MSEX

Line plots across dimensions of each concept
Tables

Table of contents

us-gaap:CommonStockValue
us-gaap:StatementEquityComponents
us-gaap:SharesOutstanding

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesAuthorized

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

us-gaap:RegulatedAndUnregulatedOperatingRevenue
us-gaap:ConsolidationItems
us-gaap:StatementBusinessSegments

us-gaap:OperatingExpenses

us-gaap:OperatingIncomeLoss
us-gaap:StatementBusinessSegments

us-gaap:InterestExpense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:NonoperatingIncomeExpense

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxesPaidNet

us-gaap:NetIncomeLoss
us-gaap:StatementBusinessSegments
us-gaap:StatementEquityComponents

us-gaap:PreferredStockDividendsIncomeStatementImpact

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersDiluted

us-gaap:Assets
us-gaap:ConsolidationItems
us-gaap:StatementBusinessSegments

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:AccountsReceivableNetCurrent

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OtherAssetsNoncurrent

us-gaap:LiabilitiesCurrent

us-gaap:NotesPayableCurrent

us-gaap:LongTermDebtCurrent

us-gaap:AccountsPayableCurrent

us-gaap:AccruedIncomeTaxesCurrent

us-gaap:OtherLiabilitiesCurrent

us-gaap:LongTermDebt
us-gaap:DebtInstrument

us-gaap:LongTermDebtNoncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:CommonStockValue

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:StatementBusinessSegments
us-gaap:StatementEquityComponents

us-gaap:DepreciationDepletionAndAmortization

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:IncreaseDecreaseInAccountsReceivable

us-gaap:DeferredIncomeTaxExpenseBenefit

us-gaap:ShareBasedCompensation

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment
us-gaap:StatementBusinessSegments

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:ProceedsFromIssuanceOfLongTermDebt
dei:LegalEntity

us-gaap:RepaymentsOfLongTermDebt

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:RepaymentsOfLongTermDebt

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:ProceedsFromRepaymentsOfShortTermDebt

msex:ChangeInUnbilledRevenues

msex:CommercialOperatingRevenues

msex:CostOfTreatedWater

msex:CostOfUntreatedWater

msex:IndustrialOperatingRevenues

msex:InterSegmentEliminationOperatingRevenues

msex:NonregualtedContractOperationsRevenue

msex:OperationsAndMaintenance

msex:OtherNonregulatedRevenues

msex:ResidentialCommercialIndustrialAndFireProtectionRevenue

msex:ResidentialOperatingRevenues

msex:WholesaleMunicipalRevenue

us-gaap:AllowanceForFundsUsedDuringConstructionInvestingActivities

us-gaap:CommonStockDividendsPerShareCashPaid

us-gaap:ContributionOfProperty
us-gaap:StatementClassOfStock
us-gaap:ConvertiblePreferredDividendsNetOfTax

us-gaap:CostOfPurchasedWater
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanServiceCost

us-gaap:Depreciation

us-gaap:DividendsCommonStockCash
us-gaap:StatementEquityComponents

us-gaap:DividendsPreferredStockCash
us-gaap:StatementEquityComponents

us-gaap:IncreaseDecreaseInAccountsPayable

us-gaap:IncreaseDecreaseInAccruedTaxesPayable

us-gaap:IncreaseDecreaseInDeferredRevenue

us-gaap:IncreaseDecreaseInInterestPayableNet

us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations

us-gaap:IncreaseDecreaseInPrepaidExpense

us-gaap:IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories
us-gaap:StatementClassOfStock
us-gaap:IncrementalCommonSharesAttributableToConversionOfPreferredStock

us-gaap:InterestPaidCapitalized

us-gaap:InterestPaidNet

us-gaap:LeaseAndRentalExpense

us-gaap:LifeInsuranceCorporateOrBankOwnedChangeInValue

us-gaap:LineOfCreditFacilityInterestRateDuringPeriod

us-gaap:LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod
us-gaap:PurchaseCommitmentExcludingLongtermCommitment
us-gaap:LongTermPurchaseCommitmentMinimumQuantityRequired

us-gaap:NumberOfReportableSegments

us-gaap:PaymentsOfDebtIssuanceCosts

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock

us-gaap:PaymentsOfStockIssuanceCosts
us-gaap:RetirementPlanType
us-gaap:PensionAndOtherPostretirementBenefitContributions

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity
us-gaap:RegulatoryAgency, dei:LegalEntity
us-gaap:PublicUtilitiesApprovedRateIncreaseDecreaseAmount

us-gaap:RegulatedOperatingRevenueOther

us-gaap:StockIssuedDuringPeriodSharesDividendReinvestmentPlan
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesRestrictedStockAwardGross
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures

us-gaap:StockIssuedDuringPeriodValueDividendReinvestmentPlan
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardGross
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures
us-gaap:StatementEquityComponents

us-gaap:StockholdersEquityOther
us-gaap:StatementEquityComponents

us-gaap:TaxesOther

msex:AccumulatedDeferredIncomeTaxes

msex:ConstructionAdvances
dei:LegalEntity
msex:ConstructionLoanMaximumBorrowingCapacity
us-gaap:LineOfCreditFacility
us-gaap:LongtermDebtType

msex:DeferredChargesAndOtherAssets
us-gaap:FairValueByMeasurementBasis
msex:FirstMortgageBondsFairValueDisclosure

msex:NonUtilityAssetsNet
us-gaap:RegulatoryAgency, dei:LegalEntity
msex:OtherLoanSourceMaximumBorrowingCapacity

msex:PreliminarySurveyAndInvestigationCharges
us-gaap:TaxPeriod
msex:ReserveProvision

msex:RightOfUseAssetsAccumulatedAmortization

msex:RightOfUseAssetsCurrent

msex:TotalCommonEquity
us-gaap:StatementEquityComponents

us-gaap:CapitalizationLongtermDebtAndEquity

us-gaap:ContributionsInAidOfConstruction

us-gaap:DebtInstrumentUnamortizedDiscount

us-gaap:DebtInstrumentUnamortizedPremium

us-gaap:DeferredRevenueCurrent

us-gaap:GuarantyLiabilities

us-gaap:InterestPayableCurrent

us-gaap:LiabilitiesOtherThanLongtermDebtNoncurrent

us-gaap:LineOfCreditFacilityCurrentBorrowingCapacity
us-gaap:LineOfCreditFacility

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity
us-gaap:LineOfCreditFacility
us-gaap:SubsequentEventType

us-gaap:OperatingLeaseLiability

us-gaap:OtherLongTermDebt

us-gaap:OtherLongTermDebtCurrent

us-gaap:PreferredStockSharesAuthorized

us-gaap:PreferredStockSharesOutstanding
us-gaap:StatementClassOfStock

us-gaap:PreferredStockValue
us-gaap:StatementClassOfStock

us-gaap:PrepaidExpenseCurrent

us-gaap:PublicUtilitiesInventory

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentNet

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentPlantInService

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentTransmissionAndDistribution

us-gaap:RegulatoryAssetsNoncurrent

us-gaap:RegulatoryLiabilityNoncurrent

us-gaap:RestrictedCashAndCashEquivalentsNoncurrent

us-gaap:UnbilledReceivablesCurrent

Tables

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:CommonStockValue	███▃▂▂▁▁▁▁▁▁▁▁	216.365	215.6	215.125	170.562	165.138	160.142	157.354	156.741	156.251	155.58	155.12	154.626	154.075	153.506
us-gaap:SharesOutstanding us-gaap:StatementEquityComponents us-gaap:CommonStock	███▃▂▂▁▁▁▁▁	17.464	17.439	17.434	16.67	16.554	16.451	16.403	16.398	16.392	16.358	16.352	NA	NA	NA
us-gaap:CommonStockSharesOutstanding	███▃▃▂▂▂▂▁▁▁▁▁	17.464	17.439	17.434	16.67	16.554	16.451	16.403	16.398	16.392	16.358	16.352	16.345	16.336	16.303
us-gaap:CommonStockSharesAuthorized	▄▄▄▄▄▄▄▄▄▄▄▄▄▄	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0	40.0
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding	█▁	17.577	17.552	NA	16.757	16.675	16.584	NA	16.55	16.544	16.51	NA	16.496	16.488	0.016455
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic	█▁	17.462	17.437	NA	16.61	16.519	16.428	NA	16.394	16.388	16.354	NA	16.34	16.332	0.016299
us-gaap:EarningsPerShareBasic	▅▃▄▇▄▃▃█▅▁▂▄▂▁	0.55	0.44	0.46	0.67	0.49	0.4	0.43	0.75	0.53	0.27	0.32	0.47	0.33	0.27
us-gaap:EarningsPerShareDiluted	▅▄▄▇▄▃▃█▅▁▂▄▂▁	0.55	0.44	0.46	0.66	0.49	0.39	0.43	0.74	0.52	0.27	0.32	0.46	0.33	0.27

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax	▅▂▃▇▄▁▄█▅▂▂▆▃▁	35.241	31.733	32.702	37.735	33.358	30.663	33.231	38.68	34.886	31.143	31.417	36.142	32.982	30.092
us-gaap:RegulatedAndUnregulatedOperatingRevenue	▅▂▃▇▄▁▄█▅▂▂▆▃▁	35.277	31.769	32.738	37.769	33.393	30.698	33.268	38.713	34.919	31.177	31.456	36.174	33.014	30.131
us-gaap:OperatingExpenses	█▆▆▇▅▃█▇▄▆▂▃▃▁	25.892	25.242	25.181	25.786	24.443	23.67	26.115	25.795	24.198	24.827	22.985	23.368	23.451	22.351
us-gaap:OperatingIncomeLoss	▄▁▂▇▄▂▂█▆▁▃█▄▃	9.385	6.527	7.559	11.983	8.95	7.028	7.153	12.918	10.721	6.35	8.471	12.806	9.563	7.78
us-gaap:InterestExpense	▆▅█▆▅▂▆▅▇▂▄▄▄▁	1946000.0	1669000.0	2280000.0	1996000.0	1788000.0	1200000.0	1829000.0	1723000.0	2068000.0	1138000.0	1541000.0	1493000.0	1469000.0	1003000.0
us-gaap:OtherNonoperatingIncomeExpense	▅▆▁▄▃▃▅▆▇▅█▄▄▄	334000.0	385000.0	-512000.0	-4000.0	-80000.0	-57000.0	353000.0	409000.0	571000.0	297000.0	846000.0	43000.0	47000.0	6000.0
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest	▄▂▁▇▃▂▂█▅▁▃▇▄▂	8.568	6.366	5.882	10.854	7.725	6.286	6.234	12.028	9.438	5.676	7.183	11.53	8.299	6.897
us-gaap:NonoperatingIncomeExpense	▆█▃▅▃▃▅▅▄▃▂▁▁▁	1129000.0	1508000.0	604000.0	867000.0	563000.0	458000.0	910000.0	833000.0	785000.0	464000.0	253000.0	217000.0	205000.0	120000.0
us-gaap:IncomeTaxExpenseBenefit	▂▂▁▃▃▃▃▃▄▅▆█▇▆	-1.145	-1.302	-2.188	-0.265	-0.421	-0.266	-0.759	-0.262	0.763	1.182	1.837	3.888	2.918	2.456
us-gaap:IncomeTaxesPaidNet	▂▁▆▂█▂▃▃	0.375	0.002	3.587	0.91	5.027	0.815	1.498	1.202	NA	NA	1.292	0.748	NA	NA
us-gaap:NetIncomeLoss	▆▄▄▇▄▃▃█▅▁▂▄▂▁	9.713	7.668	8.071	11.119	8.146	6.552	6.993	12.29	8.675	4.494	5.345	7.642	5.381	4.441
us-gaap:PreferredStockDividendsIncomeStatementImpact	▁▁▁▁██████████	30000.0	30000.0	30000.0	30000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic	▆▄▄▇▄▃▃█▅▁▂▄▂▁	9.683	7.638	8.04	11.089	8.11	6.516	6.957	12.254	8.639	4.458	5.31	7.606	5.345	4.405
us-gaap:NetIncomeLossAvailableToCommonStockholdersDiluted	▄	9.7	NA	8.057	11.106	8.133	6.539	6.98	12.277	8.662	4.481	5.333	7.629	5.368	4.428

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Operating Margin us-gaap:StatementBusinessSegments us-gaap:RegulatedOperation	▆▃▄█▄▂▃█▅▂▂▆▃▁	32289000.0	28937000.0	29736000.0	35000000.0	30444000.0	27898000.0	28899000.0	34628000.0	31168000.0	27206000.0	27431000.0	32252000.0	29278000.0	26493000.0
Operating Margin us-gaap:StatementBusinessSegments us-gaap:UnregulatedOperation	▂▁▂▁▂▁█▇▅▆▇▆▅▅	3180000.0	2961000.0	3145000.0	3020000.0	3087000.0	2925000.0	4492000.0	4304000.0	3882000.0	4100000.0	4157000.0	4142000.0	3863000.0	3750000.0

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:Assets	██▇▇▅▄▄▄▃▃▂▂▁▁	950.87	935.316	909.878	887.353	807.571	782.973	767.83	752.798	729.744	705.002	661.14	651.919	638.73	627.261
us-gaap:LiabilitiesAndStockholdersEquity	██▇▇▅▄▄▄▃▃▂▂▁▁	950.87	935.316	909.878	887.353	807.571	782.973	767.83	752.798	729.744	705.002	661.14	651.919	638.73	627.261

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:AssetsCurrent	█▇▂▅▄▃▃▅▃▁▃▃▃▂	43.989	40.01	29.133	34.711	32.283	29.65	30.815	35.372	31.059	25.163	29.247	30.088	29.719	27.008
us-gaap:CashAndCashEquivalentsAtCarryingValue	▇█▁▂▂▃▂▂▁▁▃▁▂▃	13.196	15.419	2.23	3.151	2.99	4.986	3.705	3.579	2.673	1.994	4.937	2.701	3.689	5.592
us-gaap:AccountsReceivableNetCurrent	▇▄▆█▅▃▅█▄▃▄▅▃▁	12.619	10.823	11.908	13.407	11.756	9.982	11.762	13.544	11.011	9.97	10.785	11.73	9.953	8.846

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:OperatingLeaseRightOfUseAsset	▁▂▄▅▇█	5573000.0	5757000.0	5944000.0	6133000.0	6323000.0	6517000.0	NA	NA	NA	NA	NA	NA	NA	NA
us-gaap:OtherAssetsNoncurrent	▆▇▇████▁▂▁▁▁▁▂	1408000.0	1837000.0	1899000.0	1954000.0	1983000.0	2010000.0	2093000.0	94000.0	435000.0	148000.0	177000.0	196000.0	226000.0	252000.0

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:LiabilitiesCurrent	▆▅▃██▇▇▇▅▃▃▂▂▁	84.294	80.539	64.981	103.475	102.532	93.246	94.363	94.41	81.575	64.026	64.537	59.012	55.417	49.503
us-gaap:NotesPayableCurrent	▅▄▂██▆▆▆▅▃▃▃▁▁	37.5	33.5	20.0	58.5	59.4	49.5	48.5	48.5	39.0	27.5	28.0	24.5	17.0	14.5
us-gaap:LongTermDebtCurrent	█▇▇▇████▇▆▅▃▁▁	7.34	7.171	7.178	7.161	7.353	7.336	7.343	7.327	7.236	6.982	6.865	6.547	6.164	6.148
us-gaap:AccountsPayableCurrent	▇██▆▅▃▆▆▄▂▃▂▄▁	22.803	24.116	23.306	20.178	18.056	13.976	19.325	19.535	16.413	11.014	13.929	12.113	15.045	8.987
us-gaap:AccruedIncomeTaxesCurrent	▃▄▁▄▄█▆▆▆▆▄▄▅▇	10.106	11.165	7.635	12.132	12.39	17.466	14.23	14.818	14.7	14.603	11.418	11.881	13.137	16.11
us-gaap:OtherLiabilitiesCurrent	▆▃██▅▇▄▄▁▃▂▄▁▃	3124000.0	2515000.0	3620000.0	3657000.0	3007000.0	3356000.0	2640000.0	2646000.0	1993000.0	2459000.0	2281000.0	2618000.0	2026000.0	2425000.0

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:LongTermDebt	██▇▇▃▃▂▂▂▁▁▁▁▁	241.83	238.466	234.397	231.82	173.634	168.466	162.904	151.104	151.276	149.005	147.852	144.294	144.421	144.1
us-gaap:LongTermDebtNoncurrent	███▇▃▃▂▁▁▁▁▁▁▁	237.939	234.789	230.777	228.272	163.574	158.422	152.851	141.083	142.129	140.061	139.045	135.806	136.429	136.156
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	▆▆▆▁▂▃▃▆▇▇█▆▆▇	33.731	34.157	34.671	27.826	29.31	29.976	30.661	33.882	35.128	36.041	36.686	33.544	34.651	35.738
us-gaap:OtherLiabilitiesNoncurrent	▇▇▇▇▇▇█▁▁▁▂▂▂▂	2480000.0	2500000.0	2546000.0	2567000.0	2612000.0	2530000.0	2730000.0	1199000.0	1250000.0	1250000.0	1315000.0	1348000.0	1378000.0	1410000.0

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:CommonStockValue	███▃▂▂▁▁▁▁▁▁▁▁	216.365	215.6	215.125	170.562	165.138	160.142	157.354	156.741	156.251	155.58	155.12	154.626	154.075	153.506
us-gaap:RetainedEarningsAccumulatedDeficit	█▇▇▆▅▅▄▄▃▂▂▂▁▁	117.008	111.8	108.667	105.233	98.146	94.0	91.433	88.413	79.826	74.854	74.055	72.403	68.249	66.354

