NI


Line plots across dimensions of each concept
Tables

Table of contents



us-gaap:CommonStockValue

us-gaap:CommonStockParOrStatedValuePerShare

us-gaap:SharesIssued
us-gaap:StatementEquityComponents

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesAuthorized

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax
us-gaap:MajorCustomers
us-gaap:MajorCustomers, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments

us-gaap:Revenues
us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments, us-gaap:Subsegments

us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization

us-gaap:OperatingCostsAndExpenses

us-gaap:OperatingIncomeLoss
us-gaap:StatementBusinessSegments

us-gaap:InterestExpense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic

us-gaap:NonoperatingIncomeExpense

us-gaap:IncomeTaxExpenseBenefit

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:Assets

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:AssetsCurrent

us-gaap:CashAndCashEquivalentsAtCarryingValue

us-gaap:AccountsReceivableNetCurrent

us-gaap:InventoryRawMaterialsAndSupplies

us-gaap:OtherAssetsCurrent

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures

us-gaap:Goodwill
us-gaap:StatementBusinessSegments

us-gaap:OtherAssetsNoncurrent

us-gaap:LiabilitiesCurrent

us-gaap:AccountsPayableCurrent

us-gaap:TaxesPayableCurrent

us-gaap:OtherLiabilitiesCurrent

us-gaap:DividendsPayableCurrent

us-gaap:LiabilitiesNoncurrent

us-gaap:OtherLiabilitiesNoncurrent

us-gaap:StockholdersEquity
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:TreasuryStockValue

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:ProfitLoss
us-gaap:StatementEquityComponents

us-gaap:DepreciationDepletionAndAmortization

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:EffectiveIncomeTaxRateContinuingOperations

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents
dei:LegalEntity
nix:BusinessesImpactedbyIncident

nix:CashFromFinancingActivitiesRelatedToChangeInShortTermBorrowingsDueToSecuritizationTransactions

nix:CostsResultingfromtheGreaterLawrenceIncident

nix:ExpensesOtherThanThirdPartyClaims

nix:ExpensesRelatedtoThirdPartyClaims
dei:LegalEntity
nix:GasMetersAffected

nix:GreaterLawrenceIncidentImpactonOperationandMaintenanceExpense

nix:ImpairmentAndGainLossOnSaleOfAssetsNet

nix:IncreaseDecreaseInDeferredChargesAndOtherNonCurrentAssets

nix:MiscellaneousNonOperatingIncomeExpense
us-gaap:Range, dei:LegalEntity
nix:PenaltyPerViolationofEmergencyResponsePlan
us-gaap:Range, dei:LegalEntity
nix:PenaltyforViolationsofEmergencyResponsePlan

nix:PensionandOtherPostretirementNonServiceCost

nix:SecuritizationTransactionFees

nix:ServiceAreaByCounty

us-gaap:CapitalExpendituresIncurredButNotYetPaid

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect
us-gaap:SubsequentEventType
us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:DeferredIncomeTaxesAndTaxCredits
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanContributionsByEmployer
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:DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss

us-gaap:DividendsCommonStockCash
us-gaap:StatementEquityComponents

us-gaap:DividendsPreferredStockCash
us-gaap:StatementEquityComponents

us-gaap:FinancingReceivableAllowanceForCreditLossesRecovery
us-gaap:StatementBusinessSegments

us-gaap:FinancingReceivableAllowanceForCreditLossesWriteOffs
us-gaap:StatementBusinessSegments

us-gaap:GainLossOnSaleOfBusiness

us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:IncreaseDecreaseInAssetRetirementObligations

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities

us-gaap:IncreaseDecreaseInRegulatoryAssetsAndLiabilities

us-gaap:IncrementalCommonSharesAttributableToContingentlyIssuableShares

us-gaap:IncrementalCommonSharesAttributableToEquityForwardAgreements

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InsuranceRecoveries

us-gaap:InterestIncomeExpenseNonoperatingNet

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax

us-gaap:OtherOperatingActivitiesCashFlowStatement

us-gaap:PaymentsForProceedsFromOtherInvestingActivities

us-gaap:PaymentsForRemovalCosts

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt
us-gaap:StatementClassOfStock
us-gaap:PreferredStockAmountOfPreferredDividendsInArrears

us-gaap:PreferredStockDividendsIncomeStatementImpact
us-gaap:StatementClassOfStock
us-gaap:PreferredStockDividendsPerShareDeclared
us-gaap:StatementClassOfStock
us-gaap:PreferredStockPerShareAmountsOfPreferredDividendsInArrears

us-gaap:ProceedsFromIssuanceOfCommonStock

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities

us-gaap:ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesDebt

us-gaap:ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths

us-gaap:ProvisionForLoanLeaseAndOtherLosses
us-gaap:StatementBusinessSegments

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest
us-gaap:PublicUtilitiesRegulatoryProceeding, dei:LegalEntity
us-gaap:PublicUtilitiesApprovedRateIncreaseDecreaseAmount
us-gaap:PublicUtilitiesRegulatoryProceeding, us-gaap:SubsequentEventType, dei:LegalEntity
us-gaap:SubsequentEventType, dei:LegalEntity
us-gaap:PublicUtilitiesRequestedRateIncreaseDecreaseAmount

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents

us-gaap:RegulatedOperatingRevenue
us-gaap:StatementBusinessSegments

us-gaap:RegulatedOperatingRevenueOther
us-gaap:StatementBusinessSegments

us-gaap:RepaymentsOfLongTermDebtAndCapitalSecurities

us-gaap:RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths

us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueEmployeeStockPurchasePlan
us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation
us-gaap:StatementEquityComponents

us-gaap:TaxesExcludingIncomeAndExciseTaxes

us-gaap:UtilitiesOperatingExpenseMaintenanceAndOperations

nix:AccruedInsuranceClaimsCurrent

nix:CommonDividendsPayableCurrent

nix:CustomerAccountsReceivableBilledLessReserve

nix:CustomerAccountsReceivableUnbilledLessReserve

nix:DeferredChargesAndOther

nix:ExchangeGasPayable

nix:ExchangeGasReceivable

nix:LegalAndEnvironmentalReserves
us-gaap:LossContingenciesByNatureOfContingency
nix:LiabilityForEstimatedRemediationCosts

nix:PreferredDividendsPayableCurrent

nix:PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyAtCostLessAccumulatedDepreciation

nix:PublicUtilitiesPropertyPlantAndEquipmentPlantInServiceNet
us-gaap:PublicUtilitiesRegulatoryProceeding, dei:LegalEntity
nix:RegulatoryNetCapitalExpendituresIncludedInFiling
us-gaap:PublicUtilitiesRegulatoryProceeding, us-gaap:SubsequentEventType, dei:LegalEntity

nix:TradeReceivablesAvailableForTransfer

nix:TradeReceivablesNotTransferred

nix:TradeReceivablesTransferredNet

us-gaap:AccountsReceivableGrossCurrent

us-gaap:AccrualForEnvironmentalLossContingencies

us-gaap:AccruedInsuranceNoncurrent

us-gaap:AccumulatedDeferredInvestmentTaxCredit

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent

us-gaap:AssetRetirementObligationsNoncurrent

us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap:FinancialInstrument
us-gaap:DerivativeInstrumentRisk
us-gaap:AvailableForSaleSecurities
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue

us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:FinancialInstrument

us-gaap:AvailableForSaleSecuritiesDebtSecuritiesNoncurrent

us-gaap:CapitalizationLongtermDebtAndEquity

us-gaap:CommercialPaper

us-gaap:ContractWithCustomerLiabilityCurrent

us-gaap:DebtInstrumentCarryingAmount

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLoss

us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPosition

us-gaap:DeferredIncomeTaxLiabilitiesNet
us-gaap:BalanceSheetLocation
us-gaap:DerivativeAssets
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:DerivativeInstrumentsAndHedgesLiabilitiesNoncurrent
us-gaap:BalanceSheetLocation
us-gaap:DerivativeLiabilities
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:EmployeeRelatedLiabilitiesCurrent

us-gaap:EnergyRelatedInventoryCoal

us-gaap:EnergyRelatedInventoryNaturalGasInStorage

us-gaap:FinancialLiabilitiesFairValueDisclosure
us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FinancingReceivableAllowanceForCreditLosses
us-gaap:StatementBusinessSegments

us-gaap:InterestPayableCurrent

us-gaap:InvestmentsAndOtherNoncurrentAssets

us-gaap:LIFOInventoryAmount

us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent
us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:ShortTermDebtType
us-gaap:LineOfCredit
us-gaap:ShortTermDebtType
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

us-gaap:LongTermDebtAndCapitalLeaseObligations

us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent

us-gaap:LongTermDebtFairValue

us-gaap:OtherLongTermInvestments
us-gaap:Range, us-gaap:ShortTermDebtType
us-gaap:OtherShortTermBorrowings
us-gaap:ShortTermDebtType

us-gaap:PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent
us-gaap:StatementClassOfStock
us-gaap:PreferredStockLiquidationPreference
us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType

us-gaap:PreferredStockParOrStatedValuePerShare

us-gaap:PreferredStockSharesOutstanding

us-gaap:PreferredStockValueOutstanding

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentNet

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentPlantInService

us-gaap:RegulatoryAssetsCurrent

us-gaap:RegulatoryAssetsNoncurrent

us-gaap:RegulatoryLiabilityCurrent

us-gaap:RegulatoryLiabilityNoncurrent

us-gaap:RestrictedCashAndCashEquivalents

us-gaap:ShortTermBorrowings
us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtWeightedAverageInterestRate

