 | 137.2 | 343.1 | 20.3 | -26.5 | 32.6 | 54.7 | 350.0 | 66.9 | 54.3 | 73.1 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax | 10.9 | 6.1 | -0.2 | -2.1 | -9.2 | 3.4 | -12.4 | -8.6 | -14.8 | -7.3 | 1.3 | -1.2 | 2.1 | 4.9 | -6.2 | 3.8 | 2.6 | 8.5 |
| Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 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 |
| Value | 10.0 | 8.0 | 1.0 | 7.0 | 9.0 | 8.0 | 1.0 | 8.0 | 11 | 10.0 | 6.0 | 9.0 | 10.0 | 10.0 | 3.0 | 7.0 | 7.0 | 7.0 | 4.0 | 6.0 | 10.0 | 8.0 | 4.0 |
| Percentage of ShareBasedCompensation | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 34 | 514 | -117.0 | -78.0 | -79.0 | 107 | -134.0 | -76.0 | -199.0 | -59.0 | -148.0 | -83.0 | -100.0 | -74.0 | -170.0 | -104.0 |
| Percentage of NetCashProvidedByUsedInInvestingActivities | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | 1.2 | 17.9 | -4.9 | -3.3 | -3.7 | 4.5 | -5.5 | -3.0 | -7.3 | -2.2 | -4.4 | -2.4 | -2.8 | -2.4 | -5.4 | -3.5 |
| 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 | 79 | 75 | 111 | 74 | 77 | 91 | 134 | 87 | 89 | 69 | 148 | 82 | 95 | 74 | 150 | 96 | 88 | 71 | 146 | 86 | 86 | 86 | 133 |
| Percentage of PaymentsToAcquirePropertyPlantAndEquipment | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 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 | 1.0 | 2.0 | 6.0 | 3.0 | 2.0 | 1.0 | 0.0 | 1.0 | 110 | 1.0 | 1.0 | 1.0 | 22 | 8.0 | 11 | 25 | 0.0 | 0.0 | 0.0 | 3.0 | 27 |
| Percentage of PaymentsToAcquireInvestments | 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 | 0.0 | 0.0 | 0.0 | 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 |
| Value | -849.0 | 428 | -63.0 | 692 | -71.0 | -44.0 | -93.0 | -81.0 | -71.0 | -199.0 | -294.0 | -280.0 | 433 | -147.0 | -53.0 | -115.0 |
| Percentage of NetCashProvidedByUsedInFinancingActivities | 100.0 | 100.0 | 100.0 | 100.0 | 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 RevenueFromContractWithCustomerExcludingAssessedTax | -30.0 | 14.9 | -2.6 | 29.3 | -3.3 | -1.8 | -3.8 | -3.2 | -2.6 | -7.3 | -8.8 | -8.3 | 12.1 | -4.8 | -1.7 | -3.9 |
| Period End | 2020-07-31 |
| Value | 736 |
| Percentage of ProceedsFromIssuanceOfLongTermDebt | 100.0 |
| Period End | 2021-03-31 |
| Value | 493 |
| Percentage of ProceedsFromIssuanceOfLongTermDebt | 0.0 |
| Period End | 2021-03-31 |
| Value | 5.5 |
| Percentage of DebtInstrumentInterestRateStatedPercentage | 100.0 |
| Percentage of LongTermDebtAndCapitalLeaseObligations | 0.0 |
| Percentage of LongTermDebtAndCapitalLeaseObligations us-gaap:RevolvingCreditFacility aa:FivePointFiveZeroZeroPercentageSeniorNotesDueTwoThousandAndTwentySeven | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2016-10-31 |
| Value | 26.85 | 28.38 | 28.41 | 25.48 | 24.69 | 24.42 |
| Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | 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 | 2015-12-31 |
| Value | 1041 | 1010 | 872 | 1185 | 1333 | 1615 |
| Percentage of DeferredTaxAssetsNet | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 32 | 14 | 98 | 89 |
| Percentage of DeferredTaxAssetsNet | 3.1 | 1.4 | 8.3 | 6.7 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 401 | 625 | 605 | 587 | 701 |
| Percentage of DeferredTaxAssetsNet | 38.5 | 61.9 | 69.4 | 49.5 | 52.6 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 608 | 371 | 267 | 500 | 510 |
| Percentage of DeferredTaxAssetsNet | 58.4 | 36.7 | 30.6 | 42.2 | 38.3 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 | 2014-12-31 | 2013-12-31 |
| Value | 4.0 | 29 | 30 | 10.0 | 22 | 22 | 25 | 52 |
| Percentage of UnrecognizedTaxBenefits | 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 | 2015-12-31 | 2014-12-31 | 2013-12-31 |
| Value | 2127 | 1778 | 1684 | 1927 | 1755 | 712 | 486 | 517 |
| Percentage of DeferredTaxAssetsValuationAllowance | 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 | 1185 | 898 | 779 | 1050 | 1057 |
| Percentage of DeferredTaxAssetsValuationAllowance | 55.7 | 50.5 | 46.3 | 54.5 | 60.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 942 | 880 | 905 | 877 | 698 |
| Percentage of DeferredTaxAssetsValuationAllowance | 44.3 | 49.5 | 53.7 | 45.5 | 39.8 |
| Period End | 2020-12-31 | 2018-12-31 |
| Value | 58 | 86 |
| Percentage of DeferredTaxAssetsValuationAllowance | 2.7 | 5.1 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 359 | 318 | 263 | 152 | 88 |
| Percentage of DeferredTaxAssetsValuationAllowance | 16.9 | 17.9 | 15.6 | 7.9 | 5.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 301 | 350 | 325 | 523 | 272 |
| Percentage of DeferredTaxAssetsValuationAllowance | 14.2 | 19.7 | 19.3 | 27.1 | 15.5 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 822 | 300 | 370 | 315 | 265 |
| Percentage of DeferredTaxAssetsValuationAllowance | 38.6 | 16.9 | 22.0 | 16.3 | 15.1 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 645 | 810 | 726 | 937 | 1130 |
| Percentage of DeferredTaxAssetsValuationAllowance | 30.3 | 45.6 | 43.1 | 48.6 | 64.4 |
| Period End | 2021-03-31 | 2020-12-31 | 2019-03-31 |
| Value | -3.0 | 5.0 | -1.0 |
| Percentage of AccrualForEnvironmentalLossContingenciesForeignCurrencyTranslationGainLossAndOther | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | -6.0 | 72 |
| Percentage of AccruedOtherPostretirementBenefitAdditionToRemeasurement | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 0.0 | 495 | 0.0 |
| Percentage of AdditionsToLongTermDebtIssuedLessIssuanceDiscount | 0.0 | 100.0 | 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 | 625 | 569 | 398 | 359 | 185 | 375 | 340 | 400 | 484 | 402 | 740 | 839 | 969 | 655 | 902 | 619 | 546 | 613 | 425 | 358 | 393 | 257 |
| Percentage of AdjustedEbitda | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 124 | 227 | 97 | 119 | 88 | 193 | 133 | 223 | 369 | 372 | 683 | 660 | 638 | 392 | 562 | 203 | 227 | 297 | 171 | 78 | 114 | 15 |
| Percentage of AdjustedEbitda | 19.8 | 39.9 | 24.4 | 33.1 | 47.6 | 51.5 | 39.1 | 55.8 | 76.2 | 92.5 | 92.3 | 78.7 | 65.8 | 59.8 | 62.3 | 32.8 | 41.6 | 48.5 | 40.2 | 21.8 | 29.0 | 5.8 |
| 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 |
| Value | 460 | 283 | 181 | 116 | -34.0 | 62 | 75 | 43 | 3.0 | -96.0 | -53.0 | 73 | 231 | 153 | 234 | 303 | 221 | 206 | 152 | 183 | 180 | 165 |
| Percentage of AdjustedEbitda | 73.6 | 49.7 | 45.5 | 32.3 | -18.4 | 16.5 | 22.1 | 10.8 | 0.6 | -23.9 | -7.2 | 8.7 | 23.8 | 23.4 | 25.9 | 48.9 | 40.5 | 33.6 | 35.8 | 51.1 | 45.8 | 64.2 |
| 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 |
| Value | 41 | 59 | 120 | 124 | 131 | 120 | 132 | 134 | 112 | 126 | 110 | 106 | 100 | 110 | 106 | 113 | 98 | 110 | 102 | 97 | 99 | 77 |
| Percentage of AdjustedEbitda | 6.6 | 10.4 | 30.2 | 34.5 | 70.8 | 32.0 | 38.8 | 33.5 | 23.1 | 31.3 | 14.9 | 12.6 | 10.3 | 16.8 | 11.8 | 18.3 | 17.9 | 17.9 | 24.0 | 27.1 | 25.2 | 30.0 |
| 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 |
| Value | 2372 | 2558 | 2355 | 2343 | 2253 | 2162 | 2737 | 2619 | 2888 | 2627 | 2975 | 2984 | 3169 | 2678 | 2958 | 2676 | 2622 | 2237 | 2660 | 2227 | 2267 |
| Percentage of CostsAndOperatingExpensesAndNonoperatingIncomeExpenses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2020-10-31 |
| Value | 228000.0 |
| Percentage of CurtailmentOfSmeltingCapacity | 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 |
| Value | 12 | 12 | 35 | 36 | 34 | 33 | 29 | 30 | 30 | 30 | 31 | 34 | 41 | 40 | 28 | 28 | 27 | 28 | 23 | 20 | 12 | 11 | 14 |
| Percentage of DefinedBenefitPensionPlansNetPeriodicBenefitCost | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 0 |
| Percentage of DefinedBenefitPlanEmployersContributionPercentageOnAnnualBasis | 0.0 |
| Period End | 2020-09-30 |
| Value | 685.0 |
| Percentage of DefinedBenefitPlanNumberOfEmployeesReduced | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0 | -1000000.0 | -2000000.0 | 0 | 1000000.0 |
| Percentage of DiscreteTaxBenefitExpense | 0.0 | 100.0 | 100.0 | 0.0 | 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 |
| Value | -11.2 | 39.2 | 138.23 | -2.401 | 0.571 | -8.233 | 1.371 | 0.722 | 0.035 |
| Percentage of EstimatedAnnualizedEffectiveTaxRate | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 |
| Value | 3000000.0 |
| Percentage of FairValueAssetsMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet | 100.0 |
| Period End | 2020-09-30 |
| Value | 4.0 |
| Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeExpensesNet | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 1000000.0 | -5000000.0 |
| Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet | 100.0 | 100.0 |
| Period End | 2021-06-30 |
| Value | -1000000.0 |
| Percentage of FairValueLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInOtherIncomeNet | -100.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 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 |
| Value | 0.0 | 1.0 | 2.0 | 0.0 | 1.0 | 2.0 | 1.0 | -3.0 | -4.0 | -5.0 | -2.0 | 5.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetIncreaseDecreaseOther | 0.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 7000000.0 | -15000000.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesGainLossIncludedInCostOfGoodsSold | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 |
| Value | 1.0 | -1.0 | -2.0 | 1.0 | 2.0 | 1.0 | 0.0 | 0.0 | 0.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 0.0 | -2.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther | 0.0 | 200.0 |
| Period End | 2020-09-30 | 2020-06-30 |
| Value | -2.0 | -1.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitiesIncreaseDecreaseOther | -200.0 | -50.0 |
| Period End | 2020-10-08 |
| Value | 228000.0 |
| Percentage of FullCurtailmentOfSmeltingCapacity | 100.0 |
| Period End | 2021-06-30 |
| Value | 89 |
| Percentage of GainLossOnDispositionOfAssetsAfterTax | 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 |
| Value | -11.0 | -10.0 | -2.0 | -11.0 | -7.0 | -11.0 | -12.0 | -9.0 | -10.0 | -11.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments | 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 |
| Value | -9.0 | -1.0 | -9.0 | -5.0 | -3.0 | -6.0 | -1.0 | -7.0 | -3.0 | -5.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments | 81.8 | 10.0 | 450.0 | 45.5 | 42.9 | 54.5 | 8.3 | 77.8 | 30.0 | 45.5 |
| 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 |
| Value | 2.0 | 1.0 | 0.0 | 4.0 | 3.0 | 4.0 | 3.0 | 7.0 | 0.0 | 3.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments | -18.2 | -10.0 | -0.0 | -36.4 | -42.9 | -36.4 | -25.0 | -77.8 | -0.0 | -27.3 |
| 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 |