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities	▁█▆▅▁▃▆▇▅▄▇▄▅▅	4.681	16.138	12.705	11.728	3.956	7.664	13.001	13.64	10.242	8.981	14.194	8.478	10.082	10.089
us-gaap:NetCashProvidedByUsedInInvestingActivities	▄▂▁▂▃▇▃▄▅█▅▆▇█	-20270000.0	-25147000.0	-27905000.0	-25522000.0	-23374000.0	-12324000.0	-22576000.0	-21141000.0	-18366000.0	-10011000.0	-16152000.0	-14005000.0	-11588000.0	-9577000.0
us-gaap:NetCashProvidedByUsedInFinancingActivities	▂▃▂█▃▂▂▂▂▁▂▂▁▁	4.42	15.811	4.621	66.712	16.79	5.787	9.701	7.206	11.182	-2.595	4.194	4.539	-0.397	1.201
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	▁█	-11.169	6.802	NA	NA	-2.628	1.127	NA	NA	NA	NA	NA	NA	NA	NA

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities	▁█▆▅▁▃▆▇▅▄▇▄▅▅	4.681	16.138	12.705	11.728	3.956	7.664	13.001	13.64	10.242	8.981	14.194	8.478	10.082	10.089
us-gaap:NetIncomeLoss	▆▄▄▇▄▃▃█▅▁▂▄▂▁	9.713	7.668	8.071	11.119	8.146	6.552	6.993	12.29	8.675	4.494	5.345	7.642	5.381	4.441
us-gaap:DepreciationDepletionAndAmortization	██▅▅▄▄▃▃▃▂▄▂▁▁	5.196	5.108	4.374	4.403	4.265	4.19	4.037	3.95	4.022	3.771	4.169	3.79	3.476	3.411
us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet	▄▃▆█▁▆▄▅▃▅▄▆▇▆	-653000.0	-1187000.0	106000.0	939000.0	-2075000.0	164000.0	-690000.0	-498000.0	-1105000.0	-296000.0	-605000.0	64000.0	723000.0	-13000.0
us-gaap:IncreaseDecreaseInAccountsReceivable	▇▂▁▇▇▁▁█▆▃▂▇▆▂	1796000.0	-1085000.0	-1499000.0	1651000.0	1774000.0	-1780000.0	-1782000.0	2533000.0	1041000.0	-815000.0	-945000.0	1777000.0	1107000.0	-1283000.0
us-gaap:DeferredIncomeTaxExpenseBenefit	▁▁▁▁▂▂▂▂▂▅▄█▇▅	-3.776	-3.43	-3.34	-3.304	-2.756	-2.319	-2.749	-3.215	-2.877	0.117	-0.45	3.999	3.378	1.017
us-gaap:ShareBasedCompensation	█▅▆▁█▆▇▆▇▅▅▆▆▅	470000.0	162000.0	228000.0	-294000.0	474000.0	229000.0	327000.0	222000.0	362000.0	173000.0	167000.0	236000.0	277000.0	160000.0

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities	▄▂▁▂▃▇▃▄▅█▅▆▇█	-20270000.0	-25147000.0	-27905000.0	-25522000.0	-23374000.0	-12324000.0	-22576000.0	-21141000.0	-18366000.0	-10011000.0	-16152000.0	-14005000.0	-11588000.0	-9577000.0
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment	▁█	20.27	25.147	NA	25.522	23.374	12.324	NA	21.141	18.366	10.011	NA	14.005	1.588	9.577

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities	▂▃▂█▃▂▂▂▂▁▂▂▁▁	4.42	15.811	4.621	66.712	16.79	5.787	9.701	7.206	11.182	-2.595	4.194	4.539	-0.397	1.201
us-gaap:ProceedsFromIssuanceOfLongTermDebt	▂▂▁█▂▂▃▂▂▂▂▂▁▂	4.323	5.398	-3.479	69.229	6.318	6.899	12.811	3.698	3.274	2.293	4.555	2.921	1.309	2.738
us-gaap:RepaymentsOfLongTermDebt	▁▂▁█▁▂▁█▁▁▁▆▁▁	0.958	1.33	1.028	3.959	1.019	1.337	1.011	3.869	1.003	1.141	0.996	3.048	0.989	1.126
us-gaap:PaymentsOfDividendsCommonStock	██▇▅▅▄▄▃▃▂▂▁▁▁	4.474	4.468	4.272	3.987	3.963	3.943	3.937	3.668	3.666	3.659	3.658	3.451	3.45	3.443

		2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
us-gaap:RepaymentsOfLongTermDebt	▁▂▁█▁▂▁█▁▁▁▆▁▁	0.958	1.33	1.028	3.959	1.019	1.337	1.011	3.869	1.003	1.141	0.996	3.048	0.989	1.126

Common Stock Value

us-gaap:CommonStockValue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	216	215	215	170	165	160	157	156	156	155	155	154	154	153	153	152	152	151	150	150	149	149	148	148	147	146	146	145	144	144	143	143	142	142	141	141	140	139
Percentage of CommonStockValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	22.8	23.1	23.6	19.2	20.4	20.5	20.5	20.8	21.4	22.1	23.5	23.7	24.1	24.5	24.7	24.9	25.3	25.8	25.8	24.9	25.5	25.7	25.8	27.3	27.4	27.6	27.6	26.3	26.2	26.4	25.6	26.1	26.2	26.5	26.3	27.8	28.0	28.5

Shares Outstanding

us-gaap:StatementEquityComponents

us-gaap:SharesOutstanding

us-gaap:CommonStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31	2009-12-31	2008-12-31
Value	17	17	17	16	16	16	16	16	16	16	16	16	0.016225	0.016124	0.015963	15	15	15	13	13
Percentage of SharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	17	17	17	16	16	16	16	16	16	16	16	16	16	16	16	16	16	0.01624	16	16	16	16	16	16	16	15	15	15	15	15	15	0.015752	0.01573	15	15	15	0.015611	0.015566
Percentage of CommonStockSharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Common Stock Shares Authorized

us-gaap:CommonStockSharesAuthorized

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	40	40	40	40	40	40	40	40	40	40	40	40	40	40	40	40	40	0.04	40	40	40	40	40	40	40	40	40	40	40	40	40	0.04	0.04	40	40	40	0.04	0.04
Percentage of CommonStockSharesAuthorized	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-09-30	2012-06-30	2012-03-31	2011-09-30	2011-06-30	2011-03-31	2010-09-30	2010-06-30
Value	17	17	16	16	16	16	16	16	16	16	0.016455	16	16	0.016389	16	16	16	16	16	16	16	16	16	16	15	0.015955	15	0.015861	0.015839	15	0.014235
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-09-30	2012-06-30	2012-03-31	2011-09-30	2011-06-30	2011-03-31	2010-09-30	2010-06-30
Value	17	17	16	16	16	16	16	16	16	16	0.016299	16	16	0.016233	16	16	16	16	16	15	15	15	15	15	15	0.015692	15	0.015598	0.015576	15	0.013972
Percentage of WeightedAverageNumberOfSharesOutstandingBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	0.55	0.44	0.46	0.67	0.49	0.4	0.43	0.75	0.53	0.27	0.32	0.47	0.33	0.27	0.2	0.54	0.36	0.29	0.29	0.41	0.31	0.22	0.23	0.42	0.29	0.2	0.2	0.36	0.28	0.2	0.17	0.39	0.23	0.11	0.12	0.33	0.23	0.17	0.15	0.37	0.31
Percentage of EarningsPerShareBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	0.55	0.44	0.46	0.66	0.49	0.39	0.43	0.74	0.52	0.27	0.32	0.46	0.33	0.27	0.19	0.54	0.36	0.29	0.28	0.41	0.31	0.22	0.22	0.42	0.29	0.2	0.19	0.36	0.28	0.2	0.17	0.38	0.23	0.11	0.12	0.32	0.23	0.17	0.16	0.36	0.31
Percentage of EarningsPerShareDiluted	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Revenue From Contract With Customer Including Assessed Tax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	35	31	32	37	33	30	33	38	34	31	31	36	32	30
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
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

Regulated And Unregulated Operating Revenue

us-gaap:RegulatedAndUnregulatedOperatingRevenue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	35	31	32	37	33	30	33	38	34	31	31	36	33	30	31	37	32	30	30	34	31	28	28	32	29	27	27	31	29	27	27	32	27	23	23	28	26	23	24	29	26
Percentage of RegulatedAndUnregulatedOperatingRevenue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 RevenueFromContractWithCustomerIncludingAssessedTax	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	100.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30
Value	-0.192	-0.129	-0.142	-0.251	-0.138	-0.125	-0.123	-0.219	-0.131	-0.129	-0.132	-0.22	-0.127	-0.112	-0.115	-0.144	-0.136	-0.104	-0.117	-0.116	-0.11	-0.117	-0.121	-0.169
Percentage of RegulatedAndUnregulatedOperatingRevenue	-0.5	-0.4	-0.4	-0.7	-0.4	-0.4	-0.4	-0.6	-0.4	-0.4	-0.4	-0.6	-0.4	-0.4	-0.4	-0.4	-0.4	-0.3	-0.4	-0.3	-0.3	-0.4	-0.4	-0.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	-0.5	-0.4	-0.4	-0.7	-0.4	-0.4	-0.4	-0.6	-0.4	-0.4	-0.4	-0.6	-0.4	-0.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	32	28	29	35	30	27	28	34	31	27	27	32	29	26	28	33	28	26	27	31	27	24	24	29	25	23	23	27	25	23	23	29	24	20	20	26	23
Percentage of RegulatedAndUnregulatedOperatingRevenue	91.5	91.1	90.8	92.7	91.2	90.9	86.9	89.4	89.3	87.3	87.2	89.2	88.7	87.9	88.7	89.9	88.2	88.1	88.1	89.8	88.3	86.5	88.4	89.8	88.1	87.0	87.0	89.4	88.1	86.6	87.3	89.9	89.2	88.6	89.2	91.6	89.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	91.6	91.2	90.9	92.8	91.3	91.0	87.0	89.5	89.3	87.4	87.3	89.2	88.8	88.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	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 RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RegulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:UnregulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	3.18	2.961	3.145	3.02	3.087	2.925	4.492	4.304	3.882	4.1	4.157	4.142	3.863	3.75	3.703	3.949	4.002	3.734	3.793	3.65	3.804	3.992	3.391	3.492	3.624	3.637	3.676	3.47	3.58	3.736	3.563	3.441	3.089	2.758	2.585	2.605	2.774
Percentage of RegulatedAndUnregulatedOperatingRevenue	9.0	9.3	9.6	8.0	9.2	9.5	13.5	11.1	11.1	13.2	13.2	11.5	11.7	12.4	11.6	10.4	12.2	12.2	12.3	10.5	12.0	13.9	12.1	10.7	12.4	13.4	13.4	11.1	12.3	13.8	13.2	10.6	11.3	11.7	11.1	9.1	10.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	9.0	9.3	9.6	8.0	9.3	9.5	13.5	11.1	11.1	13.2	13.2	11.5	11.7	12.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:UnregulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Operating Expenses

us-gaap:OperatingExpenses

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	25	25	25	25	24	23	26	25	24	24	22	23	23	22	23	23	22	22	22	23	22	22	20	21	20	21	20	21	20	21	21	21	20	19	19	20	19	19	19	19	18
Percentage of OperatingExpenses	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 RevenueFromContractWithCustomerIncludingAssessedTax	73.5	79.5	77.0	68.3	73.3	77.2	78.6	66.7	69.4	79.7	73.2	64.7	71.1	74.3	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Operating Income Loss

us-gaap:OperatingIncomeLoss

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	9.385	6.527	7.559	11	8.95	7.028	7.153	12	10	6.35	8.471	12	9.563	7.78	7.846	14	10	8.302	8.46	11	9.235	6.685	8.058	11	8.747	5.967	6.664	10	8.171	5.865	5.717	10	7.21	3.877	4.179	8.516	6.738	4.768	5.393	10	7.894
Percentage of OperatingIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	26.6	20.6	23.1	31.8	26.8	22.9	21.5	33.4	30.7	20.4	27.0	35.4	29.0	25.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	8.639	5.843	6.868	11	7.903	6.034	6.3	12	9.988	5.625	7.757	12	8.877	7.22	7.261	13	9.694	7.733	7.829	10	8.672	6.165	7.415	11	8.143	5.404	6.045	9.685	7.678	5.338	5.146	10	6.878	3.503	3.867	8.241	6.317
Percentage of OperatingIncomeLoss	92.1	89.5	90.9	91.8	88.3	85.9	88.1	94.6	93.2	88.6	91.6	94.5	92.8	92.8	92.5	95.5	93.9	93.1	92.5	95.4	93.9	92.2	92.0	95.0	93.1	90.6	90.7	94.3	94.0	91.0	90.0	96.1	95.4	90.4	92.5	96.8	93.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	24.5	18.4	21.0	29.2	23.7	19.7	19.0	31.6	28.6	18.1	24.7	33.5	26.9	24.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	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 RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RegulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:UnregulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	0.746	0.684	0.69	0.982	1.047	0.994	0.853	0.704	0.733	0.725	0.714	0.708	0.686	0.56	0.586	0.64	0.634	0.569	0.633	0.522	0.563	0.52	0.644	0.581	0.604	0.563	0.619	0.585	0.493	0.527	0.571	0.426	0.332	0.374	0.312	0.275	0.421
Percentage of OperatingIncomeLoss	7.9	10.5	9.1	8.2	11.7	14.1	11.9	5.4	6.8	11.4	8.4	5.5	7.2	7.2	7.5	4.5	6.1	6.9	7.5	4.6	6.1	7.8	8.0	5.0	6.9	9.4	9.3	5.7	6.0	9.0	10.0	3.9	4.6	9.6	7.5	3.2	6.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	2.1	2.2	2.1	2.6	3.1	3.2	2.6	1.8	2.1	2.3	2.3	2.0	2.1	1.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:UnregulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Interest Expense

us-gaap:InterestExpense

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	1946000.0	1669000.0	2280000.0	1996000.0	1788000.0	1200000.0	1829000.0	1723000.0	2068000.0	1138000.0	1541000.0	1493000.0	1469000.0	1003000.0	1452000.0	1427000.0	1436000.0	978000.0	1496000.0	1505000.0	1496000.0	1058000.0	1473000.0	1516000.0	1515000.0	1103000.0	1573000.0	1541000.0	1538000.0	1155000.0	1784000.0	1808000.0	1779000.0	1354000.0	1745000.0	1703000.0	1714000.0	1214000.0	1800000.0	1819000.0	1882000.0
Percentage of InterestExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	5.5	5.3	7.0	5.3	5.4	3.9	5.5	4.5	5.9	3.7	4.9	4.1	4.5	3.3	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	2015-09-30	2014-09-30
Value	334000.0	385000.0	-512000.0	-4000.0	-80000.0	-57000.0	353000.0	409000.0	571000.0	297000.0	846000.0	43000.0	47000.0	6000.0	-1600000.0	400000.0	25000.0	48000.0	108000.0	5000.0
Percentage of OtherNonoperatingIncomeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	0.9	1.2	-1.6	-0.0	-0.2	-0.2	1.1	1.1	1.6	1.0	2.7	0.1	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	8.568	6.366	5.882	10	7.725	6.286	6.234	12	9.438	5.676	7.183	11	8.299	6.897	4.697	13	9.029	7.415	6.854	10	7.867	5.682	5.993	10	7.278	4.922	4.849	8.859	6.711	4.835	4.139	9.247
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	24.3	20.1	18.0	28.8	23.2	20.5	18.8	31.1	27.1	18.2	22.9	31.9	25.2	22.9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	1129000.0	1508000.0	604000.0	867000.0	563000.0	458000.0	910000.0	833000.0	785000.0	464000.0	253000.0	217000.0	205000.0	120000.0	-1698000.0	607000.0	137000.0	91000.0	-112000.0	221000.0	128000.0	55000.0	-593000.0	85000.0	46000.0	58000.0	-242000.0	130000.0	78000.0	125000.0	206000.0	212000.0	251000.0	188000.0	585000.0	974000.0	288000.0	302000.0	308000.0	186000.0
Percentage of NonoperatingIncomeExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	3.2	4.8	1.8	2.3	1.7	1.5	2.7	2.2	2.3	1.5	0.8	0.6	0.6	0.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	-1.145	-1.302	-2.188	-0.265	-0.421	-0.266	-0.759	-0.262	0.763	1.182	1.837	3.888	2.918	2.456	1.477	4.523	3.11	2.625	2.293	3.433	2.778	2.046	2.202	3.431	2.55	1.753	1.681	3.052	2.23	1.658	1.413	3.109	1.957	0.904	0.97	2.644	1.687	1.226	1.291	2.652	2.092
Percentage of IncomeTaxExpenseBenefit	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	-3.2	-4.1	-6.7	-0.7	-1.3	-0.9	-2.3	-0.7	2.2	3.8	5.8	10.8	8.8	8.2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Income Taxes Paid Net

us-gaap:IncomeTaxesPaidNet

Period End	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	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2014-12-31	2014-09-30	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	0.375	0.002	3.587	0.91	5.027	0.815	1.498	1.202	1.292	0.748	1.718	0.88	3.13	0.001	0.255	0.235	2.128	1.56	1.84	1.979	2.06	1.13	1.036
Percentage of IncomeTaxesPaidNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 RevenueFromContractWithCustomerIncludingAssessedTax	1.1	0.0	11.0	2.4	15.1	2.7	4.5	3.1	4.1	2.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss

us-gaap:NetIncomeLoss

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31
Value	9.713	7.668	8.071	11	8.146	6.552	6.993	12	8.675	4.494	5.345	7.642	5.381	4.441	3.22	8.813	5.919	4.79	4.56	6.743	5.089	3.636	3.79	6.758	4.728	3.169	3.168	5.807	4.481	3.177	2.726	6.138	3.725	1.807
Percentage of NetIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	27.6	24.2	24.7	29.5	24.4	21.4	21.0	31.8	24.9	14.4	17.0	21.1	16.3	14.8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	9.192	7.181	7.902	10	7.423	5.868	6.501	11	8.151	3.983	5.106	7.232	4.972	4.139	4.127	8.154	5.583	4.492	4.236	6.466	4.809	3.377	3.496	6.458	4.416	2.881	2.856	5.505	4.235	2.91	2.43	5.926
Percentage of NetIncomeLoss	94.6	93.6	97.9	93.6	91.1	89.6	93.0	95.8	94.0	88.6	95.5	94.6	92.4	93.2	128.2	92.5	94.3	93.8	92.9	95.9	94.5	92.9	92.2	95.6	93.4	90.9	90.2	94.8	94.5	91.6	89.1	96.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	26.1	22.6	24.2	27.6	22.3	19.1	19.6	30.4	23.4	12.8	16.3	20.0	15.1	13.8	0.0	0.0	0.0	0.0	0.0	0.0	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 RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RegulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:UnregulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	0.521	0.487	0.168	0.71	0.723	0.684	0.492	0.52	0.524	0.511	0.24	0.41	0.409	0.302	-0.907	0.659	0.336	0.298	0.325	0.277	0.28	0.259	0.295	0.3	0.312	0.288	0.312	0.302	0.246	0.267	0.296	0.212
Percentage of NetIncomeLoss	5.4	6.4	2.1	6.4	8.9	10.4	7.0	4.2	6.0	11.4	4.5	5.4	7.6	6.8	-28.2	7.5	5.7	6.2	7.1	4.1	5.5	7.1	7.8	4.4	6.6	9.1	9.8	5.2	5.5	8.4	10.9	3.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	1.5	1.5	0.5	1.9	2.2	2.2	1.5	1.3	1.5	1.6	0.8	1.1	1.2	1.0	0.0	0.0	0.0	0.0	0.0	0.0	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 RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:UnregulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	2020-06-30	2020-03-31	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	9.713	7.668	8.07	11	8.146	6.552	6.993	12	8.675	4.494
Percentage of NetIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	27.6	24.2	24.7	29.5	24.4	21.4	21.0	31.8	24.9	14.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RetainedEarnings	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Preferred Stock Dividends Income Statement Impact

us-gaap:PreferredStockDividendsIncomeStatementImpact

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	30000.0	30000.0	30000.0	30000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	43000.0	43000.0	44000.0	51000.0	52000.0	51000.0	52000.0	51000.0	52000.0	51000.0	52000.0	51000.0	52000.0	51000.0	52000.0
Percentage of PreferredStockDividendsIncomeStatementImpact	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 RevenueFromContractWithCustomerIncludingAssessedTax	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	9.683	7.638	8.04	11	8.11	6.516	6.957	12	8.639	4.458	5.31	7.606	5.345	4.405	3.184	8.777	5.883	4.754	4.525	6.707	5.053	3.6	3.755	6.722	4.692	3.126	3.125	5.763	4.43	3.125	2.675	6.086	3.674	1.755	1.998	5.091	3.574	2.578	2.559	5.684	4.372
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	27.5	24.1	24.6	29.4	24.3	21.3	20.9	31.7	24.8	14.3	16.9	21.0	16.2	14.6	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss Available To Common Stockholders Diluted

us-gaap:NetIncomeLossAvailableToCommonStockholdersDiluted

Period End	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	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	9.7	8.057	11	8.133	6.539	6.98	12	8.662	4.481	5.333	7.629	5.368	4.428	3.207	8.8	5.906	4.777	4.548	6.73	5.076	3.623	3.778	6.745	4.715	3.156	3.155	5.793	4.468	3.163	2.713	6.124	3.712	1.793	2.036	5.129	3.612
Percentage of NetIncomeLossAvailableToCommonStockholdersDiluted	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 RevenueFromContractWithCustomerIncludingAssessedTax	27.5	24.6	29.4	24.4	21.3	21.0	31.7	24.8	14.4	17.0	21.1	16.3	14.7	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	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Assets

us-gaap:Assets

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	950	935	909	887	807	782	767	752	729	705	661	651	638	627	620	612	600	585	584	603	586	579	575	542	538	530	530	553	552	546	561	548	545	536	537	507	502	489
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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
Value	-12.983	1.462	-9.889	-8.52	-8.543	-6.431	-5.913	-8.461	-9.667	-7.474	-7.769	-9.101	-10.677	-9.257	-5.999	-5.999	-4.199	-4.199	-6.374	-4.364	-6.334
Percentage of Assets	-1.4	0.2	-1.1	-1.0	-1.1	-0.8	-0.8	-1.1	-1.3	-1.1	-1.2	-1.4	-1.7	-1.5	-1.0	-1.0	-0.7	-0.7	-1.1	-0.7	-1.1
Percentage of Assets	-1.4	0.2	-1.1	-1.0	-1.1	-0.8	-0.8	-1.1	-1.3	-1.1	-1.2	-1.4	-1.7	-1.5	-1.0	-1.0	-0.7	-0.7	-1.1	-0.7	-1.1
Percentage of Assets us-gaap:IntersegmentElimination	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	953	924	910	886	807	780	764	754	732	705	661	654	642	629	619	611	597	582	584	600	582	578	574	540	537	529	529	555	551	545	560	546	544	539
Percentage of Assets	100.3	98.8	100.0	99.9	99.9	99.7	99.6	100.2	100.4	100.1	100.1	100.4	100.6	100.4	100.0	99.8	99.5	99.4	100.0	99.6	99.4	99.7	99.8	99.7	99.8	99.8	99.8	100.4	99.7	99.8	99.7	99.8	99.9	100.4
Percentage of Assets	100.3	98.8	100.0	99.9	99.9	99.7	99.6	100.2	100.4	100.1	100.1	100.4	100.6	100.4	100.0	99.8	99.5	99.4	100.0	99.6	99.4	99.7	99.8	99.7	99.8	99.8	99.8	100.4	99.7	99.8	99.7	99.8	99.9	100.4
Percentage of Assets us-gaap:RegulatedOperation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:UnregulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2011-12-31
Value	10	9.378	9.686	9.593	9.093	9.087	8.994	6.95	6.819	6.987	7.093	6.772	6.681	6.85	6.245	7.047	7.398	7.754	6.436	6.991	8.15	8.05	7.252	8.262	7.831	9.033	8.887	8.106	11	11	11	11	10	10
Percentage of Assets	1.1	1.0	1.1	1.1	1.1	1.2	1.2	0.9	0.9	1.0	1.1	1.0	1.0	1.1	1.0	1.2	1.2	1.3	1.1	1.2	1.4	1.4	1.3	1.5	1.5	1.7	1.7	1.5	2.1	2.0	2.1	2.1	2.0	1.9
Percentage of Assets	1.1	1.0	1.1	1.1	1.1	1.2	1.2	0.9	0.9	1.0	1.1	1.0	1.0	1.1	1.0	1.2	1.2	1.3	1.1	1.2	1.4	1.4	1.3	1.5	1.5	1.7	1.7	1.5	2.1	2.0	2.1	2.1	2.0	1.9
Percentage of Assets us-gaap:UnregulatedOperation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31
Value	950	935	909	887	807	782	767	752	729	705	661	651	638	627	620	612	600	585	584	603	586	579	575	542	538	530	530	553	552	546	561	548	545	536	537	507	489
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Assets Current

us-gaap:AssetsCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	43	40	29	34	32	29	30	35	31	25	29	30	29	27	26	30	28	24	24	30	29	25	22	28	28	25	25	27	26	25	24	25	23	19	22	27	25	22
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	100.0	100.0	100.0	100.0	100.0	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	4.6	4.3	3.2	3.9	4.0	3.8	4.0	4.7	4.3	3.6	4.4	4.6	4.7	4.3	4.3	5.0	4.7	4.2	4.2	5.1	5.0	4.4	4.0	5.3	5.3	4.8	4.9	4.9	4.7	4.6	4.4	4.7	4.3	3.6	4.3	5.5	5.1	4.7

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30	2009-12-31	2008-12-31
Value	13	15	2.23	3.151	2.99	4.986	3.705	3.579	2.673	1.994	4.937	2.701	3.689	5.592	3.879	1.453	1.229	3.646	3.469	4.651	5.774	5.046	2.673	5.052	5.071	5.902	4.834	2.937	2.992	4.508	3.025	1.798	2.727	0.854	3.106	4.134	4.283	2.453	2.453	3.09	4.038	4.278	3.288
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	100.0	100.0	100.0	100.0	100.0	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	1.4	1.6	0.2	0.4	0.4	0.6	0.5	0.5	0.4	0.3	0.7	0.4	0.6	0.9	0.6	0.2	0.2	0.6	0.6	0.8	1.0	0.9	0.5	0.9	0.9	1.1	0.9	0.5	0.5	0.8	0.5	0.3	0.5	0.2	0.6	0.8	0.9	0.0	0.5	0.0	0.0	0.0	0.0

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	12	10	11	13	11	9.982	11	13	11	9.97	10	11	9.953	8.846	10	13	10	9.53	10	12	10	10	10	11	11	10	11	12	11	11	12	13	10	10	11	13	10	11
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	100.0	100.0	100.0	100.0	100.0	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	1.3	1.2	1.3	1.5	1.5	1.3	1.5	1.8	1.5	1.4	1.6	1.8	1.6	1.4	1.6	2.2	1.8	1.6	1.7	2.1	1.8	1.8	1.7	2.1	2.1	2.0	2.2	2.3	2.1	2.1	2.2	2.4	1.9	2.0	2.1	2.6	2.1	2.4

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	5573000.0	5757000.0	5944000.0	6133000.0	6323000.0	6517000.0
Percentage of OperatingLeaseRightOfUseAsset	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	0.6	0.6	0.7	0.7	0.8	0.8

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	1408000.0	1837000.0	1899000.0	1954000.0	1983000.0	2010000.0	2093000.0	94000.0	435000.0	148000.0	177000.0	196000.0	226000.0	252000.0	293000.0	311000.0	343000.0	341000.0	385000.0	433000.0	453000.0	483000.0	518000.0	683000.0	703000.0	714000.0	727000.0	731000.0	390000.0	408000.0	448000.0	432000.0	594000.0	647000.0	630000.0	622000.0	579000.0	387000.0
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	100.0	100.0	100.0	100.0	100.0	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	0.1	0.2	0.2	0.2	0.2	0.3	0.3	0.0	0.1	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1

Liabilities Current

us-gaap:LiabilitiesCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	84	80	64	103	102	93	94	94	81	64	64	59	55	49	47	44	39	30	28	46	49	43	43	56	54	52	52	52	52	51	55	49	48	45	46	48	43	40
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	100.0	100.0	100.0	100.0	100.0	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	8.9	8.6	7.1	11.7	12.7	11.9	12.3	12.5	11.2	9.1	9.8	9.1	8.7	7.9	7.6	7.3	6.5	5.2	4.8	7.8	8.4	7.5	7.6	10.4	10.1	9.9	9.9	9.5	9.4	9.5	10.0	9.1	8.9	8.6	8.7	9.5	8.7	8.3

Notes Payable Current

us-gaap:NotesPayableCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	37	33	20	58	59	49	48	48	39	27	28	24	17	14	12	13	10	2.0	3.0	18	18	15	19	30	28	27	28	30	27
Percentage of NotesPayableCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	3.9	3.6	2.2	6.6	7.4	6.3	6.3	6.4	5.3	3.9	4.2	3.8	2.7	2.3	1.9	2.2	1.7	0.3	0.5	3.0	3.1	2.6	3.3	5.6	5.2	5.2	5.4	5.5	5.0

Long Term Debt Current

us-gaap:LongTermDebtCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	7.34	7.171	7.178	7.161	7.353	7.336	7.343	7.327	7.236	6.982	6.865	6.547	6.164	6.148	6.159	6.144	5.869	5.691	5.739	5.725	5.692	6.092	5.91	5.634	5.52	5.377	5.386	5.373	5.285	5.122	11	5.064	4.996	4.739	4.569	4.564	4.448	4.432
Percentage of LongTermDebtCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	0.8	0.8	0.8	0.8	0.9	0.9	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	1.0	0.9	1.0	1.1	1.0	1.0	1.0	1.0	1.0	1.0	1.0	0.9	2.0	0.9	0.9	0.9	0.8	0.9	0.9	0.9

Accounts Payable Current

us-gaap:AccountsPayableCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	22	24	23	20	18	13	19	19	16	11	13	12	15	8.987	12	10	9.589	6.5	6.525	8.609	8.925	6.954	6.354	7.193	6.675	5.595	6.328	4.374	5.133	4.526	3.808	4.242	4.797	4.826	5.706	5.789	5.704	6.403
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	100.0	100.0	100.0	100.0	100.0	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	2.4	2.6	2.6	2.3	2.2	1.8	2.5	2.6	2.2	1.6	2.1	1.9	2.4	1.4	2.0	1.7	1.6	1.1	1.1	1.4	1.5	1.2	1.1	1.3	1.2	1.1	1.2	0.8	0.9	0.8	0.7	0.8	0.9	0.9	1.1	1.1	1.1	1.3

Accrued Income Taxes Current

us-gaap:AccruedIncomeTaxesCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	10	11	7.635	12	12	17	14	14	14	14	11	11	13	16	12	10	9.439	12	9.126	11	12	12	8.948	10	9.952	11	8.132	9.224	9.796	11	9.266	9.24	9.252	10	7.847	10	9.237	8.752
Percentage of AccruedIncomeTaxesCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	1.1	1.2	0.8	1.4	1.5	2.2	1.9	2.0	2.0	2.1	1.7	1.8	2.1	2.6	2.0	1.7	1.6	2.2	1.6	1.9	2.1	2.2	1.6	1.9	1.8	2.1	1.5	1.7	1.8	2.1	1.6	1.7	1.7	1.9	1.5	2.1	1.8	1.8

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31
Value	3124000.0	2515000.0	3620000.0	3657000.0	3007000.0	3356000.0	2640000.0	2646000.0	1993000.0	2459000.0	2281000.0	2618000.0	2026000.0	2425000.0	2162000.0	2403000.0	1735000.0	2159000.0	1945000.0	1946000.0	2318000.0	1752000.0	1687000.0	1518000.0	2399000.0	1563000.0	2394000.0	1673000.0	1950000.0	1416000.0	2067000.0	1489000.0	1875000.0	1400000.0	1953000.0	1412000.0	1691000.0
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	100.0	100.0	100.0	100.0	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	0.3	0.3	0.4	0.4	0.4	0.4	0.3	0.4	0.3	0.3	0.3	0.4	0.3	0.4	0.3	0.4	0.3	0.4	0.3	0.3	0.4	0.3	0.3	0.3	0.4	0.3	0.5	0.3	0.4	0.3	0.4	0.3	0.3	0.3	0.4	0.3	0.3

Long Term Debt

us-gaap:LongTermDebt

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2010-12-31
Value	241	238	234	231	173	168	162	151	151	149	147	144	144	144	142	138	138	138	140	139	139	142	140	132	135	132	133	133	133	130	131	132	135	131	132	132	133
Percentage of LongTermDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	25.4	25.5	25.8	26.1	21.5	21.5	21.2	20.1	20.7	21.1	22.4	22.1	22.6	23.0	23.0	22.7	23.1	23.7	24.0	23.1	23.9	24.5	24.3	24.5	25.2	24.9	25.1	24.2	24.2	23.9	23.4	24.2	24.8	24.6	24.6	26.2	27.4

us-gaap:DebtInstrument

msex:FirstMortgage10

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.621	0.621	0.632	0.633	0.71	0.71	0.723	0.723	0.799	0.799	0.813	0.813	0.887	0.887	0.903	0.903	0.976	0.976	0.993	0.993	1.064	1.064	1.083	1.083	1.152	1.152	1.171	1.171	1.262
Percentage of LongTermDebt	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.8	0.7	0.8	0.8	0.8	0.9	0.9	0.9	1.0
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage10	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage11

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.71	0.71	0.71	0.71	0.795	0.795	0.795	0.795	0.88	0.88	0.88	0.88	0.96	0.96	0.96	0.96	1.02	1.02	1.3	1.3	1.39	1.39	1.39	1.39	1.475	1.475	1.475	1.475	1.56
Percentage of LongTermDebt	0.3	0.3	0.3	0.3	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.7	0.9	0.9	1.0	1.0	1.0	1.0	1.1	1.1	1.1	1.1	1.2
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3
Percentage of Assets msex:FirstMortgage11	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage12

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.416	0.416	0.429	0.429	0.506	0.506	0.52	0.52	0.594	0.594	0.61	0.61	0.683	0.683	0.7	0.7	0.771	0.771	0.789	0.789	0.861	0.861	0.881	0.881	0.95	0.95	0.971	0.971	1.06
Percentage of LongTermDebt	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.8
Percentage of Assets	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage12	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage13