us-gaap:TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount

Tables

  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:CommonStockValue █████████████████████████████▁333333333333333333333333333332
us-gaap:CommonStockParOrStatedValuePerShare ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█▁0.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.10.01
us-gaap:SharesIssued ██▇▇▇▇▆▆▃▃▃▁▁▁382382373373373372363362337337336325324323NANANA319NANANA316NANANANANANANANA
 us-gaap:SharesIssued us-gaap:StatementEquityComponents us-gaap:CommonStock██▇▇▇▇▆▆▃▃▃▁▁▁386386377377376376367366341340340329328326NANANA322NANANA318NANANANANANANANA
 us-gaap:SharesIssued us-gaap:StatementEquityComponents us-gaap:PreferredStock██████▇▇▁▁440000.0440000.0440000.0440000.0440000.0420000.0400000.0400000.00.00.0NANANA0.0NANANA0.0NANANANANANANANANANANANA
us-gaap:CommonStockSharesOutstanding ██▇▇▇▇▇▇▅▅▅▄▄▄▄▄▄▄▃▃▃▃▃▃▃▃▃▃▃▁382382373373373372363362337337336325324323322322321319318317317316315315314313312311309284
us-gaap:CommonStockSharesAuthorized ████▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁600600600600400400400400400400400400400400400400400400400400400400400400400400400400400400
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding 384NA374375374NA363355338NA332325325NA323322322NA321317317NA316316315313313312300295
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic 383NA374373373NA363354338NA331325323NA322321320NA318317316NA315315314312312311290284
us-gaap:EarningsPerShareBasic ▅▃▅█▇▄▁▅█▄▅▄▇▆▅▅▇▅▅▄█▇▅▆█▅▆█▅▆0.16-0.41-0.020.760.55-0.05-0.950.070.82-0.160.04-0.140.650.280.080.090.560.19-0.02-0.110.850.490.10.250.850.160.230.840.060.25
us-gaap:EarningsPerShareDiluted ▅▃▅█▇▄▁▅█▄▅▄▇▆▅▅▇▅▅▄█▇▅▆█▅▆█▅▆0.16-0.41-0.020.750.55-0.05-0.950.070.81-0.160.04-0.140.650.270.080.090.560.19-0.02-0.110.850.490.10.250.850.160.230.830.060.23
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax ▄▄▁▂▆▄▁▂▅▃▁▂▅▃▁▁▄▂▁▃▇▅▂▃█▂▃▅▂▂15251358891969183414368559821717134488399015981197861897143610978171169214916911123133523201076121217829561038
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers nix:Commercial▆▅▁▁█▅▁▂▇389344227236449354221243425NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers nix:Industrial▁▃▂▄█▄▂▃▇183201196208246212192199237NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers nix:Residential▆▅▁▂█▅▁▂▇91577843748010948224115021008NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments nix:Commercial,nix:GasDistributionOperations▆▅▁▂█▅▁▂▇2692289012133023580127308NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments nix:Misc.,us-gaap:CorporateAndOther█████▁███200000.0200000.0200000.0200000.0200000.0100000.0200000.0200000.0200000.0NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments nix:Residential,nix:GasDistributionOperations▆▅▁▂█▅▁▂▇796670288375975709257389893NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments nix:ElectricOperations▁▂▇▃▅▃█▃▄354366439383408381449386401NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments nix:GasDistributionOperations▆▅▁▂█▅▁▂▇1171992451585142610544065951315NANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments us-gaap:CorporateAndOther█████▁███200000.0200000.0200000.0200000.0200000.0100000.0200000.0200000.0200000.0NANANANANANANANANANANANANANANANANANANANANA
us-gaap:Revenues ▅▃▂▂▆▃▁▂▅▄▁▂▅▃▁▁▄▂▁▃▇▅▂▃█▂▃▅▂▂1605124193110101869133889510071750136891799015981297861897143610978171169214916911123133523201076121217829561038
 us-gaap:Revenues us-gaap:StatementBusinessSegments nix:ElectricOperations▁▂▇▃▄▃▇▃▄▄█377393467406431403476405423420486NANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:StatementBusinessSegments nix:GasDistributionOperations▇▅▁▂█▅▁▂▇▅▁12311006466607144210614216051330951434NANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:StatementBusinessSegments,us-gaap:Subsegments nix:ElectricOperations,nix:Unaffiliated377NA467406430NA476404423NA485NANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:StatementBusinessSegments,us-gaap:Subsegments nix:GasDistributionOperations,nix:Unaffiliated1228NA4636031438NA4186011327NA431NANANANANANANANANANANANANANANANANANANA
 us-gaap:Revenues us-gaap:StatementBusinessSegments,us-gaap:Subsegments us-gaap:CorporateAndOther,nix:Unaffiliated200000.0NA200000.0200000.0200000.0NA200000.0200000.0200000.0NA100000.0NANANANANANANANANANANANANANANANANANANA
us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization 462NANANA680NANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OperatingCostsAndExpenses 1457NANANA1495NANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OperatingIncomeLoss ▅▃▄▇▇▃▁▅▇▆▄▅▇▅▅▅▇▅▄▅█▆▅▅█▅▅▇▅▅148-3891463374-78-31511840027099124416224113138381219109165530351157219533176193428137208
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments nix:ElectricOperations▁▁▂▁▁█▂▁▁▁▂78851408595386134828379125NANANANANANANANANANANANANANANANANANANA
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments nix:GasDistributionOperations▅▅▄█▇▃▁▅█▆▅7869-48379275-254-45539321183-15NANANANANANANANANANANANANANANANANANANA
us-gaap:InterestExpense ▃▃▃▃▃▂▁▂▃▃▂▂▁▂▁▂▂▃▃█▇█▆▆▆▅▅▄▆▅9293959495888388939287878588858690949411711111510910910910310298107103
us-gaap:OtherNonoperatingIncomeExpense ▄▂▃▃▃▃▃▅█▁▄▃▃▃▃▂▃▄▄▄▄▃▄▄▄▄▅▄▃▃5-51001-11231-1243133-6055671974413422
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic ▅▃▄█▇▃▁▅▇▆▅▄▇▆▅▅▇▆▅▄█▆▅▅█▅▅▇▅▅60-136-3369277-165-4343033816516-70332140324629113120-42426236571184297710433331108
us-gaap:NonoperatingIncomeExpense ▇▆▆▆▆▇▅▇█▆▇▂▇▇▇▇▇▇▇▁▆▅▆▆▆▆▇▆▆▆-87-98-94-94-96-87-118-88-61-105-83-195-84-84-81-92-89-88-89-207-103-114-100-101-104-99-88-94-105-100
us-gaap:IncomeTaxExpenseBenefit ▄▄▄▅▅▁▂▄▅█▄▃▆▅▄▄▆▅▄▄▇▅▄▅▇▄▄▆▄▅-142-107259-153-945622172-2612151817111665-1515082253916227321181137
us-gaap:ProfitLoss ▆▃▅█▇▅▁▅█▄▅▄▇▆▅▅▇▅▅▄█▆▅▆█75-1396296218-11-33924276-5214-4421188272817959-4-272751543178266NANANANANA
 us-gaap:ProfitLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings▆▃▅█▇▅▁▅75-1396296218-11-33924NANANANANANANANANANANA-36268NANANANANANANANANA
us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest ▄▃▄█▇▄▁▅█▄▅▄▇▇▅▄▆▅▄▄█▆▅▅█-62-101-42268203-51-31622310-525-602162424-2311143-4-252771453179267NANANANANA
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic ▆▃▅█▇▅▁▅█▄▅▄61-153-7283205-19-34523276-5214-44NANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:Assets ▆▆▅▅▅▅▄▄▃▃▃▂▂▂▂▁▁▁▁█▇▇▆▆▆▅▅▅▄▄225922265922132219742188921804206992030720098199611926918822186351869118067176171747117492170552560624898248662371023257231072208421621216362083820409
us-gaap:LiabilitiesAndStockholdersEquity ▆▆▅▅▅▅▄▄▃▃▃▂▂▂▂▁▁▁▁█▇▇▆▆▆▅▅▅▄▄225922265922132219742188921804206992030720098199611926918822186351869118067176171747117492170552560624898248662371023257231072208421621216362083820409
us-gaap:StockholdersEquity ▆▇▆▇▆▆▄▅▃▂▂▂▂▂▁▁▁▁▁██▇▇▇▇▆▆▆▅▄574159865848597657795750507354634506432043634122419140713811381038723843380065056523617560076028601257005702569054105105
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital██▇▇▇▇▆▆▃▃▃▁▁▁66716666642664176406640361616151554055295518522551745153NANANA5078NANANA4787476447344715NANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:PreferredStock██████▄▄▁▁88088088088088088039339400NANANA0NANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:AssetsCurrent █▃▁▂▃▄▁▁▂▃▁▁▂▃▁▁▁▂▂▅▅▅▄▄▅▃▃▄▃▃322518531378157819152055136913151633176313321280147117621378125913951577163723352261246620112054232017451707203118381751
us-gaap:CashAndCashEquivalentsAtCarryingValue ▄▃▁▁▃▂▁▂▁▁▁▁▁▁▁▁▁▁▁█▁▁▁▁▁▁▁▂▁▂203139282315111241683529191728261615231531496422517183814441011252
us-gaap:AccountsReceivableNetCurrent ▃▄▂▄▇▆▁▂▅▅▁▂▄▄▁▁▃▃▁▃▇▆▂▄█▂▃▆▁▂716856539870113210585005849738984805458138474714746476605006721152107063982412715917161070526553
us-gaap:InventoryRawMaterialsAndSupplies █▆▆▅▄▄▃▃▄▄▄▃▃▄▃▄▃▁▁▅▅▄▄▄▄▃▆▅▃▃13012011511110710197991041051029697101100102948684112109106106106104991141119999
us-gaap:OtherAssetsCurrent ▄▃▂▂▃▃▂▂▃▃▁▂▃▃▁▂▃▂▁▃▄▄▂██▆▅▅▇▇18214985103144129891091551326591139130648913310775133187169103320321246224228280274
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁█████▇▆▅▅▄▄1122222455566666666452447452443437407327279260215211
us-gaap:Goodwill ▁▁▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂███████████148514851690169016901690169016901690169016901690169016901690169016901690169036663666366636663666366636663666366636773677
 us-gaap:Goodwill us-gaap:StatementBusinessSegments nix:GasDistributionOperations▁▁█████1485148516901690169016901690NANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAssetsNoncurrent ▁▁▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▇▇▇▆▆▆▇████356836634053404440224000393839403801362936813671367536613627360436073609352457095697571954565475551958965971603460456140
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:LiabilitiesCurrent █▇▅▇██▅▃▅▅▃▃▆▆▄▃▂▃▁▃▃▇▄▆▅▄▁▄▃▃416137453339381340154036341125603226317825662778366434522911269624952657207325242758395430483431334030052068297427272662
us-gaap:AccountsPayableCurrent ▄▅▃▄▆█▃▃▃▅▃▃▃▄▂▂▂▃▂▃▄▅▃▃▆▂▂▄▁▁505666494552675883433455497625447451461539352371392433349429563670427459714369393527300292
us-gaap:TaxesPayableCurrent ▅▆▂▃▆▅▂▃▅▄▂▂▅▄▁▁▄▃▁▅█▇▄▅█▃▄▇▃▃223231157167232222150165212208148152216195130140203183137221287266189216278181202258172185
us-gaap:OtherLiabilitiesCurrent ▃▃▂▂▁▁▁▁▂▂▂▁▁▂▁▁▂▂▂▆▆▇█▇▆▆▆▅▅▄1801441208679585475109901197876826768103114121313317378408347323308283269232219
us-gaap:DividendsPayableCurrent 99NA948294NA82706505857560535349049NA8208282787878747468
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:LiabilitiesNoncurrent ▁▂▂▂▂▁▂▂▂▁▁▂▂▂▃▃▂▂▂██▇▆▆▆▆▆▆▅▅487150715090507449854910512051925079495148215144519051105247525351975043504867456712658062566157611562886234616758815834
us-gaap:OtherLiabilitiesNoncurrent ▂▃▄▄▃▁▃▁▂▂▂▂▂▂▁▂▂▃▂▆███▄▃▃▃▄▅▅187218224222218177215184191194187188199200182187188208186270294291297224219219216225246242
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:StockholdersEquity ▆▇▆▇▆▆▄▅▃▂▂▂▂▂▁▁▁▁▁██▇▇▇▇▆▆▆▅▄574159865848597657795750507354634506432043634122419140713811381038723843380065056523617560076028601257005702569054105105
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital██▇▇▇▇▆▆▃▃▃▁▁▁66716666642664176406640361616151554055295518522551745153NANANA5078NANANA4787476447344715NANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:PreferredStock██████▄▄▁▁88088088088088088039339400NANANA0NANANANANANANANANANANANANANANANA
us-gaap:CommonStockValue █████████████████████████████▁333333333333333333333333333332
us-gaap:RetainedEarningsAccumulatedDeficit ▁▁▂▂▁▁▁▂▂▂▂▂▂▂▂▂▂▂▂███▇██▇▇▇▆▇-1483-1370-1231-1144-1358-1399-1387-965-919-1073-1020-975-874-972-1060-1067-1042-1123-1182156115971494133913901394113311641170925980
us-gaap:TreasuryStockValue ██████████▇▇▇▇▇▇▆▆▆▆▆▃▃▃▃▂▂▂▁▁999999999999999999959494938887878679797979585858584848484040
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▁▅▄▆▆▇█▇▇▇▇▇▇▇▃▃▅▇▇▇▇▆▇▇▇▆▆▆▆▆-230-92-130-80-52-372-20-19-43-43-35-19-25-179-156-103-35-19-44-46-50-41-41-42-60-62-62-56-59
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedDefinedBenefitPlansAdjustment▇▇▆▆▆▆▇▇▇█▇▇▇▇▇▇▇▆█▅▄▄▇▇▇▂▂▁-18-18-20-20-20-21-16-17-17-14-16-17-17-17-18-18-18-19-14-24-27-27-17-17-17-34-34-36NANA
 us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss▁██▇▄▁▁▁▂▄▄▄▄▄▅▇▅▄▄▄▅▄▄▄▄▄▄▇-23320-2-2-2-10000012100010000002NANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:NetCashProvidedByUsedInOperatingActivities ▆▆▆▇▇▁▅▇▆▅▃▅▇▆▄▅▆▆▄▇█▇▅▆▇369351305527399-387117421388212-1212404112714418430226278511604433235257394NANA449NANA
us-gaap:NetCashProvidedByUsedInInvestingActivities ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▁█▁▁▁▁▁▁-484-528-495-522-375-549-505-472-398-502-514-447-344-414-453-399-315-4613400-604-388-604-614-489-407NANA-246NANA
us-gaap:NetCashProvidedByUsedInFinancingActivities ▇▇▇▆▇█▇▇▇▇▇▇▆▇▇▇▇▇▁▇▆▇▇▇▇179288194-1321610043608717299638196-6415340820720182-3943548-19817937821225NANA-137NANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:NetCashProvidedByUsedInOperatingActivities ▆▆▆▇▇▁▅▇▆▅▃▅▇▆▄▅▆▆▄▇█▇▅▆▇369351305527399-387117421388212-1212404112714418430226278511604433235257394NANA449NANA
us-gaap:ProfitLoss ▆▃▅█▇▅▁▅█▄▅▄▇▆▅▅▇▅▅▄█▆▅▆█75-1396296218-11-33924276-5214-4421188272817959-4-272751543178266NANANANANA
 us-gaap:ProfitLoss us-gaap:StatementEquityComponents us-gaap:RetainedEarnings▆▃▅█▇▅▁▅75-1396296218-11-33924NANANANANANANANANANANA-36268NANANANANANANANANA
us-gaap:DepreciationDepletionAndAmortization ███▇▇▅▄▃▃▃▃▃▃▃▂▂▂▂▂▆▅▄▄▄▄▃▃▃▁▄184182182177175161148144144141143142143141136136132133132167157154153149148144143143126148
us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet 147NANANA27NANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:NetCashProvidedByUsedInInvestingActivities ▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▁█▁▁▁▁▁▁-484-528-495-522-375-549-505-472-398-502-514-447-344-414-453-399-315-4613400-604-388-604-614-489-407NANA-246NANA
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▇▇▇▇▅▇▇▇▆▇▇▆▅▆▆▆▅▆▁█▆██▇▆452492466489353521464462370479484420312391410371301437-67583407586588466386NANA369NANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
us-gaap:NetCashProvidedByUsedInFinancingActivities ▇▇▇▆▇█▇▇▇▇▇▇▆▇▇▇▇▇▁▇▆▇▇▇▇179288194-1321610043608717299638196-6415340820720182-3943548-19817937821225NANA-137NANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value33333333333333333333333333333332222222222
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Par Or Stated Value Per Share