| Value | -26.0 | -11.0 | -5.0 | 10.0 | 19 | 3.0 | 12 | 7.0 | 14 | 17 |
| Percentage of IncomeLossFromEquityMethodInvestmentsBeforeReconcilingAdjustments | 236.4 | 110.0 | 250.0 | -90.9 | -271.4 | -27.3 | -100.0 | -77.8 | -140.0 | -154.5 |
| 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 |
| Value | 26 | 5.0 | -3.0 | -14.0 | -22.0 | -7.0 | -15.0 | -7.0 | -15.0 | -12.0 | -19.0 | 1.0 | 3.0 | -2.0 | 51 | -13.0 | -3.0 | -7.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsNonoperating | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 |
| Value | -1.0 | -1.0 | 2.0 | 1.0 | -1.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 |
| Value | 1.0 | 0.0 | 0.0 | -2.0 | 3.0 | 1.0 | 0.0 | 2.0 | -8.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments | 0.0 | 0.0 | -0.0 | 200.0 | 150.0 | 0.0 | 0.0 | -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 |
| Value | -8.0 | -3.0 | -1.0 | -3.0 | -5.0 | -5.0 | -6.0 | -8.0 | 0.0 | -2.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments | 0.0 | 0.0 | 0.0 | 300.0 | 500.0 | -250.0 | 0.0 | -800.0 | -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 |
| Value | 0.0 | 4.0 | 2.0 | 1.0 | 1.0 | 3.0 | 2.0 | -1.0 | 2.0 | -6.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsReconcilingAdjustments | 0.0 | 0.0 | 0.0 | -100.0 | -100.0 | 150.0 | 0.0 | -100.0 | -200.0 | 0.0 |
| Period End | 2020-12-31 |
| Value | 32 |
| Percentage of IncomeTaxExaminationReversalOfProvisionForIncomeTaxesReserve | 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 |
| Value | 95 | 122 | 394 | -334.0 | 125 | 1058 | -183.0 | 67 |
| Percentage of IncomeTaxExpenseBenefitFromEstimatedAnnualizedEffectiveTaxRate | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 |
| Value | -6000000.0 |
| Percentage of IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities | 100.0 |
| Period End | 2021-06-30 |
| Value | -6000000.0 |
| Percentage of IncreaseDecreaseInDisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilities | 100.0 |
| Period End | 2020-07-07 |
| Value | 1000000.0 |
| Percentage of IncreaseInIncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority | 100.0 |
| Period End | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 135 | 20 | 0.0 | 75 |
| Percentage of MinimumRequiredCashContributionToPensionPlan | 100.0 | 100.0 | 0.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2020-01-31 |
| Value | 54 | 49 | 9.0 | 0.0 | 40 | 40 |
| Percentage of MinimumRequiredCashContributionToPensionPlan | 0.0 | 36.3 | 45.0 | 0.0 | 53.3 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 |
| Value | 6.0 | 14 | 15 |
| Percentage of MinimumRequiredCashContributionToPensionPlan | 0.0 | 10.4 | 75.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 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 | 0.0 | 8.0 | 16 | 10.0 | 20 | 1.0 | 20 | 40 | 0.0 | 56 | 53 | 24 | 0.0 | 32 | 24 |
| Percentage of MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 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 | 0.0 | 8.0 | 16 | 10.0 | 20 | 1.0 | 20 | 40 | 0.0 | 56 | 53 | 24 | 0.0 | 32 | 24 |
| Percentage of MinorityInterestIncreaseDecreaseFromCapitalContributionFromNoncontrollingInterestHolders | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 |
| Period End | 2020-09-30 |
| Value | 50.0 |
| Percentage of PaymentAmountRefundPercentage | 100.0 |
| Period End | 2020-12-31 | 2020-09-30 |
| Value | 4000000.0 | 1000000.0 |
| Percentage of PaymentOfContractTerminationCost | 100.0 | 100.0 |
| Period End | 2020-09-30 |
| Value | 50.0 |
| Percentage of PaymentOfDisputedTaxAmountPercentage | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 7.0 | 6.0 | 8.0 | 6.0 | 12 | 12 |
| Percentage of PaymentsForFinancialContributionsForTheDivestitureOfBusinesses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-09-17 |
| Value | 91 |
| Percentage of ProposedAdministrativePenalties | 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 |
| Value | 33 | 7.0 | 60 | 5.0 | 37 | 2.0 | 363 | 185 | 370 | 113 | 138 | 177 | 231 |
| Percentage of RestructuringAndOtherCharges | 100.0 | 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 |
| Value | 30 | -8.0 | 47 | 0.0 | 0.0 | -2.0 | 103 | 18 | 18 | 4.0 | 13 | 173 | 149 |
| Percentage of RestructuringAndOtherCharges | 90.9 | -114.3 | 78.3 | 0.0 | 0.0 | -100.0 | 28.4 | 9.7 | 4.9 | 3.5 | 9.4 | 97.7 | 64.5 |
| 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 |
| Value | 33 | 7.0 | 60 | 5.0 | 37 | 2.0 | 363 | 185 | 370 | 113 | 138 | 177 |
| Percentage of RestructuringAndOtherCharges | 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 |
| Value | 3.0 | 15 | 13 | 5.0 | 37 | 4.0 | 260 | 167 | 352 | 109 | 125 | 4.0 | 82 |
| Percentage of RestructuringAndOtherCharges | 9.1 | 214.3 | 21.7 | 100.0 | 100.0 | 200.0 | 71.6 | 90.3 | 95.1 | 96.5 | 90.6 | 2.3 | 35.5 |
| 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 |
| Value | 0.0 | 3.0 | 0.0 | 2.0 | 256 | 15 | 0.0 | 1.0 | 109 | 1.0 | 3.0 |
| Percentage of RestructuringAndOtherCharges | 0.0 | 60.0 | 0.0 | 100.0 | 70.5 | 8.1 | 0.0 | 0.9 | 79.0 | 0.6 | 1.3 |
| 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 |
| Value | 3.0 | 15 | 13 | 1.0 | 37 | 2.0 | 4.0 | 147 | 353 | 107 | 16 | 2.0 | 79 |
| Percentage of RestructuringAndOtherCharges | 9.1 | 214.3 | 21.7 | 20.0 | 100.0 | 100.0 | 1.1 | 79.5 | 95.4 | 94.7 | 11.6 | 1.1 | 34.2 |
| Period End | 2020-12-31 | 2020-09-30 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 |
| Value | 0.0 | 1.0 | 0.0 | 5.0 | -1.0 | 1.0 | 0.0 | 1.0 |
| Percentage of RestructuringAndOtherCharges | 0.0 | 20.0 | 0.0 | 2.7 | -0.3 | 0.9 | 0.0 | 0.6 |
| Period End | 2021-07-28 |
| Value | 30 |
| Percentage of RestructuringAndOtherCharges | 0.0 |
| Period End | 2021-07-28 |
| Value | 25 |
| Percentage of RestructuringAndOtherCharges | 0.0 |
| Period End | 2020-12-31 |
| Value | 40 |
| Percentage of RestructuringAndOtherCharges | 66.7 |
| Period End | 2020-12-31 |
| Value | 35 |
| Percentage of RestructuringAndOtherCharges | 58.3 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 3.0 | 6.0 |
| Percentage of RestructuringAndOtherCharges | 9.1 | 85.7 |
| Period End | 2020-09-30 | 2020-06-30 |
| Value | 4.0 | 11 |
| Percentage of RestructuringAndOtherCharges | 80.0 | 29.7 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 1.0 | 4.0 |
| Percentage of RestructuringAndOtherCharges | 3.0 | 57.1 |
| Period End | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 |
| Value | 0.0 | 1.0 | 1.0 | 37 |
| Percentage of RestructuringAndOtherCharges | 0.0 | 2.7 | 50.0 | 20.0 |
| Period End | 2021-06-30 |
| Value | 39 |
| Percentage of RestructuringAndOtherCharges | 118.2 |
| Period End | 2020-10-31 |
| Value | 40 |
| Percentage of RestructuringAndOtherChargesEstimatedButNotIncurred | 100.0 |
| Period End | 2020-10-31 |
| Value | 35 |
| Percentage of RestructuringAndOtherChargesEstimatedButNotIncurred | 87.5 |
| 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 |
| Value | 4.0 | 6.0 | 8.0 | 1.0 | 39 | 4.0 | 0.0 | 165 | 17 | 30 |
| Percentage of RestructuringAndOtherChargesNet | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 4.0 | 6.0 | 8.0 | 4.0 | 21 | 3.0 | 1.0 | 121 | 11 | 28 |
| Percentage of RestructuringAndOtherChargesNet | 100.0 | 100.0 | 100.0 | 400.0 | 53.8 | 75.0 | 0.0 | 73.3 | 64.7 | 93.3 |
| 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 |
| Value | 0.0 | -3.0 | 18 | 1.0 | -1.0 | 44 | 6.0 | 2.0 |
| Percentage of RestructuringAndOtherChargesNet | 0.0 | -300.0 | 46.2 | 25.0 | 0.0 | 26.7 | 35.3 | 6.7 |
| 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 | 28 | 26 | 30 | 24 | 21 | 27 | 22 | 27 | 28 | 24 | 21 | 22 | 26 | 27 | 32 | 34 | 36 | 33 | 44 | 47 | 50 | 36 |
| Percentage of SegmentReportingInformationCorporateExpenses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 155 | 176 | 165 | 154 | 146 | 164 | 171 | 177 | 167 | 165 | 164 | 166 | 184 | 188 | 177 | 183 | 180 | 168 | 167 | 171 | 170 | 165 | 176 | 179 |
| Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 50 | 46 | 45 | 41 | 37 | 49 | 57 | 54 | 55 | 48 | 47 | 48 | 49 | 53 | 52 | 53 | 53 | 49 | 43 | 48 | 47 | 45 | 47 | 48 |
| Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses | 32.3 | 26.1 | 27.3 | 26.6 | 25.3 | 29.9 | 33.3 | 30.5 | 32.9 | 29.1 | 28.7 | 28.9 | 26.6 | 28.2 | 29.4 | 29.0 | 29.4 | 29.2 | 25.7 | 28.1 | 27.6 | 27.3 | 26.7 | 26.8 |
| 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 |
| Value | 73 | 73 | 82 | 80 | 79 | 81 | 84 | 88 | 85 | 89 | 89 | 91 | 108 | 106 | 104 | 106 | 108 | 101 | 73 | 72 | 104 | 103 | 77 | 77 |
| Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses | 47.1 | 41.5 | 49.7 | 51.9 | 54.1 | 49.4 | 49.1 | 49.7 | 50.9 | 53.9 | 54.3 | 54.8 | 58.7 | 56.4 | 58.8 | 57.9 | 60.0 | 60.1 | 43.7 | 42.1 | 61.2 | 62.4 | 43.8 | 43.0 |
| 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 |
| Value | 32 | 57 | 38 | 33 | 30 | 34 | 30 | 35 | 27 | 28 | 28 | 27 | 27 | 29 | 21 | 24 | 19 | 18 | 20 | 21 | 19 | 17 | 21 | 23 |
| Percentage of SegmentReportingInformationDepreciationDepletionAndAmortizationExpenses | 20.6 | 32.4 | 23.0 | 21.4 | 20.5 | 20.7 | 17.5 | 19.8 | 16.2 | 17.0 | 17.1 | 16.3 | 14.7 | 15.4 | 11.9 | 13.1 | 10.6 | 10.7 | 12.0 | 12.3 | 11.2 | 10.3 | 11.9 | 12.8 |
| 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 |
| Value | 27 | 8.0 | 4.0 | -10.0 | -20.0 | -4.0 | -14.0 | -5.0 | -14.0 | -10.0 | -16.0 | 5.0 | 6.0 | -1.0 | -3.0 | -12.0 | -3.0 | -6.0 | -10.0 | -16.0 | -17.0 | -21.0 | -19.0 | -24.0 |
| Percentage of SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -1.0 | -5.0 | -2.0 | -4.0 | -8.0 | -9.0 | -9.0 | 0.0 | 3.0 | 12 | 9.0 | 10.0 | 14 | -1.0 | 5.0 | -5.0 | -6.0 | 1.0 | -10.0 | -9.0 | -7.0 | -14.0 | -14.0 | -9.0 |
| Percentage of SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments | -3.7 | -62.5 | -50.0 | 40.0 | 40.0 | 225.0 | 64.3 | -0.0 | -21.4 | -120.0 | -56.2 | 200.0 | 233.3 | 100.0 | -166.7 | 41.7 | 200.0 | -16.7 | 100.0 | 56.2 | 41.2 | 66.7 | 73.7 | 37.5 |
| 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 | 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 |
| Value | 28 | 13 | 6.0 | -6.0 | -12.0 | 5.0 | -5.0 | -5.0 | -17.0 | -22.0 | -25.0 | -5.0 | -8.0 | -8.0 | -7.0 | 3.0 | -7.0 | 11 | 5.0 | -10.0 | -7.0 | 4.0 | -2.0 |
| Percentage of SegmentReportingInformationEquityInNetIncomeOfEquityMethodInvesteesOfSegments | 103.7 | 162.5 | 150.0 | 60.0 | 60.0 | -125.0 | 35.7 | 100.0 | 121.4 | 220.0 | 156.2 | -100.0 | -133.3 | 266.7 | 58.3 | -100.0 | 116.7 | -110.0 | -31.2 | 58.8 | 33.3 | -21.1 | 8.3 |
| 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 |