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.588	0.588	0.588	0.588	0.671	0.671	0.671	0.671	0.75	0.75	0.75	0.75	0.824	0.824	0.824	0.824	0.904	0.904	1.01	1.01	1.09	1.09	1.09	1.09	1.165	1.165	1.165	1.165	1.235
Percentage of LongTermDebt	0.2	0.2	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8	0.9	0.9	0.9	0.9	0.9
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage13	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage14

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.79	0.791	0.807	0.807	0.88	0.88	0.898	0.898	0.969	0.969	0.988	0.988	1.058	1.058	1.078	1.078	1.146	1.146	1.167	1.167	1.233	1.233	1.255	1.255	1.322	1.322	1.346	1.346	1.435
Percentage of LongTermDebt	0.3	0.3	0.3	0.3	0.5	0.5	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8	0.8	0.8	0.9	0.9	0.9	0.9	1.0	1.0	1.0	1.0	1.1
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.2	0.3
Percentage of Assets msex:FirstMortgage14	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage15

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.928	0.928	0.928	0.928	1.01	1.01	1.01	1.01	1.095	1.095	1.095	1.095	1.175	1.175	1.175	1.175	1.25	1.365	1.365	1.365	1.435	1.435	1.435	1.435	1.505	1.505	1.505	1.505	1.57
Percentage of LongTermDebt	0.4	0.4	0.4	0.4	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8	0.8	0.9	1.0	1.0	1.0	1.0	1.0	1.0	1.1	1.1	1.1	1.1	1.1	1.2
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3
Percentage of Assets msex:FirstMortgage15	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage16

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1.003	1.003	1.037	1.037	1.103	1.103	1.137	1.137	1.203	1.203	1.237	1.237	1.304	1.304	1.337	1.337	1.404	1.404	1.437	1.437	1.504	1.504	1.537	1.537	1.604	1.604	1.637	1.637	1.801
Percentage of LongTermDebt	0.4	0.4	0.4	0.4	0.6	0.7	0.7	0.8	0.8	0.8	0.8	0.9	0.9	0.9	0.9	1.0	1.0	1.0	1.0	1.0	1.1	1.1	1.1	1.2	1.2	1.2	1.2	1.2	1.4
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3
Percentage of Assets msex:FirstMortgage16	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage17

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1.19	1.19	1.19	1.19	1.285	1.415	1.415	1.415	1.505	1.505	1.505	1.505	1.59	1.59	1.59	1.59	1.675	1.675	1.675	1.675	1.755	1.755	1.755	1.755	1.835	1.835	1.835	1.835	1.91
Percentage of LongTermDebt	0.5	0.5	0.5	0.5	0.7	0.8	0.9	0.9	1.0	1.0	1.0	1.0	1.1	1.1	1.1	1.1	1.2	1.2	1.2	1.2	1.3	1.2	1.3	1.3	1.4	1.4	1.4	1.4	1.5
Percentage of Assets	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3
Percentage of Assets msex:FirstMortgage17	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage18

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1.756	1.756	1.806	1.806	1.906	1.906	1.956	1.957	2.057	2.057	2.107	2.107	2.207	2.207	2.258	2.258	2.358	2.358	2.408	2.408	2.508	2.508	2.559	2.559	2.659	2.659	2.709	2.709	2.86
Percentage of LongTermDebt	0.7	0.7	0.8	0.8	1.1	1.1	1.2	1.3	1.4	1.4	1.4	1.5	1.5	1.5	1.6	1.6	1.7	1.7	1.7	1.7	1.8	1.8	1.8	1.9	2.0	2.0	2.0	2.0	2.2
Percentage of Assets	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5
Percentage of Assets msex:FirstMortgage18	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage19

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.66	0.66	0.66	0.66	0.7	0.7	0.7	0.7	0.74	0.74	0.74	0.74	0.78	0.78	0.78	0.78	0.815	0.815	0.815	0.815	0.85	0.85	0.85	0.85	0.885	0.885	0.885	0.885	0.915
Percentage of LongTermDebt	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage19	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage23

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	1.906	1.906	1.957	1.957	2.057	2.057	2.107	2.107	2.208	2.208	2.258	2.258	2.358	2.358	2.408	2.408	2.508	2.509	2.559	2.559	2.659	2.659	2.709	2.709	2.809	2.809	2.86	2.86
Percentage of LongTermDebt	0.8	0.8	0.8	0.8	1.2	1.2	1.3	1.4	1.5	1.5	1.5	1.6	1.6	1.6	1.7	1.7	1.8	1.8	1.8	1.8	1.9	1.9	1.9	2.0	2.1	2.1	2.1	2.1
Percentage of Assets	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5
Percentage of Assets msex:FirstMortgage23	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage24

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30
Value	0.755	0.755	0.755	0.755	0.8	0.8	0.8	0.8	0.845	0.845	0.845	0.845	0.89	0.89	0.89	0.89	0.935	0.935	0.935	0.935	0.975	0.975	0.975	0.975	1.015	1.015	1.015	1.015
Percentage of LongTermDebt	0.3	0.3	0.3	0.3	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.7	0.8	0.8	0.8
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage24	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage25

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30
Value	1.956	1.956	2.004	2.003	2.099	2.1	2.147	2.147	2.243	2.243	2.29	2.29	2.386	2.386	2.433	2.433	2.529	2.529	2.577	2.577	2.672	2.672	2.72	2.72	2.815
Percentage of LongTermDebt	0.8	0.8	0.9	0.9	1.2	1.2	1.3	1.4	1.5	1.5	1.5	1.6	1.7	1.7	1.7	1.8	1.8	1.8	1.8	1.9	1.9	1.9	1.9	2.0	2.1
Percentage of Assets	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5
Percentage of Assets msex:FirstMortgage25	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage26

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30
Value	0.755	0.755	0.755	0.755	0.795	0.795	0.795	0.795	0.83	0.83	0.83	0.83	0.865	0.865	0.865	0.865	0.9	0.9	0.9	0.9	0.935	0.935	0.935	0.935	0.935
Percentage of LongTermDebt	0.3	0.3	0.3	0.3	0.5	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.1	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage26	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage27

Period End	2020-06-30	2020-03-31	2019-12-31	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	10	10	10	10	10	10	11	11	11	11	11
Percentage of LongTermDebt	4.3	4.4	4.5	4.6	6.3	6.5	6.8	7.3	7.4	7.6	7.6
Percentage of Assets	1.1	1.1	1.2	1.2	1.3	1.4	1.4	1.5	1.5	1.6	1.7
Percentage of Assets msex:FirstMortgage27	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage28

Period End	2020-06-30	2020-03-31	2019-12-31	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	3.785	3.785	3.785	3.785	3.86	3.86	3.86	3.86	3.86	3.86	3.86
Percentage of LongTermDebt	1.6	1.6	1.6	1.6	2.2	2.3	2.4	2.6	2.6	2.6	2.6
Percentage of Assets	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5	0.6
Percentage of Assets msex:FirstMortgage28	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage29

Period End	2020-06-30	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	6.599	6.599	6.678	6.678	6.837	6.837	6.917	6.917	7.076
Percentage of LongTermDebt	2.7	2.8	2.8	2.9	3.9	4.1	4.2	4.6	4.7
Percentage of Assets	0.7	0.7	0.7	0.8	0.8	0.9	0.9	0.9	1.0
Percentage of Assets msex:FirstMortgage29	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage31

Period End	2020-06-30	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	2.32	2.32	32	2.32	2.365	2.365	2.365	2.365	2.365
Percentage of LongTermDebt	1.0	1.0	13.9	1.0	1.4	1.4	1.5	1.6	1.6
Percentage of Assets	0.2	0.2	3.6	0.3	0.3	0.3	0.3	0.3	0.3
Percentage of Assets msex:FirstMortgage31	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage32

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30
Value	32	32	21	32
Percentage of LongTermDebt	13.4	13.6	9.0	14.0
Percentage of Assets	3.4	3.5	2.3	3.7
Percentage of Assets msex:FirstMortgage32	0.0	0.0	0.0	0.0

msex:FirstMortgage5

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.235	0.235	0.241	0.241	0.354	0.354	0.362	0.362	0.471	0.471	0.482	0.482	0.59	0.59	0.603	0.603	0.708	0.708	0.723	0.723	0.827	0.827	0.845	0.845	0.945	0.945	0.965	0.965	1.085
Percentage of LongTermDebt	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage6

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.331	0.331	0.331	0.331	0.489	0.489	0.489	0.489	0.636	0.636	0.636	0.636	0.779	0.779	0.779	0.779	0.875	0.875	0.895	0.895	1.025	1.025	1.025	1.025	1.145	1.145	1.145	1.145	1.275
Percentage of LongTermDebt	0.1	0.1	0.1	0.1	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.8	0.8	0.9	0.9	0.9	1.0
Percentage of Assets	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
Percentage of Assets msex:FirstMortgage6	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage8

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1.407	1.407	1.456	1.455	1.818	1.819	1.876	1.876	2.231	2.231	2.296	2.296	2.641	2.641	2.713	2.713	3.055	3.055	3.132	3.132	3.468	3.468	3.55	3.55	3.882	3.882	3.968	3.968	4.386
Percentage of LongTermDebt	0.6	0.6	0.6	0.6	1.0	1.1	1.2	1.2	1.5	1.5	1.6	1.6	1.8	1.8	1.9	2.0	2.2	2.2	2.2	2.2	2.5	2.4	2.5	2.7	2.9	2.9	3.0	3.0	3.3
Percentage of Assets	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.8
Percentage of Assets msex:FirstMortgage8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:FirstMortgage9

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	2.44	2.44	2.44	2.44	2.98	2.98	2.98	2.98	3.495	3.495	3.495	3.495	3.69	3.69	3.69	3.69	3.69	3.69	3.69	3.69	3.69	4.9	4.9	4.9	5.335	5.335	5.335	5.335	5.755
Percentage of LongTermDebt	1.0	1.0	1.0	1.1	1.7	1.8	1.8	2.0	2.3	2.3	2.4	2.4	2.6	2.6	2.6	2.7	2.7	2.7	2.6	2.7	2.6	3.4	3.5	3.7	3.9	4.0	4.0	4.0	4.4
Percentage of Assets	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.6	0.8	0.9	0.9	1.0	1.0	1.0	1.0	1.0
Percentage of Assets msex:FirstMortgage9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:NewConstructionLoans

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30
Value	49	45	40	38	29	23	16	3.698	6.167	3.874	14	11	10	7.47	2.788
Percentage of LongTermDebt	20.6	19.1	17.3	16.5	17.1	13.9	10.1	2.4	4.1	2.6	10.0	8.0	7.1	5.2	2.0
Percentage of Assets	5.2	4.9	4.4	4.3	3.7	3.0	2.2	0.5	0.9	0.6	2.2	1.8	1.6	1.2	0.5
Percentage of Assets msex:NewConstructionLoans	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt1

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	3.325	3.43	3.535	3.64	3.745	3.85	3.955	4.06	4.165	4.27	4.375	4.48	4.585	4.69	4.795	4.9	5.005	5.11	5.215	5.32	5.425	5.53	5.635	5.74	5.845	5.95	6.055	6.16	6.475
Percentage of LongTermDebt	1.4	1.4	1.5	1.6	2.2	2.3	2.4	2.7	2.8	2.9	3.0	3.1	3.2	3.3	3.4	3.5	3.6	3.7	3.7	3.8	3.9	3.9	4.0	4.3	4.3	4.5	4.5	4.6	4.9
Percentage of Assets	0.3	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.9	0.9	0.9	0.9	1.0	1.0	1.1	1.1	1.1	1.1	1.1	1.2
Percentage of Assets msex:SecuredDebt1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt2

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	2.847	2.917	2.987	3.057	3.127	3.197	3.267	3.337	3.407	3.477	3.547	3.617	3.687	3.757	3.827	3.897	3.967	4.037	4.107	4.177	4.247	4.317	4.387	4.457	4.527	4.597	4.667	4.737	4.947
Percentage of LongTermDebt	1.2	1.2	1.3	1.3	1.8	1.9	2.0	2.2	2.3	2.3	2.4	2.5	2.6	2.6	2.7	2.8	2.9	2.9	2.9	3.0	3.0	3.0	3.1	3.4	3.3	3.5	3.5	3.5	3.8
Percentage of Assets	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.9	0.9	0.9	0.9
Percentage of Assets msex:SecuredDebt2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt3

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	3.127	3.197	3.267	3.337	3.407	3.477	3.547	3.617	3.687	3.757	3.827	3.897	3.967	4.037	4.107	4.177	4.247	4.317	4.387	4.457	4.527	4.597	4.667	4.737	4.807	4.877	4.947	5.017	5.227
Percentage of LongTermDebt	1.3	1.3	1.4	1.4	2.0	2.1	2.2	2.4	2.4	2.5	2.6	2.7	2.7	2.8	2.9	3.0	3.1	3.1	3.1	3.2	3.2	3.2	3.3	3.6	3.5	3.7	3.7	3.7	4.0
Percentage of Assets	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.7	0.8	0.8	0.8	0.9	0.9	0.9	0.9	0.9	0.9
Percentage of Assets msex:SecuredDebt3	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt4

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	3.081	3.168	3.255	3.343	3.43	3.517	3.604	3.691	3.779	3.866	3.953	4.04	4.127	4.215	4.302	4.389	4.476	4.563	4.651	4.738	4.825	4.912	4.999	5.087	5.174	5.261	5.348	5.436	5.697
Percentage of LongTermDebt	1.3	1.3	1.4	1.4	2.0	2.1	2.2	2.4	2.5	2.6	2.7	2.8	2.9	2.9	3.0	3.2	3.2	3.3	3.3	3.4	3.4	3.5	3.6	3.8	3.8	4.0	4.0	4.1	4.3
Percentage of Assets	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8	0.8	0.9	0.9	1.0	1.0	1.0	1.0	1.0
Percentage of Assets msex:SecuredDebt4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt5

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	2.396	2.458	2.521	2.583	2.646	2.708	2.771	2.833	2.896	2.959	3.021	3.083	3.146	3.208	3.271	3.333	3.396	3.458	3.521	3.583	3.646	3.708	3.771	3.833	3.896	3.958	4.021	4.083	4.271
Percentage of LongTermDebt	1.0	1.0	1.1	1.1	1.5	1.6	1.7	1.9	1.9	2.0	2.0	2.1	2.2	2.2	2.3	2.4	2.5	2.5	2.5	2.6	2.6	2.6	2.7	2.9	2.9	3.0	3.0	3.1	3.2
Percentage of Assets	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.7	0.8
Percentage of Assets msex:SecuredDebt5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt6

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	4.915	5.043	5.171	5.299	5.427	5.555	5.684	5.812	5.94	6.068	6.197	6.325	6.453	6.581	6.709	6.838	6.966	7.094	7.222	7.35	7.479	7.607	7.735	7.863	7.991	8.12	8.248	8.376	8.761
Percentage of LongTermDebt	2.0	2.1	2.2	2.3	3.1	3.3	3.5	3.8	3.9	4.1	4.2	4.4	4.5	4.6	4.7	4.9	5.0	5.1	5.1	5.3	5.3	5.4	5.5	5.9	5.9	6.1	6.2	6.3	6.7
Percentage of Assets	0.5	0.5	0.6	0.6	0.7	0.7	0.7	0.8	0.8	0.9	0.9	1.0	1.0	1.0	1.1	1.1	1.2	1.2	1.2	1.2	1.3	1.3	1.3	1.4	1.5	1.5	1.6	1.5	1.6
Percentage of Assets msex:SecuredDebt6	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt7

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	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	2015-09-30	2015-06-30	2015-03-31	2014-12-31
Value	8.727	8.837	8.946	9.057	9.167	9.277	9.387	9.497	9.607	9.717	9.827	9.937	10	14	14	14	14	14	12	10	11	8.0
Percentage of LongTermDebt	3.6	3.7	3.8	3.9	5.3	5.5	5.8	6.3	6.4	6.5	6.6	6.9	7.0	9.9	10.3	10.4	10.5	10.5	9.2	7.8	7.7	5.7
Percentage of Assets	0.9	0.9	1.0	1.0	1.1	1.2	1.2	1.3	1.3	1.4	1.5	1.5	1.6	2.3	2.3	2.4	2.5	2.5	2.1	1.9	1.9	1.4
Percentage of Assets msex:SecuredDebt7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebt8

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	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
Value	3.238	3.279	3.32	3.361	3.401	3.442	3.483	3.524	3.566	3.606	3.646	3.687	3.728	3.809
Percentage of LongTermDebt	1.3	1.4	1.4	1.4	2.0	2.0	2.1	2.3	2.4	2.4	2.5	2.6	2.6	2.7
Percentage of Assets	0.3	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6
Percentage of Assets msex:SecuredDebt8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:SecuredDebtZero

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	0.493	0.569	0.643	0.715	0.786	0.856	0.924	0.99	1.055	1.118	1.18	1.241	1.3	1.358	1.415	1.47	1.525	1.578	1.629
Percentage of LongTermDebt	0.2	0.2	0.3	0.3	0.5	0.5	0.6	0.7	0.7	0.8	0.8	0.9	0.9	0.9	1.0	1.1	1.1	1.1	1.2
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3
Percentage of Assets msex:SecuredDebtZero	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustBond

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.06	0.06	0.06	0.06	0.111	0.111	0.111	0.111	0.162	0.162	0.162	0.162	0.213	0.213	0.213	0.213	0.247	0.247	0.254	0.254	0.299	0.299	0.299	0.299	0.344	0.343	0.343	0.344	0.388
Percentage of LongTermDebt	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3
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	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustBond	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustBond1