us-gaap:CommonStockParOrStatedValuePerShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value0.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.010.10.010.010.010.010.010.010.010.010.010.01
Percentage of CommonStockParOrStatedValuePerShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Shares Issued

us-gaap:SharesIssued



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value382382373373373372363362337337336325324323319316313676310281281278276274274
Percentage of SharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-05-042018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value38638637737737637636736624341340340329328326322318315983312291283280277275275
Percentage of SharesIssued101.0101.0101.1101.1101.1101.1101.1101.10.0101.2101.1101.1101.1101.1101.1101.0100.8100.7100.6100.6100.5100.5100.4100.4

us-gaap:PreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-31
Value440000.0440000.0440000.0440000.0440000.0420000.0400000.0400000.00.00.00.00.0
Percentage of SharesIssued0.10.10.10.10.10.10.10.10.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-33-3-3333333-3-3-33-3-2-2307-2010-1-1-1-1-1
Percentage of SharesIssued-1.01.0-1.1-1.11.11.11.11.11.21.1-1.1-1.1-1.11.1-1.0-0.8-0.7-0.6-0.6-0.5-0.5-0.4-0.4

Common Stock Shares Issued

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value382382373373373372363362337337336325324323322322321319318317317316315315314313313312311310309284283278281280279278276277276
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Authorized

us-gaap:CommonStockSharesAuthorized



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value600600600600400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400400
Percentage of CommonStockSharesAuthorized100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value384374375374363355338332325325323322322321317317316316315313313312300295293289287285279278277275274
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-312009-09-302009-06-30
Value383374373373363354338331325323322321320318317316315315314312312311290284282280280279278277276275274
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value0.16-0.41-0.020.760.55-0.05-0.950.070.82-0.160.04-0.140.650.280.080.090.560.19-0.02-0.110.850.490.10.250.850.480.160.230.840.430.060.250.680.050.120.140.730.110.120.10.710.32000000000000006-0.05-0.01
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value0.16-0.41-0.020.750.55-0.05-0.950.070.81-0.160.04-0.140.650.270.080.090.560.19-0.02-0.110.850.490.10.250.850.480.160.230.830.430.060.230.660.040.120.140.720.10.120.10.710.32000000000000006-0.05-0.01
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Income Loss From Continuing Operations Per Basic Share

Income Loss From Continuing Operations Per Diluted Share

Revenue From Contract With Customer Excluding Assessed Tax

us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value15251358891969183414368559821717134488399015981197861897143610978171169214916911123133523201076121217829561038
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:MajorCustomers

nix:Commercial



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value389344227236449354221243425
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax25.525.325.524.424.524.725.924.824.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax25.525.325.524.424.524.725.924.824.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Commercial100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Industrial



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value183201196208246212192199237
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax12.014.822.121.513.414.822.520.313.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax12.014.822.121.513.414.822.520.313.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Industrial100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Misc.