| Value | 35 | -7.0 | 5.0 | -35.0 | 30 | -8.0 | 40 | 25 | -1.0 | 86 | 47 | 21 | -152.0 | 76 |
| Percentage of SegmentReportingInformationIntersegmentEliminations | 100.0 | 100.0 | 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 |
| Value | 525 | 551 | 544 | 567 | 536 | 574 | 582 | 624 | 695 | 656 | 816 | 774 | 766 | 707 | 812 | 628 | 595 | 584 | 1686 | 1559 | 505 | 501 | 1771 | 1922 |
| Percentage of SegmentReportingInformationIntersegmentRevenues | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 343 | 364 | 314 | 329 | 289 | 336 | 330 | 369 | 445 | 417 | 567 | 544 | 536 | 454 | 580 | 398 | 384 | 361 | 377 | 317 | 321 | 292 | 357 | 396 |
| Percentage of SegmentReportingInformationIntersegmentRevenues | 65.3 | 66.1 | 57.7 | 58.0 | 53.9 | 58.5 | 56.7 | 59.1 | 64.0 | 63.6 | 69.5 | 70.3 | 70.0 | 64.2 | 71.4 | 63.4 | 64.5 | 61.8 | 22.4 | 20.3 | 63.6 | 58.3 | 20.2 | 20.6 |
| 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 | 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 |
| Value | 3.0 | 2.0 | 5.0 | 2.0 | 2.0 | 3.0 | 6.0 | 4.0 | 4.0 | 3.0 | 4.0 | 6.0 | 4.0 | 4.0 | 5.0 | 9.0 | 3.0 | 4.0 | 947 | 918 | 2.0 | 34 | 1052 | 1132 |
| Percentage of SegmentReportingInformationIntersegmentRevenues | 0.6 | 0.4 | 0.9 | 0.4 | 0.4 | 0.5 | 1.0 | 0.6 | 0.6 | 0.5 | 0.5 | 0.8 | 0.5 | 0.6 | 0.6 | 1.4 | 0.5 | 0.7 | 56.2 | 58.9 | 0.4 | 6.8 | 59.4 | 58.9 |
| 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 |
| Value | 179 | 185 | 225 | 236 | 245 | 235 | 246 | 251 | 246 | 236 | 245 | 224 | 226 | 249 | 227 | 221 | 208 | 219 | 202 | 192 | 182 | 175 | 285 | 305 |
| Percentage of SegmentReportingInformationIntersegmentRevenues | 34.1 | 33.6 | 41.4 | 41.6 | 45.7 | 40.9 | 42.3 | 40.2 | 35.4 | 36.0 | 30.0 | 28.9 | 29.5 | 35.2 | 28.0 | 35.2 | 35.0 | 37.5 | 12.0 | 12.3 | 36.0 | 34.9 | 16.1 | 15.9 |
| 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 |
| Value | 2.0 | 6.0 | 11 | 15 | 17 | 35 | 32 | 18 | 11 | 18 | 3.0 | 10.0 | 36 | 23 | 83 | 51 | 43 | 39 | 23 | -56.0 | 59 | 74 | 142 | 53 |
| Percentage of SegmentReportingInformationOtherIncomeExpenseNet | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 13 | 11 | 8.0 | 11 | 10.0 | 16 | 6.0 | 6.0 | -3.0 | -2.0 | 1.0 | -1.0 | 1.0 | 2.0 | -10.0 | 11 | 28 | 20 |
| Percentage of SegmentReportingInformationTransformation | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 2829 | 2865 | 2384 | 2360 | 2144 | 2376 | 2417 | 2548 | 2688 | 2697 | 3319 | 3366 | 3558 | 3072 | 2936 | 2668 | 2608 | 2417 | 2292 | 2032 | 2023 | 1855 | 2215 | 2395 |
| Percentage of SegmentReportingInformationUnrelatedPartySales | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 688 | 760 | 620 | 697 | 603 | 707 | 718 | 771 | 864 | 897 | 1132 | 1101 | 1068 | 914 | 937 | 713 | 749 | 734 | 618 | 585 | 601 | 496 | 707 | 878 |
| Percentage of SegmentReportingInformationUnrelatedPartySales | 24.3 | 26.5 | 26.0 | 29.5 | 28.1 | 29.8 | 29.7 | 30.3 | 32.1 | 33.3 | 34.1 | 32.7 | 30.0 | 29.8 | 31.9 | 26.7 | 28.7 | 30.4 | 27.0 | 28.8 | 29.7 | 26.7 | 31.9 | 36.7 |
| 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 |
| Value | 2102 | 2047 | 1685 | 1607 | 1475 | 1598 | 1634 | 1677 | 1757 | 1735 | 2107 | 2198 | 2413 | 2111 | 1920 | 1851 | 1779 | 1613 | -6.0 | 1346 | 1335 | 1315 | 10.0 | 2.0 |
| Percentage of SegmentReportingInformationUnrelatedPartySales | 74.3 | 71.4 | 70.7 | 68.1 | 68.8 | 67.3 | 67.6 | 65.8 | 65.4 | 64.3 | 63.5 | 65.3 | 67.8 | 68.7 | 65.4 | 69.4 | 68.2 | 66.7 | -0.3 | 66.2 | 66.0 | 70.9 | 0.5 | 0.1 |
| 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 |
| Value | 39 | 58 | 79 | 56 | 66 | 71 | 65 | 100 | 67 | 65 | 80 | 67 | 77 | 47 | 79 | 104 | 80 | 70 | 91 | 93 | 87 | 44 | 16 | 26 |
| Percentage of SegmentReportingInformationUnrelatedPartySales | 1.4 | 2.0 | 3.3 | 2.4 | 3.1 | 3.0 | 2.7 | 3.9 | 2.5 | 2.4 | 2.4 | 2.0 | 2.2 | 1.5 | 2.7 | 3.9 | 3.1 | 2.9 | 4.0 | 4.6 | 4.3 | 2.4 | 0.7 | 1.1 |
| 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 |
| Value | 16 | -28.0 | -350.0 | 379 | -46.0 | -971.0 | 298 | 83 | 9.0 |
| Percentage of UnfavorableFavorableImpactIncomeTaxExpenseBenefit | 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 |
| Value | 8.44 | 35.67 | 0.35 | 26.5 | 26.45 | 26.55 | -0.16 | 32.82 | 33.77 | 38.49 |
| Percentage of WeightedAverageExercisePriceOfUnderwaterOptions | 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 |
| Value | 0.0 | 4.0 | 1.0 | 4.0 | 0.0 | 2.0 | 69 | 2.0 | 1.0 | 1.0 |
| Percentage of AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 |
| Value | -10000000.0 | -7000000.0 | 0 | 0 | 0 | -1000000.0 |
| Percentage of AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates | 100.0 | 100.0 | 0.0 | 0.0 | 0.0 | 100.0 |
| Period End | 2021-06-30 |
| Value | -5000000.0 |
| Percentage of AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates | 50.0 |
| Period End | 2021-06-30 |
| Value | -5000000.0 |
| Percentage of AccrualForEnvironmentalLossContingenciesIncreaseDecreaseForRevisionInEstimates | 50.0 |
| 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 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 |
| Value | 6.0 | 5.0 | 5.0 | 5.0 | 6.0 | 3.0 | 5.0 | 2.0 | 7.0 | 3.0 | -7.0 | -4.0 | -5.0 | 21 | -8.0 | 15 |
| Percentage of AccrualForEnvironmentalLossContingenciesPayments1 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2021-07-28 |
| Value | 20 |
| Percentage of AssetImpairmentCharges | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 16 | -14.0 | -1.0 | -2.0 | -2.0 | 6.0 |
| Percentage of CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths | 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 |
| Value | -68.0 | -145.0 | -49.0 | -34.0 | -27.0 | 16 |
| Percentage of CashFlowHedgeGainLossToBeReclassifiedWithinTwelveMonths | -425.0 | 1035.7 | 4900.0 | 1700.0 | 1350.0 | 266.7 |
| 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 |
| Value | -5000000.0 | -6000000.0 | -6000000.0 | -5000000.0 | -5000000.0 | -4000000.0 | -3000000.0 | -2000000.0 | -2000000.0 | -3000000.0 | -3000000.0 | -3000000.0 | -4000000.0 | -3000000.0 | -3000000.0 | -3000000.0 | -4000000.0 | -3000000.0 | -5000000.0 | -3000000.0 |
| Percentage of DefinedBenefitPlanAmortizationOfGainsLosses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -50000000.0 | -51000000.0 | -54000000.0 | -54000000.0 | -53000000.0 | -51000000.0 | -44000000.0 | -43000000.0 | -42000000.0 | -42000000.0 | -44000000.0 | -47000000.0 | -52000000.0 | -55000000.0 | -46000000.0 | -47000000.0 | -46000000.0 | -46000000.0 | -47000000.0 | -36000000.0 | -10000000.0 |
| Percentage of DefinedBenefitPlanAmortizationOfGainsLosses | 1000.0 | 850.0 | 900.0 | 1080.0 | 1060.0 | 1275.0 | 1466.7 | 2150.0 | 2100.0 | 1400.0 | 1466.7 | 1566.7 | 1300.0 | 1833.3 | 1533.3 | 1566.7 | 1150.0 | 1533.3 | 940.0 | 1200.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 |
| Value | -4000000.0 | -4000000.0 | -4000000.0 | -4000000.0 | -4000000.0 | -3000000.0 | 0 | -1000000.0 | -2000000.0 | -1000000.0 | -2000000.0 | -1000000.0 | -3000000.0 | -2000000.0 |
| Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit | 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 |
| Period End | 2021-04-01 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 500 | 20 | 100 | 605 |
| Percentage of DefinedBenefitPlanContributionsByEmployer | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-04-01 |
| Value | 500 |
| Percentage of DefinedBenefitPlanContributionsByEmployer | 100.0 |
| Period End | 2021-04-01 |
| Value | 500 |
| Percentage of DefinedBenefitPlanContributionsByEmployer | 100.0 |
| Period End | 2021-04-01 |
| Value | 500 |
| Percentage of DefinedBenefitPlanContributionsByEmployer | 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 |
| Value | 73 | 73 | 72 | 73 | 73 | 74 | 81 | 81 | 82 | 81 | 85 | 84 | 82 | 90 | 100 | 101 | 98 | 99 | 102 | 80 | 31 |
| Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 4.0 | 4.0 | 4.0 | 5.0 | 5.0 | 5.0 | 8.0 | 10.0 | 10.0 | 8.0 | 8.0 | 8.0 | 9.0 | 9.0 | 10.0 | 9.0 | 9.0 | 9.0 | 8.0 | 6.0 | 1.0 |
| Percentage of DefinedBenefitPlanInterestCost | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 29 | 29 | 40 | 41 | 41 | 42 | 54 | 55 | 56 | 56 | 57 | 56 | 55 | 59 | 61 | 62 | 60 | 61 | 57 | 44 | 19 |
| Percentage of DefinedBenefitPlanInterestCost | 725.0 | 725.0 | 1000.0 | 820.0 | 820.0 | 840.0 | 675.0 | 550.0 | 560.0 | 700.0 | 712.5 | 700.0 | 611.1 | 655.6 | 610.0 | 688.9 | 666.7 | 677.8 | 712.5 | 733.3 | 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 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 |
| Value | 6.0 | 17 | 8.0 | 7.0 | 5.0 | 7.0 | 20 | 13 | 13 | 12 | 13 | -43.0 | 13 | -15.0 | 12 | 13 | 12 | 12 | 11 | 8.0 | 1.0 |
| Percentage of DefinedBenefitPlanNetPeriodicBenefitCost | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 50 | 12 | 86 | 41 | 35 | 36 | 97 | 35 | 68 | 30 | 42 | 266 | 208 | 45 | 30 | 31 | 30 | 28 | 26 | 33 | 12 |
| Percentage of DefinedBenefitPlanNetPeriodicBenefitCost | 833.3 | 70.6 | 1075.0 | 585.7 | 700.0 | 514.3 | 485.0 | 269.2 | 523.1 | 250.0 | 323.1 | -618.6 | 1600.0 | -300.0 | 250.0 | 238.5 | 250.0 | 233.3 | 236.4 | 412.5 | 1200.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | -5.0 | 0.0 | 1.0 | -3.0 | -76.0 | 0.0 | 38 | -12.0 | -175.0 | -167.0 | 23 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-03-31 |
| Value | 17 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0.0 | 17 | 0.0 | 0.0 | 0.0 | -1.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments | 0.0 | 0.0 | -0.0 | 0.0 | 0.0 | 33.3 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0.0 | 0.0 | 0.0 | -2.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments | -0.0 | 0.0 | 0.0 | 66.7 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | 0.0 | 17 | 0.0 | 0.0 | 2.0 | 0.0 | 0.0 | 0.0 | 28 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments | 0.0 | 0.0 | -0.0 | 0.0 | 200.0 | -0.0 | -0.0 | -0.0 | 121.7 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 |
| Value | -5.0 | 0.0 | -1.0 | -3.0 | 0.0 | 0.0 | -38.0 | 0.0 | 0.0 | 0.0 | -5.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments | 100.0 | 0.0 | -100.0 | 100.0 | -0.0 | 0.0 | -100.0 | -0.0 | -0.0 | -0.0 | -21.7 |
| Period End | 2020-12-31 | 2020-09-30 | 2019-12-31 | 2019-09-30 | 2018-12-31 |
| Value | 49 | -5.0 | 69 | 5.0 | 0.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 |
| Period End | 2021-03-31 |
| Value | -26.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 | 0.0 |
| Period End | 2021-06-30 |