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.048	0.048	0.05	0.05	0.085	0.085	0.088	0.088	0.124	0.124	0.128	0.128	0.162	0.162	0.166	0.166	0.198	0.198	0.203	0.203	0.236	0.236	0.241	0.241	0.275	0.275	0.281	0.281	0.32
Percentage of LongTermDebt	0.0	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2
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	0.0	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustBond1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.147	0.175	0.175	0.202	0.202	0.228	0.228	0.254	0.253	0.279	0.279	0.304	0.304	0.329	0.329	0.353	0.353	0.376	0.376	0.399	0.399	0.421	0.421	0.443	0.443	0.465	0.465	0.486	0.506
Percentage of LongTermDebt	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.3	0.4	0.4
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	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustNote	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote1

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1.288	1.405	1.405	1.519	1.519	1.632	1.632	1.743	1.743	1.851	1.851	1.958	1.958	2.063	2.062	2.165	2.166	2.267	2.267	2.366	2.366	2.464	2.463	2.559	2.559	2.654	2.654	3.287	3.413
Percentage of LongTermDebt	0.5	0.6	0.6	0.7	0.9	1.0	1.0	1.2	1.2	1.2	1.3	1.4	1.4	1.4	1.4	1.6	1.6	1.6	1.6	1.7	1.7	1.7	1.8	1.9	1.9	2.0	2.0	2.5	2.6
Percentage of Assets	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.6	0.6
Percentage of Assets msex:StateRevolvingTrustNote1	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote10

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2018-12-31	2017-12-31	2016-12-31
Value	0.987	0.987	1.013	1.013	1.064	1.115	1.115
Percentage of LongTermDebt	0.4	0.4	0.4	0.4	0.7	0.8	0.8
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.2	0.2
Percentage of Assets msex:StateRevolvingTrustNote10	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote11

Period End	2020-06-30	2020-03-31	2019-12-31
Value	1.579	1.539	1.309
Percentage of LongTermDebt	0.7	0.6	0.6
Percentage of Assets	0.2	0.2	0.1
Percentage of Assets msex:StateRevolvingTrustNote11	0.0	0.0	0.0

msex:StateRevolvingTrustNote2

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.328	0.328	0.349	0.349	0.369	0.369	0.389	0.389	0.408	0.408	0.427	0.427	0.446	0.446	0.465	0.465	0.483	0.483	0.501	0.501	0.518	0.518	0.536	0.536	0.553	0.553	0.569	0.569	0.602
Percentage of LongTermDebt	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.5
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustNote2	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote3

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.419	0.447	0.446	0.474	0.474	0.501	0.501	0.527	0.527	0.553	0.553	0.578	0.578	0.603	0.603	0.627	0.627	0.651	0.651	0.674	0.674	0.697	0.697	0.72	0.742	0.742	0.742	0.763	0.784
Percentage of LongTermDebt	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.6	0.6	0.6	0.6
Percentage of Assets	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustNote3	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote4

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.214	0.214	0.214	0.225	0.225	0.235	0.235	0.246	0.246	0.256	0.256	0.266	0.266	0.275	0.276	0.285	0.285	0.294	0.294	0.304	0.304	0.313	0.313	0.322	0.322	0.33	0.33	0.339	0.347
Percentage of LongTermDebt	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3
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	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustNote4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote5

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.069	0.069	0.069	0.073	0.073	0.077	0.077	0.08	0.08	0.084	0.084	0.087	0.087	0.091	0.091	0.094	0.094	0.097	0.097	0.101	0.101	0.104	0.104	0.107	0.107	0.11	0.11	0.113	0.116
Percentage of LongTermDebt	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
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	0.0	0.0	0.0	0.0	0.0	0.0
Percentage of Assets msex:StateRevolvingTrustNote5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote6

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.822	0.822	0.851	0.851	0.88	0.879	0.907	0.907	0.935	0.935	0.962	0.962	0.989	0.989	1.015	1.015	1.04	1.04	1.066	1.066	1.09	1.09	1.115	1.115	1.115	0.677	0.467	0.41	0.397
Percentage of LongTermDebt	0.3	0.3	0.4	0.4	0.5	0.5	0.6	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.7	0.7	0.8	0.7	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.5	0.4	0.3	0.3
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustNote6	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote7

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1.829	1.829	1.829	1.892	1.892	1.954	1.954	2.015	2.015	2.075	2.075	2.134	2.133	2.191	2.191	2.248	2.248	2.303	2.303	2.357	2.357	2.411	2.411	2.463	2.463	2.515	2.515	2.565	2.615
Percentage of LongTermDebt	0.8	0.8	0.8	0.8	1.1	1.2	1.2	1.3	1.3	1.4	1.4	1.5	1.5	1.5	1.5	1.6	1.6	1.7	1.6	1.7	1.7	1.7	1.7	1.9	1.8	1.9	1.9	1.9	2.0
Percentage of Assets	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.5	0.5	0.5	0.5	0.5
Percentage of Assets msex:StateRevolvingTrustNote7	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote8

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	0.919	0.955	0.955	0.99	0.99	1.024	1.024	1.057	1.057	1.09	1.09	1.123	1.123	1.154	1.154	1.186	1.185	1.216	1.216	1.246	1.246	1.276	1.276	1.304	1.304	1.333	1.333	1.361	1.388
Percentage of LongTermDebt	0.4	0.4	0.4	0.4	0.6	0.6	0.6	0.7	0.7	0.7	0.7	0.8	0.8	0.8	0.8	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	1.0	1.0	1.0	1.0	1.0	1.1
Percentage of Assets	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.2	0.2
Percentage of Assets msex:StateRevolvingTrustNote8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

msex:StateRevolvingTrustNote9

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2012-12-31
Value	0.288	0.288	0.309	0.309	0.33	0.33	0.351	0.351	0.372	0.372	0.392	0.392	0.411	0.411	0.431	0.431	0.45	0.45	0.469	0.469	0.487	0.488	0.506	0.506	0.524	0.524	0.541	0.576
Percentage of LongTermDebt	0.1	0.1	0.1	0.1	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.4
Percentage of Assets	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1	0.1
Percentage of Assets msex:StateRevolvingTrustNote9	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	237	234	230	228	163	158	152	141	142	140	139	135	136	136	134	130	130	131	136	135	136	137	136	129	132	129	129	130	133	130	131	132	135	131	132	132	134	133
Percentage of LongTermDebtNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	25.0	25.1	25.4	25.7	20.3	20.2	19.9	18.7	19.5	19.9	21.0	20.8	21.4	21.7	21.7	21.4	21.8	22.4	23.3	22.4	23.2	23.8	23.6	23.8	24.6	24.3	24.5	23.6	24.2	23.9	23.4	24.2	24.8	24.6	24.6	26.2	26.8	27.4

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	33	34	34	27	29	29	30	33	35	36	36	33	34	35	36	34	35	36	36	43	44	45	45	18	20	20	21	42	44	43	54	48	51	50	51	26	28	28
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	3.5	3.7	3.8	3.1	3.6	3.8	4.0	4.5	4.8	5.1	5.5	5.1	5.4	5.7	5.8	5.6	5.9	6.2	6.2	7.2	7.5	7.9	7.8	3.4	3.7	3.9	4.0	7.6	8.0	8.0	9.7	8.9	9.4	9.4	9.5	5.1	5.7	5.8

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	2480000.0	2500000.0	2546000.0	2567000.0	2612000.0	2530000.0	2730000.0	1199000.0	1250000.0	1250000.0	1315000.0	1348000.0	1378000.0	1410000.0	1443000.0	1487000.0	2094000.0	2006000.0	1597000.0	1638000.0	1659000.0	1234000.0	1277000.0	1322000.0	1337000.0	1347000.0	1348000.0	1348000.0	991000.0	972000.0	973000.0	977000.0	974000.0	997000.0	995000.0	617000.0	182000.0	154000.0
Percentage of OtherLiabilitiesNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	0.3	0.3	0.3	0.3	0.3	0.3	0.4	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3	0.3	0.3	0.3	0.3	0.2	0.2	0.2	0.2	0.3	0.3	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.1	0.0	0.0

Common Stock Value

us-gaap:CommonStockValue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	216	215	215	170	165	160	157	156	156	155	155	154	154	153	153	152	152	151	150	150	149	149	148	148	147	146	146	145	144	144	143	143	142	142	141	141	140	139
Percentage of CommonStockValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of Assets	22.8	23.1	23.6	19.2	20.4	20.5	20.5	20.8	21.4	22.1	23.5	23.7	24.1	24.5	24.7	24.9	25.3	25.8	25.8	24.9	25.5	25.7	25.8	27.3	27.4	27.6	27.6	26.3	26.2	26.4	25.6	26.1	26.2	26.5	26.3	27.8	28.0	28.5

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	117	111	108	105	98	94	91	88	79	74	74	72	68	66	65	65	60	57	55	54	51	49	48	47	44	42	42	42	39	38	38	38	35	34	35	36	34	33
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	12.3	12.0	11.9	11.9	12.2	12.0	11.9	11.7	10.9	10.6	11.2	11.1	10.7	10.6	10.5	10.7	10.0	9.8	9.6	9.1	8.7	8.5	8.4	8.8	8.2	8.0	8.0	7.7	7.2	7.0	6.8	7.0	6.5	6.4	6.6	7.2	6.8	6.9

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.681	16	12	11	3.956	7.664	13	13	10	8.981	14	8.478	10	10	16	5.941	10	8.39	5.369	8.666	7.147	5.765	4.987	4.026	8.058	9.822	3.961
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	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	13.3	50.9	38.9	31.1	11.9	25.0	39.1	35.3	29.4	28.8	45.2	23.5	30.6	33.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-20270000.0	-25147000.0	-27905000.0	-25522000.0	-23374000.0	-12324000.0	-22576000.0	-21141000.0	-18366000.0	-10011000.0	-16152000.0	-14005000.0	-11588000.0	-9577000.0	-13229000.0	-8699000.0	-5158000.0	-2635000.0	-4027000.0	-9961000.0	-5691000.0	-4923000.0	-5249000.0	-5858000.0	-4036000.0	-9676000.0	-6086000.0
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	-57.5	-79.2	-85.3	-67.6	-70.1	-40.2	-67.9	-54.7	-52.6	-32.1	-51.4	-38.7	-35.1	-31.8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.42	15	4.621	66	16	5.787	9.701	7.206	11	-2.595	4.194	4.539	-0.397	1.201	-0.756	1.242	-3.614	-4.528	-2.271	3.168	-3.708	-1.87	0.113	2.319	-2.679	-0.783	1.177
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	12.5	49.8	14.1	176.8	50.3	18.9	29.2	18.6	32.1	-8.3	13.3	12.6	-1.2	4.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect

Period End	2020-06-30	2020-03-31	2019-06-30	2019-03-31
Value	-11.169	6.802	-2.628	1.127
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	-31.7	21.4	-7.9	3.7

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.681	16	12	11	3.956	7.664	13	13	10	8.981	14	8.478	10	10	16	5.941	10	8.39	5.369	8.666	7.147	5.765	4.987	4.026	8.058	9.822	3.961
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	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	13.3	50.9	38.9	31.1	11.9	25.0	39.1	35.3	29.4	28.8	45.2	23.5	30.6	33.5	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Net Income Loss

us-gaap:NetIncomeLoss

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31
Value	9.713	7.668	8.071	11	8.146	6.552	6.993	12	8.675	4.494	5.345	7.642	5.381	4.441	3.22	8.813	5.919	4.79	4.56	6.743	5.089	3.636	3.79	6.758	4.728	3.169	3.168	5.807	4.481	3.177	2.726	6.138	3.725	1.807
Percentage of NetIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	27.6	24.2	24.7	29.5	24.4	21.4	21.0	31.8	24.9	14.4	17.0	21.1	16.3	14.8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	9.192	7.181	7.902	10	7.423	5.868	6.501	11	8.151	3.983	5.106	7.232	4.972	4.139	4.127	8.154	5.583	4.492	4.236	6.466	4.809	3.377	3.496	6.458	4.416	2.881	2.856	5.505	4.235	2.91	2.43	5.926
Percentage of NetIncomeLoss	94.6	93.6	97.9	93.6	91.1	89.6	93.0	95.8	94.0	88.6	95.5	94.6	92.4	93.2	128.2	92.5	94.3	93.8	92.9	95.9	94.5	92.9	92.2	95.6	93.4	90.9	90.2	94.8	94.5	91.6	89.1	96.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	26.1	22.6	24.2	27.6	22.3	19.1	19.6	30.4	23.4	12.8	16.3	20.0	15.1	13.8	0.0	0.0	0.0	0.0	0.0	0.0	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 RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RegulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:UnregulatedOperation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	0.521	0.487	0.168	0.71	0.723	0.684	0.492	0.52	0.524	0.511	0.24	0.41	0.409	0.302	-0.907	0.659	0.336	0.298	0.325	0.277	0.28	0.259	0.295	0.3	0.312	0.288	0.312	0.302	0.246	0.267	0.296	0.212
Percentage of NetIncomeLoss	5.4	6.4	2.1	6.4	8.9	10.4	7.0	4.2	6.0	11.4	4.5	5.4	7.6	6.8	-28.2	7.5	5.7	6.2	7.1	4.1	5.5	7.1	7.8	4.4	6.6	9.1	9.8	5.2	5.5	8.4	10.9	3.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	1.5	1.5	0.5	1.9	2.2	2.2	1.5	1.3	1.5	1.6	0.8	1.1	1.2	1.0	0.0	0.0	0.0	0.0	0.0	0.0	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 RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:UnregulatedOperation	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	2020-06-30	2020-03-31	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	9.713	7.668	8.07	11	8.146	6.552	6.993	12	8.675	4.494
Percentage of NetIncomeLoss	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	27.6	24.2	24.7	29.5	24.4	21.4	21.0	31.8	24.9	14.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:RetainedEarnings	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	5.196	5.108	4.374	4.403	4.265	4.19	4.037	3.95	4.022	3.771	4.169	3.79	3.476	3.411	3.48	3.252	3.444	3.356	3.097	3.31	3.424	3.256	3.1	3.053	3.028	3.01	3.025	3.128	2.839	2.866	2.883	2.86	2.869	2.62	3.182	2.421	2.417	2.584	3.131	2.387	2.236
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Increase Decrease In Other Operating Capital Net

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-653000.0	-1187000.0	106000.0	939000.0	-2075000.0	164000.0	-690000.0	-498000.0	-1105000.0	-296000.0	-605000.0	64000.0	723000.0	-13000.0	-1320000.0	-1115000.0	818000.0	281000.0	871000.0	-418000.0	-507000.0	200000.0	-864000.0	810000.0	-694000.0	886000.0	-1116000.0	298000.0	-603000.0	589000.0	-449000.0	617000.0	1201000.0	-334000.0	381000.0	245000.0	453000.0	-540000.0	1825000.0	-96000.0
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Increase Decrease In Accounts Receivable

us-gaap:IncreaseDecreaseInAccountsReceivable

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	1796000.0	-1085000.0	-1499000.0	1651000.0	1774000.0	-1780000.0	-1782000.0	2533000.0	1041000.0	-815000.0	-945000.0	1777000.0	1107000.0	-1283000.0	-3144000.0	2365000.0	1378000.0	-530000.0	-2698000.0	2330000.0	-202000.0	618000.0	-1263000.0	109000.0	-9000.0	-787000.0	-1066000.0	1148000.0	-59000.0	-1224000.0	-921000.0	2681000.0	-5196000.0	995000.0	550000.0	-2405000.0	-96000.0	1923000.0	1281000.0	-3037000.0
Percentage of IncreaseDecreaseInAccountsReceivable	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Deferred Income Tax Expense Benefit

us-gaap:DeferredIncomeTaxExpenseBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-3.776	-3.43	-3.34	-3.304	-2.756	-2.319	-2.749	-3.215	-2.877	0.117	-0.45	3.999	3.378	1.017	-1.829	2.061	2.006	1.315	-1.878	16	0.512	0.581	1.023	0.772	0.678	0.657	0.379	1.461	0.364	0.711	0.608	2.361	0.476	0.514	0.801	0.875	0.214	0.208	0.516	-0.465
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Share Based Compensation

us-gaap:ShareBasedCompensation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	470000.0	162000.0	228000.0	-294000.0	474000.0	229000.0	327000.0	222000.0	362000.0	173000.0	167000.0	236000.0	277000.0	160000.0	180000.0	181000.0	327000.0	141000.0	165000.0	131000.0	221000.0	116000.0	109000.0	131000.0	202000.0	97000.0	136000.0	88000.0	192000.0	77000.0	97000.0	84000.0	198000.0	174000.0	79000.0	81000.0	152000.0	82000.0	46000.0	84000.0
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-20270000.0	-25147000.0	-27905000.0	-25522000.0	-23374000.0	-12324000.0	-22576000.0	-21141000.0	-18366000.0	-10011000.0	-16152000.0	-14005000.0	-11588000.0	-9577000.0	-13229000.0	-8699000.0	-5158000.0	-2635000.0	-4027000.0	-9961000.0	-5691000.0	-4923000.0	-5249000.0	-5858000.0	-4036000.0	-9676000.0	-6086000.0
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	-57.5	-79.2	-85.3	-67.6	-70.1	-40.2	-67.9	-54.7	-52.6	-32.1	-51.4	-38.7	-35.1	-31.8	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31
Value	20	25	25	23	12	21	18	10	14	1.588	9.577	14	13	6.672	6.651	7.761	4.885	7.278	4.339	4.165
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

us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperation

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31
Value	19	24	25	23	12	21	18	9.978	13	11	9.572	14	13	6.66	6.613	7.734	4.885	7.211	4.339	4.134
Percentage of PaymentsToAcquirePropertyPlantAndEquipment	98.2	99.3	99.7	99.5	99.7	100.0	99.9	99.7	100.0	729.7	99.9	99.8	98.9	99.8	99.4	99.7	100.0	99.1	100.0	99.3

us-gaap:UnregulatedOperation

Period End	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	2015-09-30	2015-06-30	2014-09-30	2014-06-30	2014-03-31
Value	0.357	0.179	0.085	0.106	0.031	0.0	0.016	0.033	0.007	0.0	0.005	0.024	0.149	0.012	0.038	0.027	0.067	0.0	0.031
Percentage of PaymentsToAcquirePropertyPlantAndEquipment	1.8	0.7	0.3	0.5	0.3	0.0	0.1	0.3	0.0	0.0	0.1	0.2	1.1	0.2	0.6	0.3	0.9	0.0	0.7