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value18171319241891524
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.31.52.01.31.31.11.51.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.31.52.01.31.31.11.51.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Misc.100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Offsystem



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value181716232028202022
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.31.92.41.12.02.42.11.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.31.92.41.12.02.42.11.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Offsystem100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Residential



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value91577843748010948224115021008
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax60.057.349.049.659.657.248.151.258.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax60.057.349.049.659.657.248.151.258.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Residential100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:MajorCustomers, us-gaap:StatementBusinessSegments

nix:Commercial, nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value120115136115119118140116116
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.98.515.311.96.58.316.411.96.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.98.515.311.96.58.316.411.96.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Commercial nix:ElectricOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Commercial, nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2692289012133023580127308
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax17.716.810.212.618.016.49.512.918.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax17.716.810.212.618.016.49.512.918.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Commercial nix:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Industrial, nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value109137151155163145153152162
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.110.117.016.18.910.117.915.59.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.110.117.016.18.910.117.915.59.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Industrial nix:ElectricOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Industrial, nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value746445528266394774
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.94.75.15.54.54.64.64.94.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.94.75.15.54.54.64.64.94.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Industrial nix:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Misc., nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value543665047
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.40.30.70.40.40.00.50.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.40.30.70.40.40.00.50.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Misc. nix:ElectricOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Misc., nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1212912171391016
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.80.91.11.30.90.91.11.01.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.80.91.11.30.90.91.11.01.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Misc. nix:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Misc., us-gaap:CorporateAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value200000.0200000.0200000.0200000.0200000.0100000.0200000.0200000.0200000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Misc. us-gaap:CorporateAndOther100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Offsystem, nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value181716232028202022
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.31.92.41.12.02.42.11.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.31.92.41.12.02.42.11.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Offsystem nix:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Residential, nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value119108148105118112154113114
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.88.016.710.96.57.818.111.56.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.88.016.710.96.57.818.111.56.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Residential nix:ElectricOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:Residential, nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value796670288375975709257389893
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax52.249.332.438.753.249.430.039.752.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax52.249.332.438.753.249.430.039.752.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:Residential nix:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value354366439383408381449386401
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax23.226.949.339.622.326.652.539.323.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax23.226.949.339.622.326.652.539.323.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:ElectricOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1171992451585142610544065951315
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax76.873.050.660.477.773.447.560.676.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax76.873.050.660.477.773.447.560.676.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CorporateAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value200000.0200000.0200000.0200000.0200000.0100000.0200000.0200000.0200000.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:CorporateAndOther100.0100.0100.0100.0100.0100.0100.0100.0100.0

Revenues

us-gaap:Revenues



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value16051241931101018691338895100717501368917990159812978618971436109781711692149169111231335232015961076121217821410956103816581490106812282232175211381171235816859741268
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax105.291.4104.5104.3101.993.2104.6102.5102.0101.8103.8100.0100.0108.4100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value377393467406431403476405423420486
Percentage of Revenues23.531.750.240.223.130.153.240.224.230.753.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax24.729.052.542.023.528.155.741.224.731.355.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:ElectricOperations106.5107.6106.4106.0105.6105.7106.1104.8105.50.00.0

nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value12311006466607144210614216051330951434
Percentage of Revenues76.781.150.160.177.179.347.160.176.069.547.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax80.774.152.462.678.673.949.361.677.570.849.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:GasDistributionOperations105.1101.4103.5103.7101.1100.7103.8101.6101.10.00.0

us-gaap:CorporateAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value10612611711411117111611611414312612112011810410210211298120130143140130128122122131211232
Percentage of Revenues6.710.212.611.36.012.813.011.56.510.513.812.37.59.112.111.47.110.312.010.36.18.512.59.85.511.310.10.812.711.90.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.09.313.111.86.111.913.611.86.710.714.312.37.59.912.111.47.110.312.010.36.18.512.59.85.511.310.10.812.711.90.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:CorporateAndOther53450.063050.058550.057200.055650.0171100.058300.058150.057150.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:IntersegmentElimination



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value-109-129-120-117-114-174-119-119-117-146-130-125-123-118-104-102-102-108-94-151-172-185-170-161-169-151-141-165-151-147
Percentage of Revenues-6.8-10.4-12.9-11.6-6.1-13.0-13.4-11.9-6.7-10.7-14.2-12.7-7.7-9.1-12.1-11.4-7.1-9.9-11.6-13.0-8.0-11.0-15.2-12.1-7.3-14.0-11.7-9.3-15.8-14.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-7.2-9.5-13.5-12.1-6.2-12.2-14.0-12.2-6.8-10.9-14.7-12.7-7.7-9.9-12.1-11.4-7.1-9.9-11.6-13.0-8.0-11.0-15.2-12.1-7.3-14.0-11.7-9.3-15.8-14.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:IntersegmentElimination0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments, us-gaap:Subsegments

nix:ElectricOperations, nix:Unaffiliated



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value377467406430476404423485
Percentage of Revenues23.550.240.223.053.240.224.253.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax24.752.541.923.555.641.224.755.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:ElectricOperations nix:Unaffiliated0.00.00.00.00.00.00.00.0

nix:GasDistributionOperations, nix:Intersegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value33333333333
Percentage of Revenues0.20.30.40.30.20.20.40.30.20.30.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.20.20.40.30.20.20.40.30.20.30.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:GasDistributionOperations nix:Intersegment0.00.00.00.00.00.00.00.00.00.00.0

nix:GasDistributionOperations, nix:Unaffiliated



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value122846360314384186011327431
Percentage of Revenues76.549.859.876.946.859.875.847.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax80.552.062.378.448.961.377.348.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:GasDistributionOperations nix:Unaffiliated0.00.00.00.00.00.00.00.0

us-gaap:CorporateAndOther, nix:Intersegment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value106125116114111171116116114143126
Percentage of Revenues6.610.112.511.35.912.813.011.56.510.513.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.09.313.111.86.111.913.611.86.610.614.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:CorporateAndOther nix:Intersegment0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CorporateAndOther, nix:Unaffiliated



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value200000.0200000.0200000.0200000.0200000.0200000.0200000.0100000.0
Percentage of Revenues0.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:CorporateAndOther nix:Unaffiliated0.00.00.00.00.00.00.00.0

Sales Revenue Net

Cost Of Revenue

Cost Of Goods And Service Excluding Depreciation Depletion And Amortization

us-gaap:CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization



Period End2020-03-312019-03-31
Value462680
Percentage of CostOfGoodsAndServiceExcludingDepreciationDepletionAndAmortization100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax30.337.1

Gross Profit

Operating Expenses

Operating Costs And Expenses

us-gaap:OperatingCostsAndExpenses



Period End2020-03-312019-03-31
Value14571495
Percentage of OperatingCostsAndExpenses100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax95.581.5

General And Administrative Expense

Operating Income Loss

us-gaap:OperatingIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value148-3891463374-78-3151184002709912441622411313838121910916553035115721953334417619342830613720839918514716339925212313940324793111
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.7-2.810.247.820.4-5.5-36.912.123.320.111.312.626.118.813.215.426.520.013.414.124.720.814.016.423.00.016.416.024.00.014.320.10.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value78851408595386134828379125
Percentage of OperatingIncomeLoss53.0-224.7154.618.525.4-492.5-42.769.620.729.3125.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.16.315.88.85.226.915.88.44.85.914.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:ElectricOperations22.223.332.022.323.3101.230.021.320.70.00.0

nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7869-48379275-254-45539321183-15
Percentage of OperatingIncomeLoss53.0-183.2-53.481.873.6324.1144.133.080.367.8-15.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.15.1-5.539.115.0-17.7-53.24.018.713.6-1.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax nix:GasDistributionOperations6.77.0-10.864.719.3-24.1-112.06.624.50.00.0

us-gaap:CorporateAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-8-193-1-13-74-3-48-1-5-13-3-3-38-8-38-28-21-14-6-5-4-4-4-102
Percentage of OperatingIncomeLoss-5.9507.9-1.2-0.31.09.3-1.4-2.6-1.03.0-1.1-4.4-0.31.6-3.0-2.7-1.03.8-8.0-23.6-5.3-6.0-9.1-3.1-1.1-2.7-2.5-1.1-1.0-0.10.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.6-14.2-0.1-0.10.2-0.50.5-0.3-0.20.6-0.1-0.6-0.10.3-0.4-0.4-0.30.8-1.1-3.3-1.3-1.2-1.3-0.5-0.3-0.4-0.4-0.3-0.1-0.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:CorporateAndOther-4400.0-96500.0-550.0-600.01900.0-7300.02200.0-1550.0-2100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Interest Expense

us-gaap:InterestExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value92939594958883889392878785888586909494117111115109109109103102981071031039594899797989898105105
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.16.910.89.75.26.19.79.05.46.910.08.95.37.49.99.66.38.611.610.05.26.89.88.24.79.68.45.511.39.90.00.00.00.00.00.00.00.00.00.00.0

Interest Expense Long Term Debt

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value5-51001-11231-1243133-60556719744134220103-3222020
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.4-0.40.1-0.0-0.00.1-0.21.31.8-0.90.50.40.10.30.4-0.70.00.50.70.60.30.10.80.60.20.41.10.20.20.30.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