| Value | -39.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 0.0 | -26.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2018-12-31 | 2018-09-30 |
| Value | 0.0 | -26.0 | 0.0 | 56 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2020-12-31 | 2020-09-30 | 2019-12-31 | 2019-09-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2016-12-31 | 2016-09-30 |
| Value | -39.0 | -46.0 | -5.0 | -68.0 | -5.0 | -11.0 | -232.0 | -167.0 | -2.0 | -3.0 | -3.0 | -13.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 | 0.0 | -93.9 | 100.0 | -98.6 | -100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 0.0 | 9.0 |
| Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlementsAndCurtailments1 | 0.0 | 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 |
| Value | 1.0 | 2.0 | 2.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 2.0 | 1.0 | 1.0 | 1.0 | 2.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Percentage of DefinedBenefitPlanServiceCost | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 5.0 | 5.0 | 13 | 14 | 13 | 14 | 12 | 12 | 12 | 12 | 13 | 13 | 14 | 14 | 18 | 18 | 17 | 18 | 19 | 18 | 12 |
| Percentage of DefinedBenefitPlanServiceCost | 500.0 | 250.0 | 650.0 | 1400.0 | 1300.0 | 1400.0 | 1200.0 | 1200.0 | 1200.0 | 1200.0 | 1300.0 | 650.0 | 1400.0 | 1400.0 | 1800.0 | 900.0 | 1700.0 | 1800.0 | 1900.0 | 1800.0 | 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 | 9.0 | -11.0 | 13 | -1.0 | -2.0 | -24.0 | 4.0 | -10.0 | 5.0 | -6.0 | -3.0 | 6.0 | -11.0 | 4.0 | 6.0 | -3.0 | 4.0 | 7.0 |
| Percentage of EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2016-12-31 | 2016-09-30 | 2016-06-30 |
| Value | 0 | 21.0 | 0.21 | 0 | 0 | 0 | 0.21 | 0.21 | 0 | 0 | 0.35 | 0.35 |
| Percentage of EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate | 0.0 | 100.0 | 100.0 | 0.0 | 0.0 | 0.0 | 100.0 | 100.0 | 0.0 | 0.0 | 100.0 | 100.0 |
| 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 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 |
| Value | 8.0 | 4.0 | 7.0 | -4.0 | -8.0 | -19.0 | -17.0 | -42.0 | -107.0 | -11.0 | -12.0 | -13.0 | -13.0 | -3.0 | -2.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 3.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 | 0.0 |
| Period End | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | -5.0 | 6.0 | -1.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 | -125.0 | 85.7 | 25.0 |
| Period End | 2021-06-30 | 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 | 2.0 | -10.0 | -5.0 | -7.0 | -61.0 | -37.0 | 7.0 | 14 | 68 | -56.0 | 30 | -24.0 | -12.0 | -7.0 | -62.0 | -169.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2020-09-30 | 2020-06-30 |
| Value | 1.0 | 3.0 | -2.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings | 100.0 | 100.0 | 100.0 |
| Period End | 2021-03-31 | 2017-03-31 | 2016-12-31 | 2016-09-30 |
| Value | -6.0 | -5.0 | 12 | -8.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings | 0.0 | 0.0 | 0.0 | 0.0 |
| Period End | 2021-06-30 |
| Value | -1.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings | -100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | -67.0 | -40.0 | -32.0 | -27.0 | -1.0 | -17.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings | -6700.0 | 0.0 | 0.0 | -900.0 | 50.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | -21.0 | 27 | -2.0 | 0.0 | 2.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 417 | 273 | 356 | 335 | 67 | -468.0 |
| Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInOtherComprehensiveIncome | -1985.7 | 1011.1 | 0.0 | -16750.0 | 0.0 | -23400.0 |
| 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 |
| Value | -10.0 | 4.0 | -12.0 | 5.0 | -2.0 | -11.0 | 0.0 | 1.0 | -5.0 | -12.0 | 8.0 | 22 | 30 | -3.0 | -2.0 | -1.0 | 11 | -16.0 | 13 | -8.0 | -1.0 | -12.0 | -23.0 | 35 |
| Percentage of ForeignCurrencyTransactionGainLossBeforeTax | 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 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-06-30 | 2020-03-31 |
| Value | 98 | 26 | -1.0 | 177 |
| Percentage of GainLossOnDispositionOfAssets | 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 | 2018-09-30 | 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 |
| Value | 97 | 27 | -1.0 | -2.0 | -1.0 | 177 | -3.0 | 5.0 | -7.0 | 8.0 | -3.0 | -2.0 | 5.0 | 1.0 | -1.0 | -4.0 | 120 | 0.0 | 132 | 34 | -2.0 | -1.0 | 2.0 |
| Percentage of GainLossOnDispositionOfAssets1 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 3.0 | 27 |
| Percentage of GainLossOnDispositionOfAssets1 | 3.1 | 100.0 |
| Period End | 2021-06-30 |
| Value | 93 |
| Percentage of GainLossOnDispositionOfAssets1 | 95.9 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0.0 | 0.0 | 1.0 | 180 |
| Percentage of GainLossOnDispositionOfAssets1 | -0.0 | -0.0 | -100.0 | 101.7 |
| Period End | 2021-03-31 |
| Value | 27 |
| Percentage of GainLossOnDispositionOfAssets1 | 100.0 |
| Period End | 2021-06-30 |
| Value | 90 |
| Percentage of GainLossOnDispositionOfAssets1 | 92.8 |
| 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 |
| Value | 11 | 10.0 | 4.0 | 12 | 8.0 | 9.0 | 13 | 8.0 | 11 | 11 |
| Percentage of IncomeLossFromEquityMethodInvestments | 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 |
| Value | 8.0 | 1.0 | 9.0 | 5.0 | 5.0 | 3.0 | 0.0 | 7.0 | 1.0 | 13 |
| Percentage of IncomeLossFromEquityMethodInvestments | 72.7 | 10.0 | 225.0 | 41.7 | 62.5 | 33.3 | 0.0 | 87.5 | 9.1 | 118.2 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 |
| Value | 6.0 | 2.0 | 1.0 | -1.0 | 2.0 | 1.0 | 1.0 | 0.0 | -1.0 |
| Percentage of IncomeLossFromEquityMethodInvestments | 54.5 | 20.0 | 25.0 | -8.3 | 25.0 | 11.1 | 12.5 | 0.0 | -9.1 |
| 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 |
| Value | 26 | 7.0 | 3.0 | -11.0 | -20.0 | -6.0 | -14.0 | -6.0 | -16.0 | -11.0 |
| Percentage of IncomeLossFromEquityMethodInvestments | 236.4 | 70.0 | 75.0 | -91.7 | -250.0 | -66.7 | -107.7 | -75.0 | -145.5 | -100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 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 | 35 | 11 | -1.0 | -4.0 | -9.0 | 2.0 | -17.0 | 3.0 | -28.0 | 0.0 | 5.0 | 6.0 | -8.0 | 13 | -15.0 | 1.0 | -14.0 | -14.0 | -16.0 | -4.0 | -21.0 |
| Percentage of IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions | 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 | 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 |
| Value | 96 | -64.0 | 112 | 96 | -62.0 | -121.0 | 46 | -55.0 | 15 | -159.0 | -30.0 | -30.0 | 1.0 | -106.0 | 268 | 90 | 64 | -45.0 | 181 | -42.0 | 19 | -152.0 | -48.0 |
| Percentage of IncreaseDecreaseInAccountsPayableTrade | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -23000000.0 | 3000000.0 | 13000000.0 | -46000000.0 | -35000000.0 | -85000000.0 | -28000000.0 | -96000000.0 | -33000000.0 | -18000000.0 | -31000000.0 | -45000000.0 | -57000000.0 | -186000000.0 | -243000000.0 | -82000000.0 | -57000000.0 | -181000000.0 | 18000000.0 | -124000000.0 | -9000000.0 | -205000000.0 | -23000000.0 |
| Percentage of IncreaseDecreaseInAccruedLiabilities | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 41 | -1.0 | 24 | 88 | 18 | -11.0 | 14 | -2.0 | -299.0 | -43.0 | -7.0 | 147 | 17 | 84 | 96 | 59 | -27.0 | -17.0 | -45.0 | 22 | -65.0 | -60.0 | -207.0 |
| Percentage of IncreaseDecreaseInAccruedTaxesPayable | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 12 | 22 | 18 | 83 | 13 | -32.0 | 0.0 | -8.0 | 22 | 10.0 | 12 | 40 | 36 | 13 | 11 | 42 | 43 | 3.0 | -4.0 | 9.0 |
| Percentage of IncreaseDecreaseInOtherNoncurrentAssets | 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 | 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 |
| Value | -27.0 | -31.0 | -12.0 | -15.0 | -18.0 | -43.0 | -3.0 | -6.0 | -22.0 | 1.0 | -39.0 | -28.0 | -7.0 | -23.0 | -50.0 | 12 | 19 | -20.0 | 55 |
| Percentage of IncreaseDecreaseInOtherNoncurrentLiabilities | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2018-12-31 |
| Value | 3.0 | 0.0 | 156 | 46 | 0.0 |
| Percentage of IncreaseDecreaseInPensionPlanObligations | 100.0 | 0.0 | 100.0 | 100.0 | 0.0 |
| Period End | 2021-06-30 |
| Value | 90 |
| Percentage of IncreaseDecreaseInPensionPlanObligations | 0.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0.0 | 0.0 | 0.0 | 18 |
| Percentage of IncreaseDecreaseInPensionPlanObligations | 0.0 | 0.0 | 0.0 | 39.1 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0.0 | 0.0 | 0.0 | 28 |
| Percentage of IncreaseDecreaseInPensionPlanObligations | 0.0 | 0.0 | 0.0 | 60.9 |
| Period End | 2020-12-31 | 2018-12-31 |
| Value | 0.0 | -23.0 |
| Percentage of IncreaseDecreaseInPostretirementObligations | 0.0 | 100.0 |
| Period End | 2021-03-31 |
| Value | 40 |
| Percentage of IncreaseDecreaseInPostretirementObligations | 0.0 |
| Period End | 2020-12-31 |
| Value | 0.0 |
| Percentage of IncreaseDecreaseInPostretirementObligations | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | -6.0 | 112 |
| Percentage of IncreaseDecreaseInPostretirementObligations | 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 | 2015-12-31 |
| Value | -1.0 | -57.0 | 4.0 | -8.0 | -2.0 | -11.0 | 43 | -2.0 | -55.0 | -13.0 | 35 | -11.0 | 10.0 | -2.0 | 19 | -10.0 | -39.0 | -13.0 | 30 | 11 | -25.0 |
| Percentage of IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 58 | 212 | 10.0 | 98 | -194.0 | 70 | -156.0 | -33.0 | -52.0 | -42.0 | -166.0 | 0.0 | 252 | -43.0 | 6.0 | 37 | 82 | -7.0 | 108 | 102 | 1.0 | 23 | -96.0 |
| Percentage of IncreaseDecreaseInReceivables | 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 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-03-31 | 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 | 3000000.0 | 3000000.0 | 1000000.0 | 0 | 0 | 2000000.0 | 1000000.0 | 0 | 1000000.0 | 1000000.0 | 1000000.0 |
| Percentage of IncrementalCommonSharesAttributableToNonvestedSharesWithForfeitableDividends | 100.0 | 100.0 | 100.0 | 0.0 | 0.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-04-01 | 2021-03-31 |
| Value | 1500 | 1255 |
| Percentage of LineOfCreditFacilityCommitmentFeeAmount | 100.0 | 100.0 |
| Period End | 2021-03-31 |
| Value | -245000000.0 |
| Percentage of LineOfCreditFacilityIncreaseDecreaseForPeriodNet | 100.0 |
| Period End | 2021-06-30 |
| Value | -245000000.0 |
| Percentage of LineOfCreditFacilityIncreaseDecreaseForPeriodNet | 0.0 |
| Period End | 2021-04-07 |
| Value | 750 |
| Percentage of MaturitiesOfSeniorDebt | 100.0 |
| Period End | 2021-04-07 |
| Value | 750 |
| Percentage of MaturitiesOfSeniorDebt | 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 |
| Value | 17 | 21 | 17 | 19 | 20 | 18 | 18 | 21 | 20 | 19 |