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.42	15	4.621	66	16	5.787	9.701	7.206	11	-2.595	4.194	4.539	-0.397	1.201	-0.756	1.242	-3.614	-4.528	-2.271	3.168	-3.708	-1.87	0.113	2.319	-2.679	-0.783	1.177
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax	12.5	49.8	14.1	176.8	50.3	18.9	29.2	18.6	32.1	-8.3	13.3	12.6	-1.2	4.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Proceeds From Issuance Of Long Term Debt

us-gaap:ProceedsFromIssuanceOfLongTermDebt

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.323	5.398	-3.479	69	6.318	6.899	12	3.698	3.274	2.293	4.555	2.921	1.309	2.738	4.682	3.042	2.0	2.0	0.0	3.0	7.848	0.0	4.187	0.211	0.058	0.0	3.976	0.011	55	0.0	4.353	0.576	0.7	0.432	2.308	0.007	3.97	0.0
Percentage of ProceedsFromIssuanceOfLongTermDebt	100.0	100.0	100.0	100.0	100.0	100.0	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	0.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	0.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0

dei:LegalEntity

msex:FirstMortgageBonds

Period End	2020-03-31	2019-12-31
Value	23	9.7
Percentage of ProceedsFromIssuanceOfLongTermDebt	433.5	-278.8

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	0.958	1.33	1.028	3.959	1.019	1.337	1.011	3.869	1.003	1.141	0.996	3.048	0.989	1.126	0.981	2.781	1.044	1.092	0.926	2.623	1.689	1.046	0.803	2.952	0.797	0.929	0.79	2.716	0.837	6.887	52	2.601	0.746	0.844	0.609	5.252	-2.262	0.828	0.594	5.205
Percentage of RepaymentsOfLongTermDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 LongTermDebtAndCapitalLeaseObligations	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Payments Of Dividends Common Stock

us-gaap:PaymentsOfDividendsCommonStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.474	4.468	4.272	3.987	3.963	3.943	3.937	3.668	3.666	3.659	3.658	3.451	3.45	3.443	3.442	3.241	3.228	3.226	3.222	3.119	3.107	3.105	3.101	3.059	3.037	3.034	3.041	2.972	2.967	2.963	2.959	2.911	2.907	2.902	2.899	14	-8.53	2.842	2.838	12
Percentage of PaymentsOfDividendsCommonStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	0.958	1.33	1.028	3.959	1.019	1.337	1.011	3.869	1.003	1.141	0.996	3.048	0.989	1.126	0.981	2.781	1.044	1.092	0.926	2.623	1.689	1.046	0.803	2.952	0.797	0.929	0.79	2.716	0.837	6.887	52	2.601	0.746	0.844	0.609	5.252	-2.262	0.828	0.594	5.205
Percentage of RepaymentsOfLongTermDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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 LongTermDebtAndCapitalLeaseObligations	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

Period End	2020-06-30	2020-03-31	2019-12-31	2019-06-30	2019-03-31	2018-12-31	2017-12-31	2016-12-31	2015-12-31
Value	42	53	46	4.16	6.788	5.661	6.397	4.318	3.908
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Proceeds From Repayments Of Short Term Debt

us-gaap:ProceedsFromRepaymentsOfShortTermDebt

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	4.0	13	-38.5	-0.9	9.9	1.0	0.0	9.5	11	-0.5	3.5	7.5	2.5	2.5	-1.6	3.1	8.5	-1.0	-15.0	0.0	3.0	-4.0	-11.5	2.5	0.5	-0.95	-2.0	-0.5	0.2	2.5	2.0	-1.0	0.0	4.0	2.45	0.8	-1.8	5.3
Percentage of ProceedsFromRepaymentsOfShortTermDebt	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	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	100.0

msex:ChangeInUnbilledRevenues

Period End	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31
Value	2237000.0	-481000.0	1172000.0	1305000.0	-353000.0	353000.0	1752000.0	-7000.0
Percentage of ChangeInUnbilledRevenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:CommercialOperatingRevenues

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	3.649	3.369	3.659	4.487	3.744	3.309	3.546	4.418	3.771	3.109	3.435	4.074	3.493	2.954
Percentage of CommercialOperatingRevenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:CostOfTreatedWater

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	932000.0	793000.0	785000.0	818000.0	827000.0	770000.0	773000.0	836000.0	703000.0	888000.0	935000.0	791000.0	795000.0	779000.0	840000.0	804000.0	754000.0	801000.0	229000.0	775000.0	766000.0	730000.0	56000.0	764000.0	802000.0	778000.0	97000.0	780000.0	762000.0	761000.0	134000.0	772000.0	775000.0
Percentage of CostOfTreatedWater	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:CostOfUntreatedWater

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	782000.0	870000.0	879000.0	878000.0	782000.0	861000.0	872000.0	948000.0	850000.0	930000.0	895000.0	673000.0	573000.0	659000.0	689000.0	675000.0	570000.0	666000.0	1231000.0	674000.0	552000.0	642000.0	1337000.0	642000.0	515000.0	606000.0	1461000.0	618000.0	515000.0	606000.0	1309000.0	663000.0	516000.0
Percentage of CostOfUntreatedWater	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:IndustrialOperatingRevenues

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	2.175	2.081	2.148	2.723	2.321	2.198	2.314	2.868	2.689	2.312	2.156	2.587	2.395	2.183
Percentage of IndustrialOperatingRevenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:InterSegmentEliminationOperatingRevenues

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	-192000.0	-129000.0	-142000.0	-251000.0	-138000.0	-125000.0	-123000.0	-219000.0	-131000.0	-129000.0	-132000.0	-220000.0	-127000.0	-112000.0
Percentage of InterSegmentEliminationOperatingRevenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:NonregualtedContractOperationsRevenue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	3.076	2.859	3.044	2.919	2.986	2.824	4.391	4.203	3.781	3.999	4.056	4.041	3.762	3.649
Percentage of NonregualtedContractOperationsRevenue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:OperationsAndMaintenance

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30
Value	17	17	17	17	16	16	18	18	16	17	16	16	16	15	17	16	15	15	16	16	16	16	14	14	14	15	15	15	15	15	15	15	14
Percentage of OperationsAndMaintenance	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:OtherNonregulatedRevenues

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	104000.0	103000.0	101000.0	101000.0	100000.0	102000.0	101000.0	101000.0	101000.0	101000.0	102000.0	90000.0	111000.0	101000.0
Percentage of OtherNonregulatedRevenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:ResidentialCommercialIndustrialAndFireProtectionRevenue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	3.06	3.045	3.08	3.1	3.098	3.013	3.054	3.084	3.073	2.888	2.978	3.01	2.911	2.913
Percentage of ResidentialCommercialIndustrialAndFireProtectionRevenue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:ResidentialOperatingRevenues

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	19	16	17	20	17	15	16	19	17	15	15	18	17	15
Percentage of ResidentialOperatingRevenues	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:WholesaleMunicipalRevenue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	3.827	3.698	3.737	3.813	3.429	3.339	3.444	4.319	3.68	3.212	3.288	3.634	3.397	3.234
Percentage of WholesaleMunicipalRevenue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:AllowanceForFundsUsedDuringConstructionInvestingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	306000.0	429000.0	449000.0	317000.0	215000.0	168000.0	176000.0	142000.0	73000.0	52000.0	71000.0	56000.0	56000.0	38000.0	70000.0	64000.0	41000.0	21000.0	34000.0	46000.0	40000.0	32000.0	35000.0	26000.0	25000.0	24000.0	32000.0	36000.0	31000.0	14000.0	34000.0
Percentage of AllowanceForFundsUsedDuringConstructionInvestingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:CommonStockDividendsPerShareCashPaid

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	0.2563	0.2563	0.2563	0.24	0.24	0.24	0.24	0.2238	0.2238	0.2238	0.2238	0.2113	0.2113	0.2113	0.2117	0.1988	0.1988	0.1988	0.1985	0.1925	0.1925	0.1925	0.193	0.19	0.19	0.19	0.1905	0.1875	0.1875	0.1875	0.188	0.185	0.185	0.185	0.1855	0.1825	0.1825	0.1825	0.183	0.18	0.18
Percentage of CommonStockDividendsPerShareCashPaid	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ContributionOfProperty

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	2374000.0	1422000.0	2395000.0	1550000.0	2220000.0	1605000.0	807000.0	964000.0	1780000.0	284000.0	540000.0	2107000.0	472000.0	659000.0	222000.0	-178000.0	504000.0	891000.0	819000.0	408000.0	448000.0	766000.0	4801000.0	667000.0	1086000.0	44000.0	1852000.0	1033000.0	-106000.0	397000.0	187000.0
Percentage of ContributionOfProperty	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementClassOfStock

us-gaap:ConvertiblePreferredDividendsNetOfTax

us-gaap:ConvertiblePreferredStock

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-09-30
Value	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	17000.0	24000.0	24000.0	25000.0	24000.0	24000.0
Percentage of ConvertiblePreferredDividendsNetOfTax	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:CostOfPurchasedWater

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	1714000.0	1663000.0	1664000.0	1696000.0	1609000.0	1631000.0	1645000.0	1784000.0	1553000.0	1818000.0	1830000.0	1464000.0	1368000.0	1438000.0	1529000.0	1479000.0	1324000.0	1467000.0	1460000.0	1449000.0	1318000.0	1372000.0	1393000.0	1406000.0	1317000.0	1384000.0	1558000.0	1398000.0	1277000.0	1367000.0	1443000.0	1435000.0	1291000.0	1331000.0	1332000.0	1354000.0	1168000.0
Percentage of CostOfPurchasedWater	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:OtherPensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	-338000.0	-338000.0	-330000.0	-330000.0	-330000.0	-330000.0	-447000.0	-447000.0	-447000.0	-447000.0	-445000.0	-445000.0	-445000.0	-445000.0	-443000.0	-443000.0	-443000.0	-443000.0
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

us-gaap:PensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	-515000.0	-515000.0	-405000.0	-404000.0	-404000.0	-404000.0	-414000.0	-415000.0	-415000.0	-415000.0	-392000.0	-391000.0	-391000.0	-391000.0	-356000.0	-357000.0	-357000.0	-357000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses	152.4	152.4	122.7	122.4	122.4	122.4	92.6	92.8	92.8	92.8	88.1	87.9	87.9	87.9	80.4	80.6	80.6	80.6

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:OtherPensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	721000.0	721000.0	613000.0	613000.0	613000.0	613000.0	638000.0	637000.0	637000.0	637000.0	602000.0	601000.0	601000.0	601000.0	539000.0	558000.0	558000.0	558000.0
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

us-gaap:PensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	1409000.0	1409000.0	1174000.0	1173000.0	1173000.0	1173000.0	1218000.0	1218000.0	1218000.0	1218000.0	1122000.0	1122000.0	1122000.0	1122000.0	1003000.0	1004000.0	1004000.0	1004000.0
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets	195.4	195.4	191.5	191.4	191.4	191.4	190.9	191.2	191.2	191.2	186.4	186.7	186.7	186.7	186.1	179.9	179.9	179.9

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:OtherPensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	425000.0	425000.0	496000.0	496000.0	496000.0	496000.0	475000.0	474000.0	474000.0	474000.0	491000.0	491000.0	491000.0	491000.0	488000.0	488000.0	488000.0	488000.0
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

us-gaap:PensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	775000.0	775000.0	856000.0	857000.0	857000.0	857000.0	765000.0	765000.0	765000.0	765000.0	786000.0	786000.0	786000.0	786000.0	762000.0	761000.0	761000.0	761000.0
Percentage of DefinedBenefitPlanInterestCost	182.4	182.4	172.6	172.8	172.8	172.8	161.1	161.4	161.4	161.4	160.1	160.1	160.1	160.1	156.1	155.9	155.9	155.9

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:OtherPensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	290000.0	290000.0	422000.0	423000.0	423000.0	423000.0	166000.0	166000.0	166000.0	166000.0	174000.0	175000.0	175000.0	175000.0	235000.0	216000.0	216000.0	216000.0
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

us-gaap:PensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	490000.0	490000.0	630000.0	631000.0	631000.0	631000.0	567000.0	569000.0	569000.0	569000.0	656000.0	655000.0	655000.0	655000.0	692000.0	691000.0	691000.0	691000.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost	169.0	169.0	149.3	149.2	149.2	149.2	341.6	342.8	342.8	342.8	377.0	374.3	374.3	374.3	294.5	319.9	319.9	319.9

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:OtherPensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	248000.0	248000.0	209000.0	210000.0	210000.0	210000.0	284000.0	284000.0	284000.0	284000.0	272000.0	272000.0	272000.0	272000.0	275000.0	275000.0	275000.0	275000.0
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

us-gaap:PensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	609000.0	609000.0	543000.0	543000.0	543000.0	543000.0	606000.0	607000.0	607000.0	607000.0	600000.0	600000.0	600000.0	600000.0	577000.0	577000.0	577000.0	577000.0
Percentage of DefinedBenefitPlanServiceCost	245.6	245.6	259.8	258.6	258.6	258.6	213.4	213.7	213.7	213.7	220.6	220.6	220.6	220.6	209.8	209.8	209.8	209.8

us-gaap:Depreciation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	4.629	4.448	4.301	4.246	4.123	4.046	3.9	3.792	3.736	3.609	3.642	3.587	3.385	3.308
Percentage of Depreciation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsCommonStockCash

Period End	2020-06-30	2020-03-31	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	4.475	4.468	4.272	3.987	3.964	3.943	3.937	3.667	3.666	3.659
Percentage of DividendsCommonStockCash	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	2020-06-30	2020-03-31	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	4.475	4.468	4.272	3.987	3.964	3.943	3.937	3.667	3.666	3.659
Percentage of DividendsCommonStockCash	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DividendsPreferredStockCash

Period End	2020-06-30	2020-03-31	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	30000.0	30000.0	30000.0	30000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0
Percentage of DividendsPreferredStockCash	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	2020-06-30	2020-03-31	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	30000.0	30000.0	30000.0	30000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0
Percentage of DividendsPreferredStockCash	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInAccountsPayable

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-1313000.0	810000.0	3128000.0	2122000.0	4080000.0	-5349000.0	-210000.0	3122000.0	5399000.0	-2915000.0	1816000.0	-2932000.0	6058000.0	-3356000.0	2012000.0	742000.0	3089000.0	-25000.0	-2084000.0	-316000.0	1971000.0	600000.0	-841000.0	520000.0	1080000.0	-733000.0	1954000.0	-759000.0	607000.0	718000.0	-434000.0	-555000.0	-29000.0	-880000.0	-83000.0	85000.0	534000.0	-1233000.0	887000.0	293000.0
Percentage of IncreaseDecreaseInAccountsPayable	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInAccruedTaxesPayable

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31
Value	-1059000.0	3530000.0	-4497000.0	-258000.0	-5076000.0	3236000.0	-588000.0	118000.0	97000.0	3185000.0	-463000.0	-1256000.0	-2973000.0	3725000.0	1753000.0	1193000.0	-3438000.0	3751000.0	-2211000.0	-1163000.0	-41000.0	3593000.0	-1615000.0	611000.0	-1301000.0	3121000.0	-1092000.0	-572000.0	-1439000.0	1969000.0	26000.0	-12000.0	-892000.0	2297000.0	-2824000.0	1434000.0	-1926000.0	2411000.0	-872000.0
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	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInDeferredRevenue

Period End	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31
Value	119000.0	-1000.0	1000.0	22000.0	-11000.0	62000.0	8000.0	15000.0	-11000.0	-5000.0	43000.0	1000.0	19000.0	5000.0	9000.0	10000.0	8000.0	11000.0	10000.0	12000.0	-13000.0	74000.0	-3000.0	-56000.0	82000.0	-4000.0	7000.0	-4000.0	3000.0	10000.0	59000.0	-50000.0	-17000.0	-115000.0	-28000.0	30000.0	-56000.0
Percentage of IncreaseDecreaseInDeferredRevenue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInInterestPayableNet

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	1230000.0	-1169000.0	1232000.0	-480000.0	692000.0	-702000.0	741000.0	-711000.0	757000.0	-591000.0	702000.0	-687000.0	667000.0	-673000.0	683000.0	-690000.0	673000.0	-686000.0	693000.0	-707000.0	664000.0	-680000.0	703000.0	-719000.0	699000.0	-700000.0	709000.0	-702000.0	-125000.0	314000.0	-366000.0	-301000.0	716000.0	-722000.0	733000.0	-785000.0	842000.0	-760000.0	771000.0	-780000.0
Percentage of IncreaseDecreaseInInterestPayableNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	390000.0	450000.0	-472000.0	2164000.0	-2830000.0	26000.0	-688000.0	1052000.0	-1890000.0	-588000.0	-558000.0	-722000.0	-702000.0	62000.0	-432000.0	-589000.0	-599000.0	19000.0	2993000.0	-3273000.0	-849000.0	1000000.0	-523000.0	-1488000.0	-737000.0	-495000.0	-107000.0	-1800000.0	861000.0	-94000.0	88000.0	-1664000.0	1746000.0	100000.0	-365000.0	-2117000.0	737000.0	154000.0	-1724000.0	-430000.0
Percentage of IncreaseDecreaseInPensionAndPostretirementObligations	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInPrepaidExpense

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	2171000.0	-577000.0	-1210000.0	-340000.0	1654000.0	-381000.0	-875000.0	-286000.0	1753000.0	-356000.0	-180000.0	-324000.0	1361000.0	-473000.0	-789000.0	-429000.0	1250000.0	-43000.0	-701000.0	-144000.0	1337000.0	-446000.0	-992000.0	-57000.0	1577000.0	-267000.0	-963000.0	-43000.0	993000.0	-514000.0	-7000.0	20000.0	119000.0	501000.0	501000.0	114000.0	-713000.0	-123000.0	196000.0	-30000.0
Percentage of IncreaseDecreaseInPrepaidExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	-2000.0	-169000.0	286000.0	-216000.0	-104000.0	68000.0	-222000.0	807000.0	671000.0	37000.0	-323000.0	-440000.0	240000.0	547000.0	-305000.0	-333000.0	1837000.0	295000.0	-81000.0	358000.0	107000.0	-37000.0	115000.0	-220000.0	215000.0	159000.0	-4000.0	-116000.0	128000.0	573000.0	-49000.0	-589000.0	-2000.0	20000.0	-14000.0	-60000.0	-426000.0	673000.0	-272000.0	-129000.0
Percentage of IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementClassOfStock

us-gaap:IncrementalCommonSharesAttributableToConversionOfPreferredStock

us-gaap:ConvertiblePreferredStock

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31	2012-09-30
Value	115000.0	115000.0	115000.0	115000.0	115000.0	115000.0	115000.0	115000.0	115000.0	115000.0	115.0	115000.0	115000.0	115.0	115000.0	115000.0	115000.0	115000.0	140000.0	163.0	167.0	166830.0	167.0	167.0
Percentage of IncrementalCommonSharesAttributableToConversionOfPreferredStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestPaidCapitalized

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	306000.0	429000.0	449000.0	317000.0	215000.0	168000.0	176000.0	142000.0	73000.0	52000.0	71000.0	56000.0	56000.0	38000.0	70000.0	64000.0	41000.0	21000.0	34000.0	46000.0	40000.0	32000.0	35000.0	26000.0	25000.0	24000.0	32000.0	126000.0	-31000.0	-14000.0	-316000.0	244000.0	-49000.0	-54000.0	-78000.0	-352000.0	193000.0	-62000.0	-62000.0	-543000.0
Percentage of InterestPaidCapitalized	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestPaidNet

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31
Value	732000.0	3022000.0	1009000.0	2528000.0	1104000.0	2297000.0	1023000.0	2379000.0	878000.0	1833000.0	841000.0	2181000.0	805000.0	1789000.0	772000.0	2120000.0	764000.0	1774000.0	805000.0	2214000.0	836000.0	1847000.0	774000.0	2201000.0	840000.0	1930000.0	868000.0	2248000.0	1695000.0	932000.0	2261000.0	2068000.0	1021000.0	2187000.0	971000.0	2447000.0	830000.0	2088000.0	988000.0
Percentage of InterestPaidNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LeaseAndRentalExpense

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	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	200000.0	200000.0	200000.0	200000.0	100000.0	100000.0	200000.0	200000.0	100000.0	100000.0	0	0
Percentage of LeaseAndRentalExpense	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0

us-gaap:LifeInsuranceCorporateOrBankOwnedChangeInValue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31
Value	252000.0	-205000.0	65000.0	-13000.0	77000.0	123000.0	-146000.0	59000.0	58000.0	2000.0	48000.0	47000.0	62000.0	52000.0	12000.0	45000.0	25000.0	-45000.0	48000.0	48000.0	27000.0	11000.0	49000.0	21000.0	52000.0	62000.0	53000.0	59000.0	19000.0	42000.0	158000.0	-68000.0	-50000.0	-128000.0	131000.0	-45000.0	-55000.0
Percentage of LifeInsuranceCorporateOrBankOwnedChangeInValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LineOfCreditFacilityInterestRateDuringPeriod

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30
Value	0.0165	0.0258	-0.0012	0.0326	0.0352	0.0364	0.0008	0.0324	0.031	0.0274	0.0008	0.0228	0.0208	0.0178	0.0002	0.0154	0.0152	0.0141	0.0001	0.0119	0.0118	0.0117	-0.0003	0.0144	0.0142	0.0145	0.0006	0.0132	0.0134	0.014	0.0002	0.0152	0.0138	0.0131	-0.0006	0.0132	0.0159
Percentage of LineOfCreditFacilityInterestRateDuringPeriod	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod

Period End	2020-06-30	2020-03-31	2019-06-30	2019-03-31
Value	36	21	50	50
Percentage of LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod	100.0	100.0	100.0	100.0

us-gaap:PurchaseCommitmentExcludingLongtermCommitment

us-gaap:LongTermPurchaseCommitmentMinimumQuantityRequired

msex:PurchaseCommitment1

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30
Value	0.0	3.0	0.0	0.0	0.0	3.0	-2.997	0.0	0.0	3.0	-2.997	0.0	0.0	0.0	3.0	2.999997	0.0
Percentage of LongTermPurchaseCommitmentMinimumQuantityRequired	0.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0	0.0	100.0	100.0	0.0	0.0	0.0	100.0	100.0	0.0

msex:PurchaseCommitment2

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31
Value	0.0	15	0.0	0.0	0.0	15	-14.985	0.0	0.0	15	-14.985	0.0	0.0	0.0	15
Percentage of LongTermPurchaseCommitmentMinimumQuantityRequired	0.0	500.0	0.0	0.0	0.0	500.0	500.0	0.0	0.0	500.0	500.0	0.0	0.0	0.0	500.0

us-gaap:PurchaseCommitment

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30
Value	0.0	27	0.0	0.0	0.0	27	-26.973	0.0	0.0	27	-26.973	0.0	0.0	0.0	27	26	0.0
Percentage of LongTermPurchaseCommitmentMinimumQuantityRequired	0.0	900.0	0.0	0.0	0.0	900.0	900.0	0.0	0.0	900.0	900.0	0.0	0.0	0.0	900.0	900.0	0.0

us-gaap:NumberOfReportableSegments

Period End	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31
Value	2.0	2.0	2.0	2.0	2.0	2.0	2.0	0	0	0	2.0
Percentage of NumberOfReportableSegments	100.0	100.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	0.0	100.0

us-gaap:PaymentsOfDebtIssuanceCosts

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	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	2015-09-30	2014-12-31	2014-09-30	2013-12-31	2012-12-31	2012-09-30	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31
Value	9000.0	24000.0	15000.0	753000.0	18000.0	787000.0	55000.0	20000.0	86000.0	111000.0	30000.0	3000.0	-6000.0	143000.0	-1000.0	62000.0	72000.0	61000.0	2000.0	1138000.0	0	3000.0	15000.0	0	19000.0	18000.0
Percentage of PaymentsOfDebtIssuanceCosts	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	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	0.0	100.0	100.0

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	30000.0	30000.0	30000.0	30000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	36000.0	43000.0	43000.0	44000.0	51000.0	52000.0	51000.0
Percentage of PaymentsOfDividendsPreferredStockAndPreferenceStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PaymentsOfStockIssuanceCosts

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2015-12-31	2010-12-31	2010-09-30
Value	0	37000.0	335000.0	17000.0	-1000.0	6000.0	0	0	244000.0
Percentage of PaymentsOfStockIssuanceCosts	0.0	100.0	100.0	100.0	100.0	100.0	0.0	0.0	100.0

us-gaap:RetirementPlanType

us-gaap:PensionAndOtherPostretirementBenefitContributions

us-gaap:OtherPensionPlansDefinedBenefit

Period End	2020-06-30	2020-03-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	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
Value	300000.0	300000.0	200000.0	200000.0	200000.0	900000.0	200000.0	200000.0	200000.0	900000.0	200000.0	200000.0	200000.0	200000.0	500000.0	200000.0
Percentage of PensionAndOtherPostretirementBenefitContributions	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ProceedsFromIssuanceOfCommonStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30
Value	0.295	0.313	44	5.368	4.522	2.559	0.286	0.268	0.31	0.286	0.326	0.316	0.291	0.301	0.294	0.329	0.397	0.433	0.347	0.381	0.362	0.372	0.373	0.401	0.334	0.385	0.111	0.374	0.476	0.407	0.394	0.405	0.386	0.402	0.336	0.393	0.389	0.386	0.376	0.367
Percentage of ProceedsFromIssuanceOfCommonStock	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31
Value	1273000.0	2489000.0	862000.0	1761000.0	1068000.0	651000.0	1606000.0	2100000.0	858000.0	182000.0	589000.0	448000.0	8000.0	270000.0	321000.0	74000.0	1177000.0	-565000.0	71000.0	20000.0	73000.0	-335000.0
Percentage of ProceedsFromPaymentsForOtherFinancingActivities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2011-03-31	2010-12-31	2010-09-30	2010-06-30
Value	795000.0	1123000.0	1116000.0	871000.0	643000.0	515000.0	557000.0	424000.0	214000.0	167000.0	229000.0	174000.0	180000.0	119000.0	232000.0	207000.0	119000.0	61000.0	83000.0	113000.0	103000.0	82000.0	104000.0	80000.0	66000.0	67000.0	84000.0	104000.0	89000.0	38000.0	101000.0	110000.0	137000.0	136000.0	195000.0	235000.0	197000.0	194000.0	185000.0	143000.0	348000.0
Percentage of PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	488000.0	694000.0	667000.0	555000.0	428000.0	347000.0	381000.0	282000.0	141000.0	115000.0	158000.0	118000.0	124000.0	81000.0	162000.0	143000.0	78000.0	40000.0	49000.0	66000.0	63000.0	50000.0	69000.0	54000.0	41000.0	43000.0	52000.0	67000.0	58000.0	24000.0	67000.0
Percentage of PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RegulatoryAgency, dei:LegalEntity

us-gaap:PublicUtilitiesApprovedRateIncreaseDecreaseAmount

msex:NewJerseyBoardOfPublicUtilities, msex:Middlesex

Period End	2020-06-30	2020-03-31
Value	0	600000.0
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount	0.0	100.0

msex:PennsylvaniaPublicUtilitiesCommissio, msex:TwinLakes

Period End	2020-06-30	2020-03-31	2019-07-31
Value	0	100000.0	200000.0
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount	0.0	16.7	0.0

us-gaap:RegulatedOperatingRevenueOther

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	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	124000.0	62000.0	78000.0	184000.0	73000.0	58000.0	59000.0	151000.0	63000.0	62000.0	69000.0	162000.0	48000.0	50000.0
Percentage of RegulatedOperatingRevenueOther	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StockIssuedDuringPeriodSharesDividendReinvestmentPlan

Period End	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	2015-09-30	2015-06-30	2015-03-31	2014-09-30	2014-06-30	2014-03-31	2013-09-30	2013-06-30	2013-03-31
Value	0.047649	0.091883	0.082026	0.047649	0.005975	0.007361	0.007665	0.0082	0.008109	0.007845	0.008916	0.010946	0.015488	15	16	16	0.019549	0.016159	0.018919	0.018271	0.024387	0.020991
Percentage of StockIssuedDuringPeriodSharesDividendReinvestmentPlan	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock

Period End	2020-06-30	2020-03-31	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	0.004	0.005	0.004	0.092	0.082	0.048	0.006	0.008	0.007	0.008
Percentage of StockIssuedDuringPeriodSharesDividendReinvestmentPlan	0.0	10.5	0.0	100.1	100.0	100.7	0.0	133.9	95.1	104.4

us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesRestrictedStockAwardGross

us-gaap:CommonStock

Period End	2020-06-30
Value	4000.0
Percentage of StockIssuedDuringPeriodSharesRestrictedStockAwardGross	100.0

us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures

us-gaap:CommonStock

Period End	2020-06-30	2019-12-31	2019-09-30	2019-06-30	2018-12-31	2018-09-30	2018-06-30
Value	17000.0	0	1000.0	17000.0	-1000.0	0	23000.0
Percentage of StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures	100.0	0.0	100.0	100.0	100.0	0.0	100.0

us-gaap:StockIssuedDuringPeriodValueDividendReinvestmentPlan

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31
Value	0.294	0.313	0.289	5.368	4.522	2.559	0.25	0.266	0.31	0.3	0.334	0.3	0.3	0.3	0.253	0.4	0.4	0.4	0.362	0.4	0.3	0.4	0.393	0.4	0.3	0.4	0.353	0.4	0.5	0.4	0.387
Percentage of StockIssuedDuringPeriodValueDividendReinvestmentPlan	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock

Period End	2020-06-30	2020-03-31	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	0.294	0.313	0.289	5.368	4.522	2.559	0.286	0.266	0.31	0.286
Percentage of StockIssuedDuringPeriodValueDividendReinvestmentPlan	100.0	100.0	100.0	100.0	100.0	100.0	114.4	100.0	100.0	95.3

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardGross

Period End	2020-06-30
Value	245000.0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardGross	100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock

Period End	2020-06-30
Value	245000.0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardGross	100.0

us-gaap:StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures

Period End	2020-06-30	2020-03-31	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	226000.0	162000.0	228000.0	172000.0	278000.0	229000.0	347000.0	242000.0	214000.0	174000.0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock

Period End	2020-06-30	2020-03-31	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	226000.0	162000.0	228000.0	172000.0	278000.0	229000.0	347000.0	242000.0	214000.0	174000.0
Percentage of StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StockholdersEquityOther

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	1000.0	37000.0	334000.0	15000.0	-1000.0	6000.0
Percentage of StockholdersEquityOther	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	1000.0	37000.0	334000.0	15000.0	-1000.0	6000.0
Percentage of StockholdersEquityOther	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:TaxesOther

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30
Value	3.643	3.602	3.469	3.871	3.539	3.504	3.418	3.889	3.637	3.384	3.238	3.603	3.415	3.309	3.407	3.796	3.428	3.312	3.296	3.39	3.22	3.061	2.964	3.213	3.043	2.954	2.925	3.123	3.058	3.034	2.994	3.281
Percentage of TaxesOther	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:AccumulatedDeferredIncomeTaxes

Period End	2020-06-30	2020-03-31	2019-12-31
Value	57	55	54
Percentage of AccumulatedDeferredIncomeTaxes	100.0	100.0	100.0

msex:ConstructionAdvances

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2017-12-31
Value	24	24	23	22	23	22	22	21
Percentage of ConstructionAdvances	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

dei:LegalEntity

msex:ConstructionLoanMaximumBorrowingCapacity

msex:FirstMortgageBonds

Period End	2020-03-31	2019-12-31	2019-09-30	2019-08-31
Value	60	60	60	53
Percentage of ConstructionLoanMaximumBorrowingCapacity	100.0	100.0	100.0	100.0

msex:Middlesex

Period End	2020-06-30	2020-03-31	2019-09-30
Value	0.413	37	30
Percentage of ConstructionLoanMaximumBorrowingCapacity	0.0	60.9	49.7

us-gaap:LineOfCreditFacility

msex:DelawareStateRevolvingFund

Period End	2020-03-31	2019-04-30
Value	1.5	1.7
Percentage of ConstructionLoanMaximumBorrowingCapacity	2.5	0.0

us-gaap:LongtermDebtType

msex:FirstMortgageBonds

Period End	2020-06-30	2019-08-31
Value	0.608	0.537
Percentage of ConstructionLoanMaximumBorrowingCapacity	0.0	1.0

msex:DeferredChargesAndOtherAssets

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2013-12-31	2011-06-30	2010-12-31
Value	160	168	175	174	121	124	118	118	118	115	74	76	75	75	75	75	74	74	78	94	83	85	87	58	64	67
Percentage of DeferredChargesAndOtherAssets	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:FairValueByMeasurementBasis

msex:FirstMortgageBondsFairValueDisclosure

us-gaap:CarryingReportedAmountFairValueDisclosure

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2012-12-31
Value	150	150	151	151	100	100	101	101	104	95	95	80	82	82	82	82	84	84	85	85	87	88	88	88	90	87	87	87	89	91
Percentage of FirstMortgageBondsFairValueDisclosure	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:EstimateOfFairValueFairValueDisclosure