Income Loss From Continuing Operations Before Income Taxes Domestic

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value60-136-3369277-165-4343033816516-70332140324629113120-424262365711842977104333311082965369312572743307142-95
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesDomestic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.0-10.1-0.438.115.1-11.5-50.73.119.712.31.9-7.220.811.73.75.120.311.92.5-3.719.814.05.18.818.57.28.618.73.310.40.00.00.00.00.00.00.00.00.00.00.0

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value-87-98-94-94-96-87-118-88-61-105-83-195-84-84-81-92-89-88-89-207-103-114-100-101-104-99-88-94-105-100-103-94-93-86-197-95-95-96-104-102-106
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-5.7-7.3-10.6-9.7-5.2-6.1-13.8-9.0-3.6-7.8-9.4-19.7-5.3-7.1-9.5-10.3-6.3-8.1-10.9-17.8-4.8-6.8-8.9-7.6-4.5-9.2-7.3-5.3-11.1-9.70.00.00.00.00.00.00.00.00.00.00.0

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value-142-107259-153-945622172-2612151817111665-1515082253916227321181137102173010721-5151095449
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.00.2-1.17.43.2-10.7-11.00.63.716.20.3-2.77.64.31.01.97.86.10.7-1.37.04.92.33.07.02.62.76.61.23.60.00.00.00.00.00.00.00.00.00.00.0

Profit Loss

us-gaap:ProfitLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value75-1396296218-11-33924276-5214-4421188272817959-4-272751543178266
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.0-10.30.730.611.9-0.8-39.72.516.1-3.91.6-4.513.27.43.23.212.55.4-0.6-2.412.89.12.85.911.5

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302015-06-302015-03-31
Value75-1396296218-11-33924-36268
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0131.497.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.0-10.30.730.611.9-0.8-39.72.5-3.112.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.0

Comprehensive Income Net Of Tax

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-62-101-42268203-51-31622310-525-602162424-2311143-4-252771453179267
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-4.1-7.5-4.827.711.1-3.6-36.92.318.1-3.90.7-6.113.620.30.5-2.77.74.0-0.6-2.212.98.62.85.911.5

Net Income Loss

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value61-153-7283205-19-34523276-5214-44
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.1-11.3-0.829.211.2-1.4-40.32.416.1-3.91.6-4.5

Assets

us-gaap:Assets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value2259222659221322197421889218042069920307200981996119269188221863518691180671761717471174921705525606248982486623710232572310722653220842162121636218442083820409204452070819742193461947819938195251904819271
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value2259222659221322197421889218042069920307200981996119269188221863518691180671761717471174921705525606248982486623710232572310722653220842162121636218442083820409204452070819742193461947819938195251904819271
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-312008-12-312007-12-31
Value5741598658485976577957505073546345064320436341224191407138113810387238433800650565236175600760286012588657005702569055545410510550804997499050035014492348774894485447285076
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets25.426.426.427.226.426.424.526.922.421.622.621.922.521.821.121.622.222.022.325.426.224.825.325.926.026.025.826.426.325.426.025.024.824.125.325.925.724.725.025.725.20.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-230-92-130-80-52-372-20-19-43-43-35-19-25-35-50-41-41-42-43-65-59-57-45-17211
Percentage of StockholdersEquity-4.0-1.5-2.2-1.4-0.9-0.60.0-0.4-0.4-1.0-1.0-0.9-0.5-0.6-0.9-0.8-0.7-0.7-0.7-0.7-1.2-1.2-1.2-0.9-3.60.2
Percentage of Assets-1.0-0.4-0.6-0.4-0.2-0.20.0-0.1-0.1-0.2-0.2-0.2-0.1-0.1-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.20.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value66716666642664176406640361616151554055295518522551745153507847874764473447154690459741674103405740204011
Percentage of StockholdersEquity116.2111.4109.9107.4110.8111.3121.4112.6123.0128.0126.5126.7123.5126.6132.177.579.378.578.479.782.883.483.483.685.079.0
Percentage of Assets29.529.429.029.229.329.429.830.327.627.728.627.827.827.629.019.320.120.420.420.721.020.120.621.10.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value33333333333333333333322222
Percentage of StockholdersEquity0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value880880880880880880393394000
Percentage of StockholdersEquity15.314.715.014.715.215.37.87.20.00.00.0
Percentage of Assets3.93.94.04.04.04.01.91.90.00.00.0
Percentage of Assets us-gaap:PreferredStock0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-1483-1370-1231-1144-1358-1399-1387-965-919-1073-1020-975-874-972-11231494133913901394128510599179018659011074
Percentage of StockholdersEquity-25.8-22.9-21.1-19.1-23.5-24.3-27.3-17.7-20.4-24.8-23.4-23.7-20.9-23.9-29.224.222.323.123.221.819.118.318.317.819.121.2
Percentage of Assets-6.6-6.0-5.6-5.2-6.2-6.4-6.7-4.8-4.6-5.4-5.3-5.2-4.7-5.2-6.46.05.76.06.05.74.94.44.54.50.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-99-99-99-99-99-99-99-99-99-95-94-94-93-88-79-58-58-58-58-48-40-30-27-25-23-23
Percentage of StockholdersEquity-1.7-1.7-1.7-1.7-1.7-1.7-2.0-1.8-2.2-2.2-2.2-2.3-2.2-2.2-2.1-1.0-1.0-1.0-1.0-0.8-0.7-0.6-0.6-0.5-0.5-0.5
Percentage of Assets-0.4-0.4-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.2-0.2-0.3-0.3-0.2-0.2-0.1-0.1-0.10.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Assets Current

us-gaap:AssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value32251853137815781915205513691315163317631332128014711762137812591395157716372335226124662011205423202159174517072031235218381751197022481860174519852448219518932223
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets14.38.26.27.28.89.46.66.58.18.86.96.87.99.47.67.18.09.09.69.19.19.98.58.810.09.57.97.99.410.88.88.69.610.99.49.010.212.311.29.911.5

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302008-12-312007-12-31
Value20313928231511124168352919172826161523153149642251718382614441013612523811225962910711016842482034
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.90.60.10.10.70.50.20.30.20.10.10.10.20.10.10.10.10.10.21.90.20.10.10.10.20.10.10.20.50.20.10.30.20.10.10.30.30.00.10.00.00.10.00.00.00.0

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value716856539870113210585005849738984805458138474714746476605006721152107063982412711005591716107090752655373085451263810631079517568808
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.23.82.44.05.24.92.42.94.84.52.52.94.44.52.62.73.73.82.92.64.64.32.73.55.54.42.73.34.94.22.52.73.64.12.63.35.55.42.73.04.2

Inventory L I F O Reserve

Inventory Raw Materials And Supplies

us-gaap:InventoryRawMaterialsAndSupplies



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value13012011511110710197991041051029697101100102948684112109106106106104101991141119799998987878784839499102
Percentage of InventoryRawMaterialsAndSupplies100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.60.50.50.50.50.50.50.50.50.50.50.50.50.50.60.60.50.50.50.40.40.40.40.50.50.40.50.50.50.40.50.50.40.40.40.40.40.40.50.50.5

Other Assets Current

us-gaap:OtherAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value18214985103144129891091551326591139130648913310775133187169103320321330246224228357280274277261119100119120103118126
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.80.70.40.50.70.60.40.50.80.70.30.50.70.70.40.50.80.60.40.50.80.70.41.41.41.51.11.01.11.61.31.31.41.30.60.50.60.60.50.60.7

Property Plant And Equipment Gross

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

Property Plant And Equipment Net

Long Term Investments

Investments In Affiliates Subsidiaries Associates And Joint Ventures

us-gaap:InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value1122222455566666666452447452443437407373327279260243215211204204200197202200201141165
Percentage of InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.01.81.81.81.91.91.81.61.51.31.21.11.01.01.01.01.01.01.01.01.00.70.9

Goodwill

us-gaap:Goodwill



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value14851485169016901690169016901690169016901690169016901690169016901690169016903666366636663666366636663666366636663666367736773677367736773677367736773677367736773677
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.66.67.67.77.77.88.28.38.48.58.89.09.19.09.49.69.79.79.914.314.714.715.515.815.916.216.617.016.916.817.618.018.017.818.619.018.918.418.819.319.1

us-gaap:StatementBusinessSegments

nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value1485148516901690169016901690
Percentage of Goodwill100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.66.67.67.77.77.88.2
Percentage of Assets nix:GasDistributionOperations0.010.40.00.00.012.50.0

Intangible Assets Net Excluding Goodwill

Finite Lived Intangible Assets Net

Deferred Tax Assets Liabilities Net

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value35683663405340444022400039383940380136293681367136753661362736043607360935245709569757195456547555195551589659716034613860456140621263045966595560116044605360766050
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets15.816.218.318.418.418.319.019.418.918.219.119.519.719.620.120.520.620.620.722.322.923.023.023.523.924.526.727.627.928.129.030.130.430.430.230.830.930.331.031.931.4

Liabilities Current

us-gaap:LiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value41613745333938134015403634112560322631782566277836643452291126962495265720732524275839543048343133403178300520682974330127272662371836462887255830963649325127173149
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets18.416.515.117.418.318.516.512.616.115.913.314.819.718.516.115.314.315.212.29.911.115.912.914.814.514.013.69.613.715.113.113.018.217.614.613.215.918.316.714.316.3

Accounts Payable Current

us-gaap:AccountsPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value505666494552675883433455497625447451461539352371392433349429563670427459714619369393527538300292380434244316429581242278502
Percentage of AccountsPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.22.92.22.53.14.12.12.22.53.12.32.42.52.91.92.12.22.52.01.72.32.71.82.03.12.71.71.82.42.51.41.41.92.11.21.62.22.91.21.52.6