| Percentage of OperatingLeaseCost | 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 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 |
| Value | 3000000.0 | 1000000.0 | -10000000.0 | -3000000.0 | 2000000.0 | -3000000.0 | -6000000.0 | -2000000.0 | -6000000.0 | 4000000.0 | 2000000.0 |
| Percentage of OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest | 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 |
| Value | 253 | 131 | -133.0 | -32.0 | -127.0 | 38 | -69.0 | 19 | 10.0 | 41 | -179.0 | 398 | 183 |
| Percentage of OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent | 100.0 | 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 |
| Value | 51 | -60.0 | 124 | 17 | 94 | -245.0 | 45 | -75.0 | 4.0 | 2.0 | -10.0 | -54.0 | -151.0 |
| Percentage of OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToNoncontrollingInterest | 100.0 | 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 |
| Value | 204 | -176.0 | 298 | 5.0 | 135 | -663.0 | 117 | -224.0 | 40 | -22.0 | -18.0 | -142.0 | -445.0 |
| Percentage of OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent | 100.0 | 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 |
| Value | 5.0 | -3.0 | 0.0 | 0.0 | -1.0 | -20.0 | -13.0 | -3.0 | -1.0 | 6.0 | 5.0 | 5.0 | -10.0 |
| Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxNoncontrollingInterest | 100.0 | 100.0 | 0.0 | 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 |
| Value | -266.0 | -204.0 | -247.0 | -240.0 | -390.0 | 701 | -173.0 | 61 | 79 | -288.0 | 372 | -29.0 | -175.0 |
| Percentage of OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTaxParent | 100.0 | 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 |
| Value | 5.0 | -3.0 | 0.0 | 0.0 | -1.0 | -20.0 | -13.0 | -3.0 | -1.0 | 6.0 | 5.0 | 5.0 | -10.0 | -20.0 | -7.0 | -5.0 | -21.0 | 83 | 0.0 | -10.0 | 16 | -2.0 | 2.0 | 1.0 |
| Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax | 100.0 | 100.0 | 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 | 100.0 | 100.0 | 100.0 | 0.0 | 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 |
| Value | -266.0 | -204.0 | -247.0 | -240.0 | -390.0 | 701 | -173.0 | 61 | 79 | -288.0 | 372 | -29.0 | -175.0 | 550 | -410.0 | -415.0 | -6.0 |
| Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax | -5320.0 | 6800.0 | 0.0 | 0.0 | 39000.0 | -3505.0 | 1330.8 | -2033.3 | -7900.0 | -4800.0 | 7440.0 | -580.0 | 1750.0 | -2750.0 | 5857.1 | 8300.0 | 28.6 |
| 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 |
| Value | 59 | -62.0 | 114 | 14 | 95 | -265.0 | 29 | -84.0 | 1.0 | 9.0 | -11.0 | -45.0 | -159.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest | 100.0 | 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 |
| Value | 191 | -249.0 | -82.0 | -267.0 | -382.0 | 76 | -125.0 | -144.0 | 129 | -269.0 | 175 | 227 | -437.0 |
| Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent | 100.0 | 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 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 |
| Value | -2.0 | 12 | 7.0 | -1.0 | 1.0 | 0.0 | 11 | 3.0 | 10.0 | -4.0 | -2.0 | -1.0 | 15 | -6.0 | -19.0 | 1.0 | 1.0 | -1.0 | 8.0 | -10.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax | 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 | 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 |
| Value | -164.0 | -69.0 | 251 | 93 | 181 | 20 | 189 | 38 | 78 | 4.0 | 231 | -174.0 | -1.0 | -75.0 | 713 | 6.0 | -53.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsAndTax | 8200.0 | 0.0 | 2091.7 | 1328.6 | -18100.0 | 2000.0 | 0.0 | 345.5 | 2600.0 | 0.0 | 2310.0 | 4350.0 | 50.0 | 7500.0 | 4753.3 | -100.0 | 278.9 |
| Period End | 2021-06-30 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-09-30 | 2016-06-30 | 2015-12-31 | 2015-09-30 |
| Value | -2.0 | 11 | 5.0 | -1.0 | 1.0 | 4.0 | 7.0 | 3.0 | 8.0 | -3.0 | -2.0 | 15 | -4.0 | -19.0 | 1.0 | 1.0 | -1.0 | 8.0 | -9.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -164.0 | -71.0 | 236 | 87 | 177 | 14 | 189 | 27 | 62 | 3.0 | 236 | -173.0 | -7.0 | -67.0 | 693 | 4.0 | -55.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax | 8200.0 | 0.0 | 2145.5 | 1740.0 | -17700.0 | 1400.0 | 4725.0 | 385.7 | 2066.7 | 0.0 | 2950.0 | 5766.7 | 350.0 | 0.0 | 4620.0 | -100.0 | 289.5 |
| 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 |
| Value | 256 | 132 | 387 | -35.0 | 125 | -38.0 | -54.0 | 13 | 8.0 | -42.0 | 185 | -402.0 | -185.0 | -102.0 | 661 | -49.0 | -122.0 | -43.0 | 223 | -19.0 | -11.0 | 9.0 | 17 | -51.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 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 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 | 2015-09-30 |
| Value | -3.0 | -1.0 | 10.0 | 3.0 | -2.0 | 3.0 | 6.0 | 2.0 | -1.0 | 6.0 | -4.0 | -2.0 | -1.0 | 15 | -5.0 | -20.0 | 1.0 | 1.0 | -2.0 | -1.0 | 6.0 | -9.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax | -1.2 | -0.8 | 2.6 | -8.6 | -1.6 | -5.6 | 46.2 | 25.0 | 2.4 | 3.2 | 1.0 | 1.1 | 1.0 | 2.3 | 10.2 | 16.4 | -2.3 | -5.3 | 18.2 | -11.1 | 35.3 | 17.6 |
| 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 | 2017-09-30 | 2017-06-30 |
| Value | -253.0 | -131.0 | 133 | 32 | 127 | -38.0 | 69 | -19.0 | -10.0 | -41.0 | 179 | -398.0 | -183.0 | -101.0 | 646 | -44.0 | -102.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax | -98.8 | -99.2 | 34.4 | -91.4 | 101.6 | 100.0 | -127.8 | -146.2 | -125.0 | 97.6 | 96.8 | 99.0 | 98.9 | 99.0 | 97.7 | 89.8 | 83.6 |
| Period End | 2020-12-31 | 2020-09-30 | 2019-09-30 | 2018-09-30 | 2018-06-30 | 2018-03-31 | 2017-12-31 | 2017-09-30 | 2015-12-31 | 2015-09-30 |
| Value | 1.0 | 2.0 | 4.0 | -1.0 | 0.0 | -1.0 | 0.0 | -2.0 | 0.0 | -1.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 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 |
| Value | 0.0 | 2.0 | 15 | 6.0 | 4.0 | 6.0 | 0.0 | 11 | 16 | 1.0 | -5.0 | -1.0 | 6.0 | -8.0 | 20 | 2.0 | 2.0 |
| Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBeforeReclassificationAdjustmentsTax | 0.0 | 0.0 | 1500.0 | 300.0 | 0.0 | 0.0 | 0.0 | 275.0 | 0.0 | 0.0 | 0.0 | 100.0 | 0.0 | 800.0 | 0.0 | -100.0 | 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 |
| Value | -67.0 | -52.0 | -39.0 | -29.0 | -13.0 | -25.0 | -8.0 | -13.0 | -10.0 | 9.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 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 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 |
| Value | -3.0 | -2.0 | -2.0 | -1.0 | -14.0 | -2.0 | -12.0 | -8.0 | -4.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 4.5 | 5.1 | 6.9 | 7.7 | 56.0 | 25.0 | 92.3 | 80.0 | -44.4 |
| 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 |
| Value | -60.0 | -55.0 | -40.0 | -26.0 | -14.0 | -8.0 | -2.0 | 8.0 | 5.0 | 31 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 89.6 | 105.8 | 102.6 | 89.7 | 107.7 | 32.0 | 25.0 | -61.5 | -50.0 | 344.4 |
| Period End | 2021-06-30 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 |
| Value | -1.0 | 0.0 | -2.0 | -1.0 | -7.0 | 3.0 | -7.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 1.5 | -0.0 | 6.9 | 7.7 | 28.0 | -37.5 | 53.8 |
| Period End | 2021-06-30 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 |
| Value | -2.0 | -2.0 | 0.0 | 0.0 | -7.0 | -5.0 | -5.0 | -8.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 3.0 | 5.1 | -0.0 | -0.0 | 28.0 | 62.5 | 38.5 | 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 |
| Value | -72.0 | -41.0 | -31.0 | -21.0 | -1.0 | -13.0 | -10.0 | -9.0 | -12.0 | -13.0 | -21.0 | -26.0 | -34.0 | -27.0 | -48.0 | -33.0 | -31.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 107.5 | 78.8 | 79.5 | 72.4 | 7.7 | 52.0 | 125.0 | 69.2 | 120.0 | -144.4 | 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 | 2.0 | -6.0 | -4.0 | -1.0 | -3.0 | 2.0 | 4.0 | 6.0 | 7.0 | 18 | 7.0 | 4.0 | 4.0 | 9.0 | 5.0 | 5.0 | 1.0 | 1.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | -3.0 | 11.5 | 10.3 | 3.4 | 23.1 | -8.0 | -50.0 | -46.2 | -70.0 | 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 |
| Value | 4.0 | -9.0 | -5.0 | -3.0 | -4.0 | -3.0 | 7.0 | 4.0 | 6.0 | 26 | 11 | 6.0 | 7.0 | 13 | 8.0 | 8.0 | 2.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | -6.0 | 17.3 | 12.8 | 10.3 | 30.8 | 12.0 | -87.5 | -30.8 | -60.0 | 288.9 | 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 | 2.0 | 1.0 | -2.0 | -3.0 | -7.0 | -8.0 | -6.0 | -4.0 | -4.0 | -4.0 | -4.0 | -3.0 | 0.0 | 1.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | -3.0 | -1.9 | 5.1 | 10.3 | 53.8 | 32.0 | 75.0 | 30.8 | 40.0 | -44.4 | 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 |
| Value | -1.0 | -3.0 | -1.0 | -2.0 | -1.0 | -1.0 | 0.0 | -4.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 1.5 | 5.8 | 2.6 | 6.9 | 7.7 | 4.0 | -0.0 | 30.8 |
| 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 |
| Value | -4.0 | 3.0 | 3.0 | -1.0 | 2.0 | -3.0 | -4.0 | -9.0 | -7.0 | -18.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 6.0 | -5.8 | -7.7 | 3.4 | -15.4 | 12.0 | 50.0 | 69.2 | 70.0 | -200.0 |
| 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 |
| Value | 2.0 | -6.0 | -4.0 | -1.0 | -3.0 | 2.0 | 4.0 | 6.0 | 7.0 | 18 | 7.0 | 4.0 | 4.0 | 9.0 | 5.0 | 5.0 | 1.0 | 1.0 | 3.0 | 34 | -5.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | -3.0 | 11.5 | 10.3 | 3.4 | 23.1 | -8.0 | -50.0 | -46.2 | -70.0 | 200.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| 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 | -67.0 | -52.0 | -39.0 | -29.0 | -13.0 | -25.0 | -9.0 | -13.0 | -10.0 | 9.0 | -14.0 | -23.0 | -27.0 | -13.0 | -38.0 | -25.0 | -29.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 112.5 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 1.0 | -4.0 | -4.0 | 0.0 | -2.0 | 1.0 | 3.0 | 4.0 | 5.0 | 13 | 5.0 | 3.0 | 3.0 | 6.0 | 3.0 | 4.0 | 0.0 | 1.0 | 1.0 | 24 | -3.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax | 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 | 100.0 | 100.0 | 100.0 | 0.0 | 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 |
| Value | -56.0 | -43.0 | -33.0 | -27.0 | -11.0 | -24.0 | -8.0 | -16.0 | -11.0 | 2.0 | -14.0 | -21.0 | -25.0 | -14.0 | -39.0 | -21.0 | -25.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax | -5600.0 | 1075.0 | 825.0 | 0.0 | 550.0 | -2400.0 | -266.7 | -400.0 | -220.0 | 15.4 | -280.0 | -700.0 | -833.3 | -233.3 | -1300.0 | -525.0 | 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 | 2016-12-31 | 2016-09-30 | 2016-06-30 |