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-06-30	2012-12-31
Value	162	160	160	154	103	103	102	101	106	96	98	82	84	84	84	86	88	87	87	87	86	90	90	88	89	81	79	84	93
Percentage of FirstMortgageBondsFairValueDisclosure	107.5	106.4	106.2	102.0	102.7	102.3	101.4	100.3	101.7	101.6	102.8	103.0	102.5	102.5	102.5	104.6	105.4	103.8	103.3	102.2	99.8	102.6	101.7	99.9	98.3	93.7	91.2	94.0	101.8

msex:NonUtilityAssetsNet

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2012-12-31	2011-06-30	2010-12-31
Value	10	10	10	10	10	10	9.989	9.651	9.598	9.567	9.478	9.276	9.252	9.253	9.131	9.41	9.389	9.254	9.199	9.236	9.292	9.264	9.197	9.254	9.259	9.482	9.44	11	11	9.882	7.455	7.122
Percentage of NonUtilityAssetsNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RegulatoryAgency, dei:LegalEntity

msex:OtherLoanSourceMaximumBorrowingCapacity

msex:NewJerseyBoardOfPublicUtilities, msex:Middlesex

Period End	2020-06-30	2020-02-28
Value	1.0	100
Percentage of OtherLoanSourceMaximumBorrowingCapacity	100.0	100.0

msex:PreliminarySurveyAndInvestigationCharges

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	2013-06-30	2012-12-31	2011-06-30	2010-12-31
Value	2670000.0	2208000.0	2054000.0	2252000.0	2116000.0	5359000.0	5254000.0	5049000.0	4859000.0	4647000.0	4676000.0	3832000.0	3142000.0	2876000.0	2365000.0	2690000.0	2424000.0	2278000.0	2199000.0	5024000.0	5117000.0	5687000.0	7023000.0
Percentage of PreliminarySurveyAndInvestigationCharges	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:TaxPeriod

msex:ReserveProvision

us-gaap:TaxYear2014

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31
Value	500000.0	500000.0	500000.0	2400000.0	3100000.0	3100000.0	4100000.0
Percentage of ReserveProvision	100.0	100.0	100.0	100.0	100.0	100.0	100.0

msex:RightOfUseAssetsAccumulatedAmortization

Period End	2020-06-30	2020-03-31	2019-12-31
Value	1700000.0	1500000.0	1400000.0
Percentage of RightOfUseAssetsAccumulatedAmortization	100.0	100.0	100.0

msex:RightOfUseAssetsCurrent

Period End	2020-06-30	2020-03-31	2019-12-31
Value	5600000.0	5800000.0	5900000.0
Percentage of RightOfUseAssetsCurrent	100.0	100.0	100.0

msex:TotalCommonEquity

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2012-12-31	2011-12-31	2011-06-30	2010-12-31
Value	333	327	323	275	263	254	248	245	236	230	229	227	222	219	218	218	212	208	206	204	200	198	197	196	191	189	188	188	184	181	176	174	173
Percentage of TotalCommonEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	216	215	215	170	165	160	157	156	156	155	155	153	150	148	146	143	141	139
Percentage of TotalCommonEquity	64.9	65.9	66.4	61.8	62.7	63.0	63.2	63.9	66.2	67.5	67.7	70.1	72.9	75.4	77.5	79.0	79.9	80.5

us-gaap:RetainedEarnings

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2016-12-31	2015-12-31	2014-12-31	2013-12-31	2012-12-31	2011-12-31	2010-12-31
Value	117	111	108	105	98	94	91	88	79	74	74	65	55	48	42	38	35	33
Percentage of TotalCommonEquity	35.1	34.1	33.6	38.2	37.3	37.0	36.8	36.1	33.8	32.5	32.3	29.9	27.1	24.6	22.5	21.0	20.1	19.5

us-gaap:CapitalizationLongtermDebtAndEquity

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2013-12-31
Value	573	564	556	506	429	414	404	388	380	372	370	365	361	358	355	351	345	342	345	342	339	338	335	321
Percentage of CapitalizationLongtermDebtAndEquity	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:ContributionsInAidOfConstruction

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	104	101	97	95	91	89	87	85	82	80	79	78	76	76	75	74	74	73	73	71	70	69	69	64	63	62	61	61	60	60	59	59	59	58	58	56	56	49
Percentage of ContributionsInAidOfConstruction	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DebtInstrumentUnamortizedDiscount

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	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	4417000.0	4470000.0	4506000.0	4551000.0	3857000.0	3912000.0	3969000.0	4008000.0	3280000.0	3276000.0	3309000.0	3276000.0	3216000.0	3238000.0	3287000.0	3338000.0	3248000.0	3284000.0	3339000.0
Percentage of DebtInstrumentUnamortizedDiscount	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DebtInstrumentUnamortizedPremium

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	7866000.0	7964000.0	8064000.0	8164000.0	1150000.0	1204000.0	1259000.0	1314000.0	1369000.0	1314000.0	1367000.0	1335000.0	1388000.0	1442000.0	1495000.0	1548000.0	1602000.0	1654000.0	1707000.0	1760000.0	1814000.0	1867000.0	1920000.0	1972000.0	1967000.0	2017000.0	2072000.0	2124000.0	2236000.0
Percentage of DebtInstrumentUnamortizedPremium	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:DeferredRevenueCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	1329000.0	1210000.0	1211000.0	1048000.0	1047000.0	1025000.0	1036000.0	1036000.0	974000.0	966000.0	951000.0	962000.0	967000.0	922000.0	923000.0	904000.0	899000.0	890000.0	880000.0	872000.0	861000.0	851000.0	839000.0	852000.0	778000.0	781000.0	837000.0	755000.0	759000.0	752000.0	756000.0	753000.0	743000.0	684000.0	734000.0	751000.0	866000.0	864000.0
Percentage of DeferredRevenueCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:GuarantyLiabilities

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2013-12-31
Value	1300000.0	1400000.0	1400000.0	1400000.0	1500000.0	1500000.0	1500000.0	100000.0	100000.0	100000.0	100000.0	100000.0	100000.0	100000.0	100000.0	100000.0	200000.0	200000.0	200000.0	200000.0	300000.0	300000.0	300000.0	300000.0	300000.0	400000.0
Percentage of GuarantyLiabilities	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:InterestPayableCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	2092000.0	862000.0	2031000.0	799000.0	1279000.0	587000.0	1289000.0	548000.0	1259000.0	502000.0	1093000.0	391000.0	1078000.0	411000.0	1084000.0	401000.0	1091000.0	418000.0	1104000.0	411000.0	1118000.0	454000.0	1134000.0	431000.0	1150000.0	451000.0	1151000.0	442000.0	955000.0
Percentage of InterestPayableCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LiabilitiesOtherThanLongtermDebtNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2013-12-31
Value	188	189	190	181	183	185	182	184	185	187	146	149	145	143	142	142	141	139	137	141	127	127	126	94
Percentage of LiabilitiesOtherThanLongtermDebtNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:LineOfCreditFacilityCurrentBorrowingCapacity

Period End	2020-06-30	2020-03-31
Value	37	33
Percentage of LineOfCreditFacilityCurrentBorrowingCapacity	100.0	100.0

us-gaap:LineOfCreditFacility

msex:BankOfAmerica

Period End	2020-06-30	2020-03-31
Value	1.0	11
Percentage of LineOfCreditFacilityCurrentBorrowingCapacity	2.7	32.8

msex:CoBank

Period End	2020-06-30	2020-03-31
Value	7.5	2.0
Percentage of LineOfCreditFacilityCurrentBorrowingCapacity	20.0	6.0

msex:PncBank

Period End	2020-06-30	2020-03-31
Value	29	20
Percentage of LineOfCreditFacilityCurrentBorrowingCapacity	77.3	61.2

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity

Period End	2020-06-30	2020-03-31
Value	102	106
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	100.0	100.0

us-gaap:LineOfCreditFacility

msex:BankOfAmerica

Period End	2020-06-30	2020-03-31
Value	59	49
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	57.6	46.0

msex:CoBank

Period End	2020-06-30	2020-03-31
Value	4.5	10.0
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	4.4	9.4

msex:PncBank

Period End	2020-06-30	2020-03-31
Value	39	47
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	38.0	44.6

us-gaap:SubsequentEventType

us-gaap:SubsequentEvent

Period End	2020-07-31	2020-04-30
Value	106	106
Percentage of LineOfCreditFacilityRemainingBorrowingCapacity	0.0	0.0

us-gaap:OperatingLeaseLiability

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31
Value	5329000.0	5558000.0	5732000.0	5908000.0	6084000.0	6260000.0
Percentage of OperatingLeaseLiability	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OtherLongTermDebt

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2011-12-31
Value	91	87	83	80	729	67	61	49	46	54	52	64	62	61	59	56	53	53	54	53	52	53	50	43	44	44	45	45	46	47	47	49
Percentage of OtherLongTermDebt	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:OtherLongTermDebtCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2018-12-31
Value	7340000.0	7171000.0	7178000.0	7343000.0
Percentage of OtherLongTermDebtCurrent	100.0	100.0	100.0	100.0

us-gaap:PreferredStockSharesAuthorized

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	120000.0	120000.0	120000.0	123000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126000.0	126.0	126000.0	126000.0	126000.0	126000.0	126000.0	130000.0	130000.0	130000.0	130000.0	130000.0	130000.0
Percentage of PreferredStockSharesAuthorized	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PreferredStockSharesOutstanding

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	20000.0	20000.0	20000.0	20000.0	23000.0	23000.0	23000.0	23000.0	24000.0	24000.0	24000.0	24000.0	24000.0	24000.0	24000.0	24000.0	24000.0	24.0	24000.0	24000.0	24000.0	24000.0	24000.0	24000.0	24000.0	28000.0	28000.0	28000.0	28000.0
Percentage of PreferredStockSharesOutstanding	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementClassOfStock

msex:NonredeemablePreferredStock1

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	4750.0	4750.0	10000.0	10000.0	10.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0
Percentage of PreferredStockSharesOutstanding	50.0	50.0	50.0	50.0	43.5	43.5	43.5	43.5	41.7	41.7	41.7	41.7	41.7	19.8	19.8	41.7	41.7	41.7	41.7	41.7	41.7	41.7	41.7	41.7	41.7	35.7	35.7	35.7	35.7

us-gaap:ConvertiblePreferredStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	7000.0	7000.0	10000.0	10000.0	10.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	10000.0	14000.0	14000.0	14000.0	14000.0
Percentage of PreferredStockSharesOutstanding	50.0	50.0	50.0	50.0	43.5	43.5	43.5	43.5	41.7	41.7	41.7	41.7	41.7	29.2	29.2	41.7	41.7	41.7	41.7	41.7	41.7	41.7	41.7	41.7	41.7	50.0	50.0	50.0	50.0

us-gaap:NonredeemablePreferredStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	7000.0	7000.0	1000.0	1000.0	1.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0	1000.0
Percentage of PreferredStockSharesOutstanding	5.0	5.0	5.0	5.0	4.3	4.3	4.3	4.3	4.2	4.2	4.2	4.2	4.2	29.2	29.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2	4.2	3.6	3.6	3.6	3.6

us-gaap:PreferredStockValue

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	2084000.0	2084000.0	2084000.0	2084000.0	2433000.0	2433000.0	2433000.0	2433000.0	2433000.0	2433000.0	2433000.0	2433000.0	2435000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2436000.0	2435000.0	2859000.0	2886000.0	2886000.0	3353000.0
Percentage of PreferredStockValue	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:StatementClassOfStock

us-gaap:ConvertiblePreferredStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1005000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1007000.0	1006000.0	1429000.0	1457000.0	1457000.0	1457000.0
Percentage of PreferredStockValue	48.2	48.2	48.2	48.2	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.4	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.3	41.3	50.0	50.5	50.5	43.5

us-gaap:NonredeemablePreferredStock

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	79000.0	79000.0	79000.0	79000.0	79000.0	79000.0	79000.0	78000.0	79000.0	78000.0	78000.0	79000.0	79000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0	80000.0
Percentage of PreferredStockValue	3.8	3.8	3.8	3.8	3.2	3.2	3.2	3.2	3.2	3.2	3.2	3.2	3.2	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3	3.3	2.8	2.8	2.8	2.4

us-gaap:PrepaidExpenseCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	3961000.0	1790000.0	2367000.0	3577000.0	3917000.0	2263000.0	2644000.0	3519000.0	3805000.0	2052000.0	2408000.0	2588000.0	2912000.0	1551000.0	2024000.0	2813000.0	3242000.0	1992000.0	2035000.0	2736000.0	2880000.0	1543000.0	1989000.0	2981000.0	3038000.0	1461000.0	1728000.0	2691000.0	2734000.0	1741000.0	2255000.0	2262000.0	2242000.0	1121000.0	1622000.0	2123000.0	2237000.0	1401000.0
Percentage of PrepaidExpenseCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesInventory

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	5274000.0	5276000.0	5445000.0	5159000.0	5375000.0	5479000.0	5411000.0	5633000.0	4826000.0	4155000.0	4118000.0	4441000.0	4881000.0	4641000.0	4094000.0	4399000.0	4732000.0	2895000.0	2600000.0	2681000.0	2323000.0	2216000.0	2253000.0	2138000.0	2358000.0	2143000.0	1984000.0	1988000.0	2104000.0	1976000.0	1403000.0	1452000.0	2041000.0	2003000.0	2023000.0	2009000.0	1949000.0	2196000.0
Percentage of PublicUtilitiesInventory	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	177	173	170	166	163	160	157	154	151	149	146	143	140	138	135	133	131	129	126	124	121	120	117	115	113	111	110	107	104	102	100	98	95	93	92	90	88	84
Percentage of PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	61	48	75	69	56	40	32	37	26	18	11	21	13	14	12	20	14	9.528	5.734	12	9.527	10	8.145	11	6.774	6.201	8.41	10	12	11	7.834	12	9.94	14	12	16	14	11
Percentage of PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	161	161	160	157	157	156	156	155	154	154	153	149	149	147	146	146	144	143	142	140	140	138	138	136	135	133	132	131	130	130	129	129	129	128	127	125	124	118
Percentage of PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentNet

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	746	726	705	677	654	628	618	599	580	564	557	545	533	524	517	506	497	486	481	477	473	468	465	456	451	447	446	442	440	437	435	433	429	425	422	417	412	398
Percentage of PublicUtilitiesPropertyPlantAndEquipmentNet	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	82	82	83	80	78	77	74	71	70	69	69	67	67	66	63	62	62	61	61	60	59	58	58	57	57	56	55	55	55	54	54	53	54	48	47	45	44	44
Percentage of PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentPlantInService

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	923	900	875	844	818	789	775	753	732	713	703	688	673	662	653	640	628	615	608	601	595	588	583	572	564	559	556	550	545	540	535	531	525	519	514	507	500	483
Percentage of PublicUtilitiesPropertyPlantAndEquipmentPlantInService	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentTransmissionAndDistribution

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	617	607	556	536	525	515	512	489	480	471	468	449	443	435	430	411	407	401	398	388	386	380	378	366	364	362	359	352	346	343	343	334	332	329	326	320	317	308
Percentage of PublicUtilitiesPropertyPlantAndEquipmentTransmissionAndDistribution	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RegulatoryAssetsNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	111	110	110	100	99	98	99	101	99	99	58	60	60	60	60	57	58	58	58	65	64	65	66	34	34	34	34	58	59	60	72	65	66	66	67	37	37	38
Percentage of RegulatoryAssetsNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RegulatoryLiabilityNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	64	67	69	72	73	76	79	81	83	84	43	11	11	11	11	11	11	11	10	10	10	10	10	10	9.828	9.613	9.639	9.449	8.811
Percentage of RegulatoryLiabilityNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:RestrictedCashAndCashEquivalentsNoncurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2013-06-30	2013-03-31	2012-12-31	2012-09-30	2012-06-30	2012-03-31	2011-12-31	2011-09-30	2011-06-30	2010-12-31
Value	28	37	44	53	1.17	1.802	1.956	1.956	3.157	0.778	1.46	0.439	0.439	0.439	0.439	0.439	0.439	0.439	0.439	0.439	0.455	1.596	2.573	3.438	4.937	1.886	2.473	3.091	5.362	2.634	9.019	4.053	5.838	2.518	3.26	4.552	5.911	7.056
Percentage of RestrictedCashAndCashEquivalentsNoncurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

us-gaap:UnbilledReceivablesCurrent

Period End	2020-06-30	2020-03-31	2019-12-31	2019-09-30	2019-06-30	2019-03-31	2018-12-31	2018-09-30	2018-06-30	2018-03-31	2017-12-31	2017-09-30	2017-06-30	2017-03-31	2016-12-31	2016-09-30	2016-06-30	2016-03-31	2015-12-31	2015-09-30	2015-06-30	2015-03-31	2014-12-31	2014-09-30	2014-06-30	2014-03-31	2013-12-31	2013-09-30	2012-12-31
Value	8939000.0	6702000.0	7183000.0	9417000.0	8245000.0	6940000.0	7293000.0	9097000.0	8744000.0	6992000.0	6999000.0	8628000.0	8284000.0	6378000.0	6590000.0	8531000.0	8154000.0	6539000.0	6246000.0	7991000.0	7592000.0	6187000.0	5937000.0	7427000.0	7054000.0	5306000.0	5652000.0	6993000.0	5483000.0
Percentage of UnbilledReceivablesCurrent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

Line plots across dimensions of each concept

us-gaap:RegulatedAndUnregulatedOperatingRevenue
us-gaap:StatementBusinessSegments
(None,)

us-gaap:OperatingIncomeLoss
us-gaap:StatementBusinessSegments
(None,)

us-gaap:NetIncomeLoss
us-gaap:StatementBusinessSegments
(None,)

Operating Margin
us-gaap:StatementBusinessSegments
(None,)

us-gaap:Assets
us-gaap:StatementBusinessSegments
(None,)

us-gaap:LongTermDebt
us-gaap:DebtInstrument
(None,)

us-gaap:NetIncomeLoss
us-gaap:StatementBusinessSegments
(None,)

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment
us-gaap:StatementBusinessSegments
(None,)