Taxes Payable Current

us-gaap:TaxesPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value223231157167232222150165212208148152216195130140203183137221287266189216278254181202258235172185237220157179244221168227212
Percentage of TaxesPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.01.00.70.81.11.00.70.81.11.00.80.81.21.00.70.81.21.00.80.91.21.10.80.91.21.10.80.91.21.10.80.91.21.10.80.91.31.10.91.21.1

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value1801441208679585475109901197876826768103114121313317378408347323327308283269309232219239301254230249336270244310
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.80.60.50.40.40.30.30.40.50.50.60.40.40.40.40.40.60.70.71.21.31.51.71.51.41.41.41.31.21.41.11.11.21.51.31.21.31.71.41.31.6

Dividends Payable Current

us-gaap:DividendsPayableCurrent



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value99948294827065058575605353490498208282780787874074680646464064640
Percentage of DividendsPayableCurrent100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.40.40.40.40.40.30.30.00.30.30.30.00.30.30.30.00.30.30.00.30.40.30.00.40.40.30.00.40.30.00.30.30.30.00.30.30.0

Liabilities Noncurrent

us-gaap:LiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value48715071509050744985491051205192507949514821514451905110524752535197504350486745671265806256615761155995628862346167616958815834581257975527544454405430543254585298
Percentage of LiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets21.622.423.023.122.822.524.725.625.324.825.027.327.827.329.029.829.728.829.626.327.026.526.426.526.526.528.528.828.528.228.228.628.428.028.028.127.927.227.828.727.5

Long Term Debt

Deferred Tax Liabilities Noncurrent

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

Minority Interest

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value187218224222218177215184191194187188199200182187188208186270294291297224219216219216225226246242247244193157163162167175152
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.81.01.01.01.00.81.00.91.01.01.01.01.11.11.01.11.11.21.11.11.21.21.31.00.91.01.01.01.01.01.21.21.21.21.00.80.80.80.90.90.8

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-312008-12-312007-12-31
Value5741598658485976577957505073546345064320436341224191407138113810387238433800650565236175600760286012588657005702569055545410510550804997499050035014492348774894485447285076
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets25.426.426.427.226.426.424.526.922.421.622.621.922.521.821.121.622.222.022.325.426.224.825.325.926.026.025.826.426.325.426.025.024.824.125.325.925.724.725.025.725.20.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-230-92-130-80-52-372-20-19-43-43-35-19-25-35-50-41-41-42-43-65-59-57-45-17211
Percentage of StockholdersEquity-4.0-1.5-2.2-1.4-0.9-0.60.0-0.4-0.4-1.0-1.0-0.9-0.5-0.6-0.9-0.8-0.7-0.7-0.7-0.7-1.2-1.2-1.2-0.9-3.60.2
Percentage of Assets-1.0-0.4-0.6-0.4-0.2-0.20.0-0.1-0.1-0.2-0.2-0.2-0.1-0.1-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.20.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value66716666642664176406640361616151554055295518522551745153507847874764473447154690459741674103405740204011
Percentage of StockholdersEquity116.2111.4109.9107.4110.8111.3121.4112.6123.0128.0126.5126.7123.5126.6132.177.579.378.578.479.782.883.483.483.685.079.0
Percentage of Assets29.529.429.029.229.329.429.830.327.627.728.627.827.827.629.019.320.120.420.420.721.020.120.621.10.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value33333333333333333333322222
Percentage of StockholdersEquity0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value880880880880880880393394000
Percentage of StockholdersEquity15.314.715.014.715.215.37.87.20.00.00.0
Percentage of Assets3.93.94.04.04.04.01.91.90.00.00.0
Percentage of Assets us-gaap:PreferredStock0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-1483-1370-1231-1144-1358-1399-1387-965-919-1073-1020-975-874-972-11231494133913901394128510599179018659011074
Percentage of StockholdersEquity-25.8-22.9-21.1-19.1-23.5-24.3-27.3-17.7-20.4-24.8-23.4-23.7-20.9-23.9-29.224.222.323.123.221.819.118.318.317.819.121.2
Percentage of Assets-6.6-6.0-5.6-5.2-6.2-6.4-6.7-4.8-4.6-5.4-5.3-5.2-4.7-5.2-6.46.05.76.06.05.74.94.44.54.50.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-312014-09-302014-06-302014-03-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-99-99-99-99-99-99-99-99-99-95-94-94-93-88-79-58-58-58-58-48-40-30-27-25-23-23
Percentage of StockholdersEquity-1.7-1.7-1.7-1.7-1.7-1.7-2.0-1.8-2.2-2.2-2.2-2.3-2.2-2.2-2.1-1.0-1.0-1.0-1.0-0.8-0.7-0.6-0.6-0.5-0.5-0.5
Percentage of Assets-0.4-0.4-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.5-0.2-0.2-0.3-0.3-0.2-0.2-0.1-0.1-0.10.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value33333333333333333333333333333332222222222
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value-1483-1370-1231-1144-1358-1399-1387-965-919-1073-1020-975-874-972-1060-1067-1042-1123-118215611597149413391390139412851133116411701059925980980917922952978901868899865
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-6.6-6.0-5.6-5.2-6.2-6.4-6.7-4.8-4.6-5.4-5.3-5.2-4.7-5.2-5.9-6.1-6.0-6.4-6.96.16.46.05.76.06.05.75.15.45.44.94.44.84.84.44.74.95.04.54.44.74.5

Treasury Stock Value

us-gaap:TreasuryStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value9999999999999999999594949388878786797979795858585848484848404040403030303027272725
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.40.40.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.50.30.30.20.20.30.30.20.20.20.20.20.20.20.20.10.20.20.20.10.10.10.1

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value-230-92-130-80-52-372-20-19-43-43-35-19-25-179-156-103-35-19-44-46-50-41-41-42-43-60-62-62-65-56-59-60-59-54-54-56-57-57-60-45
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets-1.0-0.4-0.6-0.4-0.2-0.20.0-0.1-0.1-0.2-0.2-0.2-0.1-0.1-1.0-0.9-0.6-0.2-0.1-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.3-0.2

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value-18-18-20-20-20-21-16-17-17-14-16-17-17-17-18-18-18-19-14-24-27-27-17-17-17-17-34-34-36-39-32-26
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax7.820.215.425.439.658.6-648.081.390.532.736.848.388.870.110.311.918.154.471.455.058.254.042.342.040.740.156.355.059.160.354.946.3
Percentage of Assets-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.2-0.2-0.2-0.2-0.1
Percentage of Assets us-gaap:AccumulatedDefinedBenefitPlansAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value-210-77-113-62-32-1320-10-29-28-18-2-6-162-139-86-15-5-20-20-23-23-24-25-25-26-27-27-28-31-34
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax91.383.487.077.761.234.9832.08.11.667.764.352.810.227.590.789.483.044.230.145.044.446.657.559.259.359.244.043.944.543.753.360.1
Percentage of Assets-0.9-0.3-0.5-0.3-0.1-0.10.1-0.0-0.0-0.1-0.1-0.1-0.0-0.0-0.9-0.8-0.5-0.1-0.0-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.2-0.2
Percentage of Assets us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value-23320-2-2-2-100000121000100000002243
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax0.9-3.6-2.5-3.1-0.86.5-84.010.57.9-0.5-1.1-1.11.02.4-0.9-1.3-1.21.4-1.5-0.0-2.6-0.60.2-1.2-0.00.7-0.31.1-3.5-4.0-8.2-6.4
Percentage of Assets-0.00.00.00.00.0-0.0-0.0-0.0-0.00.00.00.0-0.0-0.00.00.00.0-0.00.00.00.00.0-0.00.00.0-0.00.0-0.00.00.00.00.0
Percentage of Assets us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value369351305527399-387117421388212-1212404112714418430226278511604433235257394449480422392-7031983545-118
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax24.225.934.354.421.8-27.013.842.922.615.8-13.824.325.722.75.220.521.123.99.643.728.125.621.019.217.025.20.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value-484-528-495-522-375-549-505-472-398-502-514-447-344-414-453-399-315-4613400-604-388-604-614-489-407-246-294-175-182-367-199-194-151-183
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-31.8-38.9-55.6-53.9-20.5-38.3-59.1-48.1-23.2-37.4-58.3-45.1-21.5-34.6-52.6-44.5-21.9-42.0416.1-51.7-18.1-35.7-54.7-36.7-17.6-13.80.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value179288194-1321610043608717299638196-6415340820720182-3943548-19817937821225-137-158-193-212440-222205-461137
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax11.821.221.9-13.70.969.942.18.91.022.372.219.8-4.112.847.523.11.416.6-482.546.9-9.210.633.715.91.1-7.70.00.00.00.00.00.00.00.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value369351305527399-387117421388212-1212404112714418430226278511604433235257394449480422392-7031983545-118
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax24.225.934.354.421.8-27.013.842.922.615.8-13.824.325.722.75.220.521.123.99.643.728.125.621.019.217.025.20.00.00.00.00.00.00.00.0

Net Income Loss

Profit Loss

us-gaap:ProfitLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value75-1396296218-11-33924276-5214-4421188272817959-4-272751543178266
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.0-10.30.730.611.9-0.8-39.72.516.1-3.91.6-4.513.27.43.23.212.55.4-0.6-2.412.89.12.85.911.5

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302015-06-302015-03-31
Value75-1396296218-11-33924-36268
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0131.497.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.0-10.30.730.611.9-0.8-39.72.5-3.112.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value184182182177175161148144144141143142143141136136132133132167157154153149148144143143126148146134134138141153151149148148148
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Increase Decrease In Other Operating Capital Net

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet



Period End2020-03-312019-03-31
Value14727
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet100.0100.0