| Value | 1.0 | -2.0 | -2.0 | 1.0 | 1.0 | -1.0 | 1.0 | 2.0 | 2.0 | 5.0 | 2.0 | 1.0 | 1.0 | 3.0 | 2.0 | 1.0 | 1.0 | 2.0 | 10.0 | -2.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -11.0 | -9.0 | -16.0 | 2.0 | 2.0 | 1.0 | -1.0 | 3.0 | 1.0 | 7.0 | 0.0 | -2.0 | -2.0 | 1.0 | 1.0 | -4.0 | -4.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax | -1100.0 | 450.0 | 800.0 | 200.0 | 200.0 | -100.0 | -100.0 | 150.0 | 50.0 | 140.0 | 0.0 | -200.0 | -200.0 | 33.3 | 50.0 | -400.0 | -400.0 |
| 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 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 1.0 | 1.0 | 1.0 | 3.0 | 1.0 | 1.0 | 1.0 | 2.0 | 1.0 | 1.0 | 2.0 | 1.0 | 0.0 | 1.0 | 0.0 | 1.0 | 1.0 | 2.0 | 1.0 | 0.0 | 2.0 | 2.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax | 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 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 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 |
| Value | 89 | 61 | 106 | 57 | 52 | 54 | 122 | 49 | 83 | 45 | 59 | 227 | 224 | 36 | 50 | 50 | 49 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansBeforeTax | 8900.0 | 6100.0 | 10600.0 | 1900.0 | 5200.0 | 5400.0 | 12200.0 | 2450.0 | 8300.0 | 4500.0 | 2950.0 | 22700.0 | 0.0 | 3600.0 | 0.0 | 5000.0 | 4900.0 |
| 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 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 1.0 | 1.0 | 1.0 | 2.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 2.0 | 1.0 | 0.0 | 1.0 | 0.0 | 1.0 | 1.0 | 2.0 | 0.0 | 1.0 | 1.0 | 2.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax | 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 | 0.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 89 | 60 | 103 | 55 | 50 | 52 | 120 | 46 | 72 | 44 | 57 | 225 | 176 | 34 | 47 | 48 | 47 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansNetOfTax | 8900.0 | 6000.0 | 10300.0 | 2750.0 | 5000.0 | 5200.0 | 12000.0 | 4600.0 | 7200.0 | 4400.0 | 2850.0 | 22500.0 | 0.0 | 3400.0 | 0.0 | 4800.0 | 4700.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2019-12-31 | 2019-09-30 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 | 2015-12-31 |
| Value | 0.0 | 1.0 | 0.0 | 1.0 | 0.0 | 1.0 | -1.0 | 1.0 | 0.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 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 | 0.0 | 1.0 | 3.0 | 2.0 | 2.0 | 2.0 | 2.0 | 3.0 | 11 | 1.0 | 2.0 | 2.0 | 48 | 2.0 | 3.0 | 2.0 | 2.0 |
| Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansTax | 0.0 | 0.0 | 0.0 | 200.0 | 0.0 | 0.0 | 0.0 | 300.0 | 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 |
| Value | -397.0 | -303.0 | -351.0 | -333.0 | -513.0 | 852 | -225.0 | 60 | 80 | -352.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | 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 |
| Value | 6.0 | -14.0 | 12 | 3.0 | 22 | -29.0 | 10.0 | -21.0 | 5.0 | -8.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | -1.5 | 4.6 | -3.4 | -0.9 | -4.3 | -3.4 | -4.4 | -35.0 | 6.2 | 2.3 |
| 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 |
| Value | -394.0 | -300.0 | -367.0 | -338.0 | -536.0 | 867 | -252.0 | 104 | 80 | -317.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | 99.2 | 99.0 | 104.6 | 101.5 | 104.5 | 101.8 | 112.0 | 173.3 | 100.0 | 90.1 |
| 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 |
| Value | -9.0 | 11 | 4.0 | 2.0 | 1.0 | 14 | 17 | -23.0 | -5.0 | -27.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | 2.3 | -3.6 | -1.1 | -0.6 | -0.2 | 1.6 | -7.6 | -38.3 | -6.2 | 7.7 |
| 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 |
| Value | 9.0 | -10.0 | -5.0 | -1.0 | -4.0 | -26.0 | -15.0 | 2.0 | 6.0 | 27 | 14 | 12 | -10.0 | -20.0 | -5.0 | -2.0 | -30.0 | 120 | 3.0 | 20 | 18 | -3.0 | 3.0 | 1.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | -2.3 | 3.3 | 1.4 | 0.3 | 0.8 | -3.1 | 6.7 | 3.3 | 7.5 | -7.7 | 0.0 | 0.0 | 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 |
| Value | -397.0 | -303.0 | -351.0 | -333.0 | -513.0 | 852 | -225.0 | 60 | 80 | -352.0 | 459 | -60.0 | -231.0 | 635 | -514.0 | -545.0 | -50.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 6.0 | -7.0 | -4.0 | 0.0 | -3.0 | -19.0 | -10.0 | 1.0 | 4.0 | 19 | 10.0 | 8.0 | -7.0 | -14.0 | -4.0 | -1.0 | -21.0 | 84 | 1.0 | 14 | 13 | -2.0 | 2.0 | 1.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax | 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 | 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 |
| Value | -322.0 | -247.0 | -280.0 | -267.0 | -401.0 | 677 | -181.0 | 45 | 68 | -286.0 | 358 | -50.0 | -200.0 | 536 | -449.0 | -436.0 | -31.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax | -5366.7 | 3528.6 | 7000.0 | 0.0 | 13366.7 | -3563.2 | 1810.0 | 4500.0 | 1700.0 | -1505.3 | 3580.0 | -625.0 | 2857.1 | -3828.6 | 11225.0 | 43600.0 | 147.6 |
| 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 | 2017-09-30 | 2017-06-30 | 2017-03-31 | 2016-12-31 | 2016-09-30 | 2016-06-30 | 2016-03-31 |
| Value | 3.0 | -3.0 | -1.0 | -1.0 | -1.0 | -7.0 | -5.0 | 1.0 | 2.0 | 8.0 | 4.0 | 4.0 | -3.0 | -6.0 | -1.0 | -1.0 | -9.0 | 36 | 2.0 | 6.0 | 5.0 | -1.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | -75.0 | -56.0 | -71.0 | -66.0 | -112.0 | 175 | -44.0 | 15 | 12 | -66.0 | 101 | -10.0 | -31.0 | 99 | -65.0 | -109.0 | -19.0 |
| Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax | -2500.0 | 1866.7 | 7100.0 | 6600.0 | 11200.0 | -2500.0 | 880.0 | 1500.0 | 600.0 | -825.0 | 2525.0 | -250.0 | 1033.3 | -1650.0 | 6500.0 | 10900.0 | 211.1 |
| Period End | 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 | 161 | 152 | 170 | 183 | 184 | 174 | 172 | 174 | 172 | 193 | 194 | 188 | 195 | 190 | 179 |
| Percentage of OtherDepreciationAndAmortization | 100.0 | 100.0 | 100.0 | 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 |
| Value | -29.0 | 1.0 | -21.0 | -6.0 | -1.0 | -4.0 | -11.0 | 5.0 | -1.0 | -23.0 | -5.0 | 32 | 18 | 14 | -1.0 | -34.0 | 12 | -9.0 | 28 | 3.0 | -9.0 | -6.0 | -16.0 |
| Percentage of OtherNoncashIncomeExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 11 | 13 | 19 | 30 | 34 | 37 | 25 | 51 | 28 | 14 | 3.0 | 6.0 | 83 | 10.0 | 15 | 13 | 28 | 17 | 23 |
| Percentage of PaymentsForRestructuring | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2020-09-30 | 2020-06-30 |
| Value | 1.0 | 8.0 | 2.0 |
| Percentage of PaymentsForRestructuring | 5.3 | 26.7 | 5.9 |
| 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 | 2017-03-31 | 2016-12-31 |
| Value | 10.0 | 11 | 16 | 20 | 23 | 20 | 15 | 45 | 28 | 11 | 3.0 | 4.0 | 81 | 7.0 | 7.0 | 13 |
| Percentage of PaymentsForRestructuring | 90.9 | 84.6 | 84.2 | 66.7 | 67.6 | 54.1 | 60.0 | 88.2 | 100.0 | 78.6 | 100.0 | 66.7 | 97.6 | 70.0 | 41.2 | 56.5 |
| 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 |
| Value | 1.0 | 2.0 | 3.0 | 10.0 | 11 | 17 | 10.0 | 6.0 | 0.0 | 3.0 | 0.0 | 2.0 | 2.0 | 3.0 | 5.0 | 6.0 | 9.0 | 10.0 | 10.0 |
| Percentage of PaymentsForRestructuring | 9.1 | 15.4 | 15.8 | 33.3 | 32.4 | 45.9 | 40.0 | 11.8 | 0.0 | 21.4 | 0.0 | 33.3 | 2.4 | 30.0 | 33.3 | 46.2 | 32.1 | 58.8 | 43.5 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 7.0 | 6.0 | 6.0 | 12 | 12 |
| Percentage of PaymentsForRestructuring | 63.6 | 46.2 | 20.0 | 35.3 | 32.4 |
| Period End | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 2.0 | 9.0 | 13 |
| Percentage of PaymentsForRestructuring | 6.7 | 26.5 | 35.1 |
| Period End | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 0.0 | 1.0 | 1.0 |
| Percentage of PaymentsForRestructuring | 0.0 | 2.9 | 2.7 |
| 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 | 75 | 62 | 55 | 46 | 75 | 31 | 84 | 102 | 72 | 214 | 261 | 181 | 118 | 267 | 98 | 89 | 98 | 57 | 57 | 92 | 34 | 50 |
| Percentage of PaymentsOfDividendsMinorityInterest | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 11 | 13 | 28 | 28 | 27 | 25 | 28 | 30 | 30 | 29 | 30 | 32 | 39 | 38 | 21 | 21 | 22 | 21 |
| Percentage of PensionAndOtherPostretirementBenefitExpense | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 507 | 63 | 260 | 24 | 11 | 48 | 106 | 12 | 48 | 7.0 | 52 | 248 | 652 | 40 | 24 | 35 | 26 | 21 | 21 | 12 | 19 | 14 | 30 |
| Percentage of PensionContributions | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 250 |
| Percentage of PensionContributions | 96.2 |
| Period End | 2021-06-30 |
| Value | 94 |
| Percentage of ProceedsFromDivestitureOfBusinesses | 100.0 |
| Period End | 2020-12-31 | 2020-09-30 | 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 | 0.0 | 8.0 | 10.0 | 20 | 1.0 | 20 | 40 | 0.0 | 56 | 53 | 24 | 0.0 | 32 | 24 |
| Percentage of ProceedsFromMinorityShareholders | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 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 |
| Value | -1000000.0 | -3000000.0 | 0 | -3000000.0 | 0 | -1000000.0 | 0 | 0 | 0 | -6000000.0 | 0 | -2000000.0 | -1000000.0 | -5000000.0 | -2000000.0 | 0 | 0 | -6000000.0 |
| Percentage of ProceedsFromPaymentsForOtherFinancingActivities | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 0.0 | 0.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 0.0 | 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 |
| Value | 114 | 591 | 0.0 | -1.0 | 0.0 | 199 | 0.0 | 12 | 0.0 | 11 |
| Percentage of ProceedsFromSaleOfPropertyPlantAndEquipment | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 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 | 4.0 | 0.0 | 1.0 | 0.0 | 1.0 | 0.0 | 1.0 | 7.0 | 15 | 5.0 | 20 | 0.0 | 18 |
| Percentage of ProceedsFromStockOptionsExercised | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 |
| 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 |
| Value | 0.0 | 0.0 | 0.0 | 2.0 | 0.0 | 1.0 | 0.0 | 20 |
| Percentage of ProvisionForDoubtfulAccounts | 0.0 | 0.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 |
| Period End | 2020-09-30 |
| Value | -4.0 |
| Percentage of RestructuringReserveAccrualAdjustment1 | 100.0 |
| Period End | 2020-09-30 |
| Value | -4.0 |
| Percentage of RestructuringReserveAccrualAdjustment1 | 100.0 |
| Period End | 2021-06-30 |
| Value | -5.0 |
| Percentage of RestructuringReserveAccrualAdjustment1 | 0.0 |
| Period End | 2021-06-30 |
| Value | -5.0 |
| Percentage of RestructuringReserveAccrualAdjustment1 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 0.0 | -12.0 |
| Percentage of RestructuringReserveAccrualAdjustment1 | 0.0 | 0.0 |
| Period End | 2020-09-30 | 2020-06-30 |
| Value | 0 | 1000000.0 |
| Percentage of RestructuringReserveTranslationAdjustment | 0.0 | 100.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2018-01-31 |
| Value | 1.0 | 1.0 | 0.0 | 4.0 | -19.0 |
| Percentage of RestructuringReserveTranslationAndOtherAdjustment | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | -1.0 | 0.0 | 1.0 | 2.0 |
| Percentage of RestructuringReserveTranslationAndOtherAdjustment | -100.0 | 0.0 | 0.0 | 50.0 |
| Period End | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 |
| Value | 2.0 | 1.0 | -1.0 | 2.0 |
| Percentage of RestructuringReserveTranslationAndOtherAdjustment | 200.0 | 100.0 | 0.0 | 50.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 |
| Value | 4.0 | 8.0 | 13 | 16 | 18 |
| Percentage of RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 2019-03-31 |
| Value | 1000000.0 | 1000000.0 | 1000000.0 | 0 | 1000000.0 | 2000000.0 | 0 | 1000000.0 | 3000000.0 |
| Percentage of ShortTermLeaseCost | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 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 | 4.0 | 0.0 | 1.0 | 0.0 | 1.0 | 0.0 | 1.0 | 7.0 | 15 | 6.0 | 20 | 2.0 | 15 |
| Percentage of StockIssuedDuringPeriodValueShareBasedCompensation | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 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 | 4.0 | 0.0 | 1.0 | 0.0 | 1.0 | 0.0 | 1.0 | 7.0 | 15 | 6.0 | 20 | 2.0 | 15 |
| Percentage of StockIssuedDuringPeriodValueShareBasedCompensation | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 0.0 | 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 | 2015-12-31 |
| Value | 0.0 | 1.0 | -1.0 | 1.0 | 0.0 | 2.0 | 0.0 | 1.0 | 1.0 | 4.0 | 2.0 | -11.0 | -2.0 | -15.0 | 3.0 | 2.0 | 4.0 | 2.0 | 6.0 | -4.0 | 1.0 | 0.0 |
| Percentage of StockholdersEquityOther | 0.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 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 | -1.0 | 1.0 | 0.0 | 1.0 | 1.0 | 0.0 | 0.0 | 0.0 | 4.0 | 1.0 | 4.0 | 0.0 | -18.0 | 3.0 | 2.0 | 3.0 |
| Percentage of StockholdersEquityOther | 0.0 | 100.0 | -0.0 | 100.0 | 0.0 | 0.0 | 0.0 | 0.0 | 100.0 | 50.0 | -36.4 | -0.0 | 120.0 | 100.0 | 100.0 | 75.0 |
| Period End | 2021-06-30 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-12-31 | 2019-09-30 | 2019-06-30 | 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 | 2015-12-31 |
| Value | 1.0 | 0.0 | 0.0 | 1.0 | 0.0 | 1.0 | 1.0 | 1.0 | -15.0 | -1.0 | 3.0 | 0.0 | 0.0 | 1.0 | 2.0 | 6.0 | -4.0 | 1.0 | 0.0 |
| Percentage of StockholdersEquityOther | 0.0 | 0.0 | 0.0 | 50.0 | 0.0 | 100.0 | 100.0 | 50.0 | 136.4 | 50.0 | -20.0 | 0.0 | 0.0 | 25.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 3.0 | 4.0 | 13 | 166 |
| Percentage of TaxAdjustmentsSettlementsAndUnusualProvisions | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-09-30 | 2020-06-30 | 2020-03-31 | 2019-09-30 | 2019-03-31 | 2018-12-31 | 2018-09-30 | 2018-06-30 | 2017-12-31 | 2017-09-30 | 2017-06-30 | 2016-12-31 | 2016-09-30 |
| Value | 0.0 | -12.0 | 6.0 | 2.0 | 1.0 | 0.0 | 1.0 | 6.0 | 2.0 | 4.0 | 2.0 | -10.0 | 6.0 |
| Percentage of TranslationAdjustmentFunctionalToReportingCurrencyIncreaseDecreaseGrossOfTax | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 0.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2020-03-31 | 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 |
| Value | 2.0 | 5.0 | 1.0 | -3.0 | 2.0 | -11.0 | 6.0 | 8.0 | -6.0 | 17 | -2.0 | -6.0 | -19.0 | 3.0 | -4.0 | 4.0 | -6.0 | -3.0 | -7.0 | -17.0 |
| Percentage of UnrealizedGainLossOnDerivatives | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 4.0 | 1.0 | 4.0 | 2.0 | 1.0 | 4.0 | 4.0 | 4.0 | 5.0 | 3.0 |
| Percentage of VariableLeaseCost | 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 |
| Value | 241 | 254 | 259 | 260 | 263 | 268 | 274 | 207 | 208 | 212 | 214 |
| Percentage of AccrualEnvironmentalLossActiveRemediationFutureRemediationForSignificantIndividualSites | 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 |
| Value | 166 | 164 | 197 |
| Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedOneToFiveYear | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 142 |
| Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedTwoToFiveYear | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | 31 | 39 | 33 |
| Percentage of AccruedCappingClosurePostClosureAndEnvironmentalCost | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | 116 | 110 | 107 |
| Percentage of AccruedCompensationAndRetirementCostsNoncurrent | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 169 |
| Percentage of AccruedTaxesNoncurrent | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 2019-12-31 |
| Value | 2018000.0 | 2074000.0 | 2130000.0 | 2187000.0 | 2244000.0 | 2347000.0 |
| Percentage of AluminumForecastedSalesDesignatedAsFairValueHedgesInKiloMetricTon | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2020-03-31 | 2019-12-31 | 2018-12-31 |
| Value | 2130000.0 | 2298000.0 | 2347000.0 | 2508000.0 |
| Percentage of AluminumFuturesDesignatedAsFairValueHedgesInKiloMetricTon | 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 | 122 | 52 | 40 | 122 | 159 |
| Percentage of AmountCommittedUnderOutstandingSuretyBonds | 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 | 15 | 14 | 16 | 14 | 22 |
| Percentage of AmountCommittedUnderOutstandingSuretyBonds | 12.3 | 26.9 | 40.0 | 11.5 | 13.8 |
| Period End | 2020-12-31 |
| Value | 3.0 |
| Percentage of AmountCommittedUnderOutstandingSuretyBonds | 2.5 |
| Period End | 2020-09-30 |
| Value | 74 |
| Percentage of AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties | 100.0 |
| Period End | 2020-09-30 |
| Value | 74 |
| Percentage of AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties | 100.0 |
| Period End | 2020-09-30 |
| Value | 74 |
| Percentage of AssessedIncomeTaxAmountExclusiveOfInterestAndPenalties | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 278 | 282 | 231 | 238 | 219 | 165 |
| Percentage of ClosureOfResidueAreas | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 56 | 50 |
| Percentage of DeferredEnergyCredits | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 66 | 72 | 91 | 141 | 187 | 264 |
| Percentage of DeferredTaxAssetsDepreciation | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 37 | 41 |
| Percentage of DeferredTaxAssetsLeasingArrangements | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 434 | 438 | 428 | 432 | 499 | 529 |
| Percentage of DeferredTaxLiabilitiesDepreciation | 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 | 590 | 600 | 571 | 668 | 884 |
| Percentage of DeferredTaxLiabilitiesGross | 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 | -57.0 | -42.0 | -40.0 | -45.0 | -36.0 |
| Percentage of DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveLossAttributedToJointVenturePartners | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 560 |
| Percentage of DefinedBenefitPlanExpectedFutureBenefitPayments | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 |
| Value | 4150 | 4175 | 4175 | 4845 |
| Percentage of DefinedBenefitPlanExpectedFutureBenefitPayments | 741.1 | 0.0 | 0.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | -45.0 | -34.0 | -33.0 | 37 | 30 |
| Percentage of DefinedBenefitPlanFundedAmountsAttributedToJointVenturePartners | 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 | 218 | 107 | 172 | 251 | 259 |
| Percentage of DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect | 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 | 3508 | 3327 | 3242 | 3733 | 3260 |
| Percentage of DefinedBenefitPlanNetAmountRecognizedBeforeTaxEffect | 1609.2 | 3109.3 | 1884.9 | 1487.3 | 1258.7 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 892 | 848 | 973 | -1218.0 | -1286.0 |
| Percentage of DefinedBenefitPlanNetFundedStatus | 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 | 1503 | 1483 | 1354 | -2280.0 | -1818.0 |
| Percentage of DefinedBenefitPlanNetFundedStatus | 168.5 | 174.9 | 139.2 | 187.2 | 141.4 |
| Period End | 2020-12-31 |
| Value | 1170.0 |
| Percentage of DefinedBenefitPlanNumberOfEmployeesOnRollingOperations | 100.0 |
| Period End | 2020-12-31 | 2020-03-31 | 2019-12-31 | 2018-12-31 | 2018-09-30 |
| Value | 11280.0 | 450.0 | 18200.0 | 20600.0 | 20600.0 |
| Percentage of DefinedBenefitPlanNumberOfPlanParticipantsAffected | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 430.0 |
| Percentage of DefinedBenefitPlanNumberOfPlanParticipantsAffected | 3.8 |
| Period End | 2020-12-31 |
| Value | 900.0 |
| Percentage of DefinedBenefitPlanNumberOfPlanParticipantsAffected | 8.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 72 | 85 | 76 | 113 | 121 | 103 |
| Percentage of Demolition | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 1031 |
| Percentage of DisposalGroupIncludingDiscontinuedOperationAccumulatedDepreciation | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 66 | 72 |
| Percentage of DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 |
| Value | 66 | 72 |
| Percentage of DisposalGroupIncludingDiscontinuedOperationOtherPostretirementBenefitLiabilitiesAssumed | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 1423 |
| Percentage of DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentGrossNoncurrent | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | -40.0 | -35.0 | -32.0 | 31 |
| Percentage of EquityMethodInvestmentUnrecognizedGainLoss | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-11-30 |
| Value | 100 |
| Percentage of ExpectedFutureSiteSeparationAndTransactionCostsPayment | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 439 | 437 | 458 | 510 | 471 | 288 |
| Percentage of GasSupplyPrepayment | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 439 | 437 |
| Percentage of GasSupplyPrepayment | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 42 | 21 |
| Percentage of GasSupplyPrepayment | 9.6 | 4.8 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | 481 | 458 | 458 |
| Percentage of GasSupplyPrepayment | 109.6 | 104.8 | 100.0 |
| Period End | 2020-07-07 | 2020-06-30 | 2020-03-31 | 2019-12-31 |
| Value | 152 | 144 | 129 | 144 |
| Percentage of IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-07-07 |
| Value | 147 |
| Percentage of IncomeTaxPayablePossibleUnrecordedAssessedAmountFromTaxingAuthority | 96.7 |
| Period End | 2020-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 1000 | 1000 | 500 |
| Percentage of IncrementalAmountOfConvenantMaximum | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 2.0 | 2.0 | 2.0 | 3.0 | 4.0 |
| Percentage of IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 |
| Value | 6.0 | 22 | 35 | 55 |
| Percentage of IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate | 300.0 | 1100.0 | 1750.0 | 1833.3 |
| Period End | 2020-12-31 | 2019-12-31 |
| Value | 346 | 356 |
| Percentage of IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate | 17300.0 | 17800.0 |
| Period End | 2020-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 400 | 400 | 250 |
| Percentage of InvestmentNegativeCovenantMaximum | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 |
| Value | 23 | 24 | 28 |
| Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour | 100.0 | 100.0 | 100.0 |
| Period End | 2021-03-31 |
| Value | 70 |
| Percentage of LiabilitiesRecordedFromDisposalGroupIncludingDiscontinuedOperation | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2021-03-04 | 2020-12-31 | 2020-09-30 | 2019-12-31 |
| Value | 3034 | 1687 | 750 | 1322 | 1230 | 1200 |
| Percentage of LineOfCreditFacilityMaximumAdditionalBorrowingCapacity | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | 264 | 205 | 198 |
| Percentage of MineReclamationAndClosingLiability | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 |
| Value | 80 |
| Percentage of MinimumRequiredCashContributionToPensionPlanExceptedFuturePaymentsRemainderOfFiscalYear | 100.0 |
| Period End | 2020-07-07 |
| Value | 502 |
| Percentage of NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount | 100.0 |
| Period End | 2020-07-07 |
| Value | 488 |
| Percentage of NoticesIncludeClaimsForCompoundedInterestOnTheTaxAmount | 97.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 5.0 | 8.0 | 11 | 13 | 11 | 19 |
| Percentage of OutstandingReceivableForLaborAndOtherEmployeeRelatedExpenses | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 83 |
| Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesHeldForSale | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 315 | 281 | 275 | 300 | 270 | 268 |
| Percentage of PrepaidGasTransmissionContract | 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 | 2015-12-31 |
| Value | 6855 | 7595 | 7921 | 8751 | 8827 | 8906 |
| Percentage of PropertiesPlantsAndEquipmentExcludingConstructionWorkInProgress | 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 | 8.0 | 8.0 | 19 | 2.0 | 15 |
| Percentage of ReceivablesExcludedFromPensionPlanAssets | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 100 | 100 | 100 | 0.0 |
| Percentage of RestrictedPaymentsNegativeCovenantMaximum | 100.0 | 100.0 | 100.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1032 | 1092 | 1335 | 1383 | 1364 | 1518 |
| Percentage of SegmentReportingInformationEquityMethodInvestments | 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 | 2015-12-31 |
| Value | 264 | 293 | 290 | 262 | 342 | 503 |
| Percentage of SegmentReportingInformationEquityMethodInvestments | 25.6 | 26.8 | 21.7 | 18.9 | 25.1 | 33.1 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 546 | 587 | 856 | 930 | 520 | 497 |
| Percentage of SegmentReportingInformationEquityMethodInvestments | 52.9 | 53.8 | 64.1 | 67.2 | 38.1 | 32.7 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 222 | 212 | 189 | 191 | 163 | 164 |
| Percentage of SegmentReportingInformationEquityMethodInvestments | 21.5 | 19.4 | 14.2 | 13.8 | 12.0 | 10.8 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 |
| Value | -193000000.0 | -170000000.0 | -271000000.0 |
| Percentage of SegmentReportingInformationIntersegmentReceivable | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 12015 | 12325 | 13813 | 14798 | 14394 | 14209 |
| Percentage of SegmentReportingInformationReportedAssets | 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 | 2015-12-31 |
| Value | 4333 | 4303 | 4643 | 5129 | 4791 | 4721 |
| Percentage of SegmentReportingInformationReportedAssets | 36.1 | 34.9 | 33.6 | 34.7 | 33.3 | 33.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 6214 | 6588 | 7722 | 8060 | 5182 | 5612 |
| Percentage of SegmentReportingInformationReportedAssets | 51.7 | 53.5 | 55.9 | 54.5 | 36.0 | 39.5 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 1468 | 1434 | 1448 | 1609 | 1541 | 1443 |
| Percentage of SegmentReportingInformationReportedAssets | 12.2 | 11.6 | 10.5 | 10.9 | 10.7 | 10.2 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 94 | 97 | 97 | 99 | 99 |
| Percentage of SegmentReportingReconcilingItemsGoodwillAssets | 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 | 47 | 48 | 49 | 49 | 50 |
| Percentage of SegmentReportingReconcilingItemsGoodwillAssets | 50.0 | 49.5 | 50.5 | 49.5 | 50.5 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 108 | 106 | 113 | 125 | 135 | 141 |
| Percentage of SpentPotLiningDisposal | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 |
| Value | 80 | 81 | 82 |
| Percentage of TaxAssessmentDeposit | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 82 |
| Percentage of TaxAssessmentDepositNoncurrent | 100.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 200 | 200 | 200 | 0.0 |
| Percentage of ThresholdsForInvestmentsNegativeCovenants | 100.0 | 100.0 | 100.0 | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2017-12-31 | 2016-12-31 |
| Value | 250 | 250 | 250 | 0.0 |
| Percentage of ThresholdsForRestrictedPaymentsNegativeCovenants | 100.0 | 100.0 | 100.0 | 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 | 2015-12-31 |
| Value | 298 | 311 | 322 | 321 | 323 | 327 | 335 | 269 | 271 | 276 | 280 | 285 | 291 | 284 | 294 | 306 | 317 | 324 | 324 | 231 | 235 |
| Percentage of AccrualForEnvironmentalLossContingencies | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 57 | 57 | 63 | 61 | 60 | 59 | 61 | 62 | 63 | 64 | 66 |
| Percentage of AccrualForEnvironmentalLossContingencies | 19.1 | 18.3 | 19.6 | 19.0 | 18.6 | 18.0 | 18.2 | 23.0 | 23.2 | 23.2 | 23.6 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 |
| Value | 113 | 123 | 151 | 115 |
| Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedDueAfterFifthYear | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-09-30 |
| Value | 19 | 24 | 9.0 |
| Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedDueInRemainderOfFiscalYear | 100.0 | 100.0 | 100.0 |
| Period End | 2020-12-31 |
| Value | 29 |
| Percentage of AccrualForEnvironmentalLossContingenciesUndiscountedDueWithinOneYear | 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 | 2015-12-31 |
| Value | 36 | 33 | 29 | 32 | 46 | 38 | 39 | 31 | 34 | 33 | 44 | 37 | 54 | 50 | 36 | 36 | 51 | 60 | 60 | 31 | 28 |
| Percentage of AccruedEnvironmentalLossContingenciesCurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2015-12-31 |
| Value | 262 | 278 | 293 | 289 | 277 | 289 | 296 | 238 | 237 | 243 | 236 | 248 | 237 | 234 | 258 | 270 | 266 | 263 | 264 | 201 | 207 |
| Percentage of AccruedEnvironmentalLossContingenciesNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2015-12-31 |
| Value | 191 | 204 | 209 | 244 | 245 | 299 | 276 | 299 | 320 | 300 | 301 | 297 | 256 | 285 | 309 | 318 | 348 | 352 | 310 | 351 | 508 |
| Percentage of AccruedIncomeTaxesNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2020-09-30 |
| Value | 153 |
| Percentage of AccruedIncomeTaxesNoncurrent | 62.7 |
| Period End | 2020-12-31 |
| Value | 169 |
| Percentage of AccruedIncomeTaxesNoncurrent | 80.9 |
| Period End | 2021-06-30 | 2021-03-31 | 2020-12-31 | 2020-09-30 | 2020-06-30 | 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 | 2014-12-31 | 2013-12-31 |
| Value | 1.0 | -4.0 | -1.0 | -1.0 | -1.0 | 20 | 33 | 36 | 37 | 31 | 26 | 21 | 31 | 51 | 58 | 63 | 84 | 1.0 | 1.0 | 11 | -5.0 | -3.0 | -5.0 | -6.0 | -2.0 | -2.0 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2015-12-31 |
| Value | -1178.0 | -912.0 | -708.0 | -461.0 | -221.0 | 169 | -532.0 | -359.0 | -420.0 | -499.0 | -211.0 | -583.0 | -554.0 | -379.0 | -929.0 | -519.0 | -104.0 | -98.0 | 210 | 603 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossCumulativeChangesInNetGainLossFromCashFlowHedgesEffectNetOfTax | -117800.0 | 22800.0 | 70800.0 | 46100.0 | 22100.0 | 0.0 | -2660.0 | -1087.9 | -1166.7 | -1348.6 | -680.6 | -2242.3 | -2638.1 | -1222.6 | -1821.6 | -894.8 | -165.1 | -116.7 | 21000.0 | -20100.0 |
| 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 | 2014-12-31 | 2013-12-31 |
| Value | 63 | 66 | 67 | 57 | 54 | 56 | 56 | 53 | -47.0 | -45.0 | 46 | 40 | 44 | 46 | 47 | 32 | 37 | 57 | 56 | 54 | 53 | 55 | 56 | 50 | 59 | 64 | 51 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2015-12-31 |
| Value | 2152 | 2405 | 2536 | 2403 | 2371 | 2244 | 2282 | 2213 | -2232.0 | -2242.0 | 2283 | 2104 | 2502 | 2685 | 2786 | 2140 | 2184 | 2286 | 2330 | 352 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax | 3415.9 | 3643.9 | 3785.1 | 4215.8 | 4390.7 | 4007.1 | 4075.0 | 4175.5 | 4748.9 | 4982.2 | 4963.0 | 5260.0 | 5686.4 | 5837.0 | 5927.7 | 6687.5 | 5902.7 | 4010.5 | 4160.7 | 628.6 |
| 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 | 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 | 2014-12-31 | 2013-12-31 |
| Value | -853.0 | -904.0 | -844.0 | -968.0 | -985.0 | -1079.0 | -834.0 | -879.0 | -804.0 | -808.0 | -810.0 | -800.0 | -746.0 | -595.0 | -581.0 | -556.0 | -600.0 | -563.0 | -677.0 | -595.0 | -640.0 | -672.0 | -779.0 | -867.0 | -569.0 | -351.0 | -115.0 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 | 2015-12-31 |
| Value | -2357.0 | -2561.0 | -2385.0 | -2683.0 | -2688.0 | -2823.0 | -2160.0 | -2277.0 | -2053.0 | -2093.0 | -2071.0 | -2053.0 | -1911.0 | -1466.0 | -1467.0 | -1374.0 | -1515.0 | -1416.0 | -1655.0 | -1851.0 |
| Percentage of AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax | 276.3 | 283.3 | 282.6 | 277.2 | 272.9 | 261.6 | 259.0 | 259.0 | 255.3 | 259.0 | 255.7 | 256.6 | 256.2 | 246.4 | 252.5 | 247.1 | 252.5 | 251.5 | 244.5 | 237.6 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 | 2014-12-31 |
| Value | 753 | 717 | 651 | 725 | 708 | 635 | 648 |
| Percentage of AssetRetirementObligation | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 |
| Period End | 2021-07-28 |
| Value | 10.0 |
| Percentage of AssetRetirementObligation | 0.0 |
| Period End | 2021-07-28 |
| Value | 5.0 |
| Percentage of AssetRetirementObligation | 0.0 |
| Period End | 2020-12-31 | 2019-12-31 | 2018-12-31 | 2017-12-31 | 2016-12-31 | 2015-12-31 |
| Value | 128 | 111 | 122 | 108 | 104 | 96 |
| Percentage of AssetRetirementObligationCurrent | 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 |
| Value | 584 | 596 | 625 | 553 | 565 | 548 | 606 | 491 | 529 | 543 | 529 | 528 | 560 | 631 | 617 | 627 | 632 | 635 | 604 |
| Percentage of AssetRetirementObligationsNoncurrent | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 100.0 | 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 |
| Value | 648 |
| Percentage of AssetsOfDisposalGroupIncludingDiscontinuedOperation | 100.0 |
| Period End | 2020-12-31 |
| Value< |