Increase Decrease In Inventories

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value-484-528-495-522-375-549-505-472-398-502-514-447-344-414-453-399-315-4613400-604-388-604-614-489-407-246-294-175-182-367-199-194-151-183
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-31.8-38.9-55.6-53.9-20.5-38.3-59.1-48.1-23.2-37.4-58.3-45.1-21.5-34.6-52.6-44.5-21.9-42.0416.1-51.7-18.1-35.7-54.7-36.7-17.6-13.80.00.00.00.00.00.00.00.0

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value452492466489353521464462370479484420312391410371301437-67583407586588466386369292209250216198138191200
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value179288194-1321610043608717299638196-6415340820720182-3943548-19817937821225-137-158-193-212440-222205-461137
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax11.821.221.9-13.70.969.942.18.91.022.372.219.8-4.112.847.523.11.416.6-482.546.9-9.210.633.715.91.1-7.70.00.00.00.00.00.00.00.0

Proceeds From Issuance Of Long Term Debt

Repayments Of Long Term Debt

Payments For Repurchase Of Common Stock

Repayments Of Long Term Debt

Debt Instrument Interest Rate Stated Percentage

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value-0.2450.0559999999999999942.8330.1960.2120.3780.2180.1830.1850.3610.1520.3750.3650.00400000000000000360.2640.3770.3840.0579999999999999960.2820.3580.354-0.0080000000000000070.4510.3350.3790.360.3120.3540.3650.3480.3470.320.4320.346-0.2010.355
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number

Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price

Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period

Share Based Compensation

Deferred Tax Liabilities

Deferred Tax Assets Net

Unrecognized Tax Benefits

Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions

Operating Lease Right Of Use Asset

Cash And Cash Equivalents Period Increase Decrease

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312014-12-31
Value213148373216012153814438283239364549
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Proceeds From Repayments Of Short Term Debt

dei:LegalEntity

nix:BusinessesImpactedbyIncident

nix:ColumbiaOfMassachusetts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value700.00.00.00.0700.0
Percentage of BusinessesImpactedbyIncident100.00.00.00.0100.0

nix:CashFromFinancingActivitiesRelatedToChangeInShortTermBorrowingsDueToSecuritizationTransactions



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value106-9359-21100-9-265160176-21
Percentage of CashFromFinancingActivitiesRelatedToChangeInShortTermBorrowingsDueToSecuritizationTransactions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:CostsResultingfromtheGreaterLawrenceIncident



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value978211031023
Percentage of CostsResultingfromtheGreaterLawrenceIncident100.0100.0100.0100.0100.0

nix:ExpensesOtherThanThirdPartyClaims



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value9322070266
Percentage of ExpensesOtherThanThirdPartyClaims100.0100.0100.0100.0100.0

nix:ExpensesRelatedtoThirdPartyClaims



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value046133757
Percentage of ExpensesRelatedtoThirdPartyClaims0.0100.0100.0100.0100.0

dei:LegalEntity

nix:GasMetersAffected

nix:ColumbiaOfMassachusetts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value7500.00.00.00.07500.0
Percentage of GasMetersAffected100.00.00.00.0100.0

nix:GreaterLawrenceIncidentImpactonOperationandMaintenanceExpense



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value9-5221-332888
Percentage of GreaterLawrenceIncidentImpactonOperationandMaintenanceExpense100.0100.0100.0100.0100.0

nix:ImpairmentAndGainLossOnSaleOfAssetsNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value00000000050
Percentage of ImpairmentAndGainLossOnSaleOfAssetsNet100.0100.0100.0100.0100.0100.0100.00.0100.0100.00.0

nix:IncreaseDecreaseInDeferredChargesAndOtherNonCurrentAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value-120-8-10-5830011
Percentage of IncreaseDecreaseInDeferredChargesAndOtherNonCurrentAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:MiscellaneousNonOperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000-1001-100
Percentage of MiscellaneousNonOperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Range, dei:LegalEntity

nix:PenaltyPerViolationofEmergencyResponsePlan

srt:Maximum, nix:ColumbiaOfMassachusetts



Period End2020-03-31
Value250000.0
Percentage of PenaltyPerViolationofEmergencyResponsePlan100.0

us-gaap:Range, dei:LegalEntity

nix:PenaltyforViolationsofEmergencyResponsePlan

srt:Maximum, nix:ColumbiaOfMassachusetts



Period End2020-03-31
Value20
Percentage of PenaltyforViolationsofEmergencyResponsePlan100.0

nix:PensionandOtherPostretirementNonServiceCost



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2-7-2-3-232660-11
Percentage of PensionandOtherPostretirementNonServiceCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:SecuritizationTransactionFees



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value02000200000
Percentage of SecuritizationTransactionFees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:ServiceAreaByCounty



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value20.00.00.00.020.0
Percentage of ServiceAreaByCounty100.00.00.00.0100.0

us-gaap:CapitalExpendituresIncurredButNotYetPaid



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value150361745123-15-2446145-5-830108-9-175116189-819631311147158
Percentage of CapitalExpendituresIncurredButNotYetPaid100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect



Period End2020-03-312019-12-312019-03-312018-12-31
Value641113967
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect100.0100.0100.0100.0

us-gaap:SubsequentEventType

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:SubsequentEvent



Period End2020-02-20
Value0.21
Percentage of CommonStockDividendsPerShareDeclared100.0

us-gaap:DeferredIncomeTaxesAndTaxCredits



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value-19-2-67451-161-929562107-2110944132210275-59-1513578343714811692996992112723318
Percentage of DeferredIncomeTaxesAndTaxCredits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-1-2000-30000000000
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-8-45-11-11-11-40-10-10-10-12-13-13-13-15-15-15
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses669.22260.02260.02280.02280.01068.41133.31133.31133.31612.51885.71914.31675.02185.71912.51912.5

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0-3000-4-1-1-1-1-1-1-1-1-1-1
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value200000.0200000.00.00.00.0-400000.0-100000.0-100000.0-100000.0-200000.0-100000.0-200000.0-200000.00.00.0-100000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit-40.0-6.2-0.0-0.0-0.010.010.010.010.018.29.118.218.2-0.0-0.08.3

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanContributionsByEmployer

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value65665455597
Percentage of DefinedBenefitPlanContributionsByEmployer100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0000000000277
Percentage of DefinedBenefitPlanContributionsByEmployer12.715.413.111.710.519.012.712.112.77.13794.5

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value313333143334434444
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value2810827272714235363631303030333333
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets788.9830.5824.2824.2824.2955.0956.8978.4981.1795.0770.0774.4757.5774.4772.1772.1

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value319444174444444555
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value13721818186716161616171717222222
Percentage of DefinedBenefitPlanInterestCost346.2376.6377.1379.2379.2381.2381.8377.3377.3381.8380.0390.9382.2409.1407.3407.3

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value2222211111111122
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value2161199771-181777121212
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost74.1672.0456.0388.0388.0388.9400.0100.0-89.5646.21338.5592.3542.9636.8581.0605.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value1511151111111111
Percentage of DefinedBenefitPlanServiceCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value829777317777777777
Percentage of DefinedBenefitPlanServiceCost500.0572.5561.5561.5561.5626.0600.0607.7607.7633.3616.7625.0625.0584.6592.3641.7

us-gaap:DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss



Period End2020-03-312019-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-30
Value-236-80-1-58014312486
Percentage of DisposalGroupIncludingDiscontinuedOperationOperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DividendsCommonStockCash



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value16007474149070701310595711305353990980164642-82-82-157
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value16007474149070701310595711305353990980164642-82-82-157
Percentage of DividendsCommonStockCash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.0100.0100.0100.0100.0100.0

us-gaap:DividendsPreferredStockCash



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value27019828011
Percentage of DividendsPreferredStockCash100.00.0100.0100.0100.00.0100.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value27019828011
Percentage of DividendsPreferredStockCash100.00.0100.0100.0100.00.0100.0

us-gaap:FinancingReceivableAllowanceForCreditLossesRecovery



Period End2020-03-31
Value4
Percentage of FinancingReceivableAllowanceForCreditLossesRecovery100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-31
Value0.0
Percentage of FinancingReceivableAllowanceForCreditLossesRecovery0.0

nix:GasDistributionOperations



Period End2020-03-31
Value4
Percentage of FinancingReceivableAllowanceForCreditLossesRecovery100.0

us-gaap:CorporateAndOther



Period End2020-03-31
Value0.0
Percentage of FinancingReceivableAllowanceForCreditLossesRecovery0.0

us-gaap:FinancingReceivableAllowanceForCreditLossesWriteOffs



Period End2020-03-31
Value7
Percentage of FinancingReceivableAllowanceForCreditLossesWriteOffs100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-31
Value-1000000.0
Percentage of FinancingReceivableAllowanceForCreditLossesWriteOffs-12.7

nix:GasDistributionOperations



Period End2020-03-31
Value-6
Percentage of FinancingReceivableAllowanceForCreditLossesWriteOffs-87.3

us-gaap:CorporateAndOther



Period End2020-03-31
Value0.0
Percentage of FinancingReceivableAllowanceForCreditLossesWriteOffs0.0

us-gaap:GainLossOnSaleOfBusiness



Period End2020-03-312019-03-31
Value-2800
Percentage of GainLossOnSaleOfBusiness100.00.0

us-gaap:GainLossOnSalesOfAssetsAndAssetImpairmentCharges



Period End2020-03-312019-03-31
Value-2800
Percentage of GainLossOnSalesOfAssetsAndAssetImpairmentCharges100.00.0

us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

nix:MassachusettsBusinessDomain



Period End2020-03-31
Value-274
Percentage of GainLossOnSalesOfAssetsAndAssetImpairmentCharges98.0

us-gaap:IncreaseDecreaseInAssetRetirementObligations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value6941084310
Percentage of IncreaseDecreaseInAssetRetirementObligations100.0100.00.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value-1127-1332-3255-11-14-1621-24-145-4-22-6-2574-9-134-140-3-12-25-44
Percentage of IncreaseDecreaseInOtherOperatingLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInRegulatoryAssetsAndLiabilities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value-12152941011480-24-117-703646-69-1466548112814-34-90263-2-11-2-51-18-60-5-50-47-35-17
Percentage of IncreaseDecreaseInRegulatoryAssetsAndLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToContingentlyIssuableShares



Period End2020-03-312019-06-302019-03-312018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value00100000000000000000000000011100
Percentage of IncrementalCommonSharesAttributableToContingentlyIssuableShares100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToEquityForwardAgreements



Period End2020-03-312019-06-302019-03-312018-06-302018-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value0000000081096540
Percentage of IncrementalCommonSharesAttributableToEquityForwardAgreements0.0100.0100.00.00.00.00.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements



Period End2020-03-312019-06-302019-03-312018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value0000000010111-1300000000000000000
Percentage of IncrementalCommonSharesAttributableToShareBasedPaymentArrangements100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InsuranceRecoveries



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312010-12-312010-09-302009-12-312009-09-30
Value01300435100135-1-3-1-6
Percentage of InsuranceRecoveries0.0100.00.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InterestIncomeExpenseNonoperatingNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1221221111100
Percentage of InterestIncomeExpenseNonoperatingNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-50022000-10000-200100-1000000-2000-2
Percentage of OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-13838-49-28-16-2022-2480-9-174153-23-53-69-17-111-90000-11
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value01000-510010000000-6-120-9000011
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax-0.34.2-0.4-0.0-3.125.84.4-30.0-1.2566.7-0.0-0.62.00.3-0.00.2-0.134.8130.0192.30.0100.016.7-150.00.0-200.0-190.0100.0

us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-13336-50-30-19-1521-2510-9-184155-22-53-71-100000000000
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax96.595.3102.2108.2119.971.895.6100.0105.1-300.0101.0105.293.9101.298.7101.5102.660.720.00.00.04.1-0.00.016.7-33.310.07.7

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-50022000-10000-200100-1100001-20
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax3.80.5-1.8-8.2-16.82.40.030.0-3.9-166.7-1.0-4.64.1-1.51.3-1.7-2.44.5-50.0-92.3100.0-4.183.3250.083.3333.3280.0-7.7

us-gaap:OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-13336-50-30-19-3322-135-1-9-164155-22-53-70-90000000000001
Percentage of OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value-13837-49-28-15-3923-1330-8-165153-22-52-68-15022-901110321-1
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value01000-500011000000-5020-9000022
Percentage of OtherComprehensiveIncomeLossNetOfTax-0.53.7-0.8-1.4-5.814.13.4-10.50.6633.3-13.6-1.23.60.5-0.9-0.4-0.432.9-66.7122.710.0107.8100.0-9.118.26.2900.084.4

us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-13336-50-30-19-3322-135-1-9-164155-22-53-70-90000000000
Percentage of OtherComprehensiveIncomeLossNetOfTax96.696.0102.2108.9123.785.196.273.7104.4-433.3114.8105.089.1101.099.6101.9102.961.966.731.845.0-3.3-300.063.654.537.5166.728.1

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-50022000-10000-200100-1000000-20
Percentage of OtherComprehensiveIncomeLossNetOfTax3.90.3-1.4-7.5-17.90.80.436.8-5.0-100.0-1.2-3.87.3-1.51.3-1.5-2.55.2100.0-54.545.0-4.4300.045.527.356.2-966.7-12.5

us-gaap:OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-138-49-28-15-3923-1330-8-165153-22-52-68-15022-9011
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value-138-49-28-15-3923-1330-8-165153-22-52-68-15022-9011
Percentage of OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-31
Value0-10005000-1-100000050-2090000-2-2000
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value0-10001000-100000000100001100
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.00.00.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-03-312010-12-312010-09-302010-03-312009-12-312009-09-30
Value-4412-16-106-1170110-5-10396-14-33-430000000000190-10149
Percentage of OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-03-312011-03-312010-12-312010-09-302010-03-312009-12-312009-09-30
Value-1000000000000-1000000000-100-1000001
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax100.0100.0100.0100.0100.00.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherOperatingActivitiesCashFlowStatement



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value7-19576-13426-15-2261111-10-101370
Percentage of OtherOperatingActivitiesCashFlowStatement100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForProceedsFromOtherInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value0002-311-169-2-330-6-383725221625-212118-751097269101022
Percentage of PaymentsForProceedsFromOtherInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsForRemovalCosts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value3428283025312627193023243130312621
Percentage of PaymentsForRemovalCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfDividendsCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value80747474747070666558575656535349494949828282827878746564646363636363
Percentage of PaymentsOfDividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value819819911000
Percentage of PaymentsOfDividendsPreferredStockAndPreferenceStock100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt



Period End2020-03-312019-12-312019-03-312018-12-312018-09-302017-12-312017-09-30
Value43362518242933
Percentage of PaymentsToAcquireAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementClassOfStock

us-gaap:PreferredStockAmountOfPreferredDividendsInArrears

us-gaap:SeriesAPreferredStock



Period End2020-03-31
Value6
Percentage of PreferredStockAmountOfPreferredDividendsInArrears100.0

us-gaap:PreferredStockDividendsIncomeStatementImpact



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-30
Value13131313138510000
Percentage of PreferredStockDividendsIncomeStatementImpact100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:StatementClassOfStock

us-gaap:PreferredStockDividendsPerShareDeclared

us-gaap:SeriesAPreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value28.250.028.250.028.250.028.88
Percentage of PreferredStockDividendsPerShareDeclared100.00.0100.00.0100.00.0100.0

us-gaap:SeriesBPreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value812.50.0406.25406.25862.150.00.0
Percentage of PreferredStockDividendsPerShareDeclared2876.10.01438.10.03051.90.00.0

us-gaap:StatementClassOfStock

us-gaap:PreferredStockPerShareAmountsOfPreferredDividendsInArrears

us-gaap:SeriesAPreferredStock



Period End2020-03-31
Value16.63
Percentage of PreferredStockPerShareAmountsOfPreferredDividendsInArrears100.0

us-gaap:ProceedsFromIssuanceOfCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-30
Value3233343236360434286396665445657678171733333100
Percentage of ProceedsFromIssuanceOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value-5-5-70-40-30-150-4-9-1300-3000022-1160-80-113113354
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.00.00.0100.00.0100.0100.00.0100.00.0100.0100.0100.0

us-gaap:ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess



Period End2020-03-312019-03-31
Value-226452
Percentage of ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess100.0100.0

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesDebt



Period End2020-03-312019-12-312019-03-312018-12-312018-09-302017-12-312017-09-30
Value45282923113322
Percentage of ProceedsFromSaleOfAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths



Period End2020-03-312019-03-31
Value5000
Percentage of ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths100.00.0

us-gaap:ProvisionForLoanLeaseAndOtherLosses



Period End2020-03-31
Value10
Percentage of ProvisionForLoanLeaseAndOtherLosses100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-31
Value1
Percentage of ProvisionForLoanLeaseAndOtherLosses14.2

nix:GasDistributionOperations



Period End2020-03-31
Value9
Percentage of ProvisionForLoanLeaseAndOtherLosses85.8

us-gaap:CorporateAndOther



Period End2020-03-31
Value0.0
Percentage of ProvisionForLoanLeaseAndOtherLosses0.0

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1022115332432
Percentage of PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PublicUtilitiesRegulatoryProceeding, dei:LegalEntity

us-gaap:PublicUtilitiesApprovedRateIncreaseDecreaseAmount

nix:A2020CEP, nix:ColumbiaOfOhio



Period End2020-02-28
Value18
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount100.0

nix:A2020IRP, nix:ColumbiaOfOhio



Period End2020-02-28
Value32
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount181.8

nix:A2020STRIDE, nix:ColumbiaOfMaryland



Period End2020-01-29
Value1
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount0.0

nix:TDSIC11, nix:NIPSCOGas



Period End2020-02-25
Value-1
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount0.0

us-gaap:PublicUtilitiesRegulatoryProceeding, us-gaap:SubsequentEventType, dei:LegalEntity

nix:A2020STRIDE, us-gaap:SubsequentEvent, nix:ColumbiaOfMaryland



Period End2020-01-29
Value1
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount0.0

nix:DSIC, us-gaap:SubsequentEvent, nix:ColumbiaOfPennsylvania



Period End2020-04-27
Value900000.0
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount0.0

nix:FMCA13, us-gaap:SubsequentEvent, nix:NIPSCOElectric



Period End2020-04-15
Value-1
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount0.0

nix:TDSIC11, us-gaap:SubsequentEvent, nix:NIPSCOGas



Period End2020-02-25
Value-1
Percentage of PublicUtilitiesApprovedRateIncreaseDecreaseAmount0.0

us-gaap:SubsequentEventType, dei:LegalEntity

us-gaap:PublicUtilitiesRequestedRateIncreaseDecreaseAmount

us-gaap:SubsequentEvent, nix:ColumbiaOfPennsylvania



Period End2020-04-24
Value100
Percentage of PublicUtilitiesRequestedRateIncreaseDecreaseAmount100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value00000-1800-140110000021010000111
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value0000000000100000011000000001
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax300.066.7200.0200.080.01.1-25.0-400.0-5.40.073.37.716.750.040.050.028.647.884.622.220.012.5-25.022.240.053.861.573.7

us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedges



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value00000-1800-150010000010000000000
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax0.0-0.0100.00.00.0100.0112.5600.0106.80.026.7107.750.050.060.066.771.452.230.877.890.087.5150.077.8100.053.846.242.1

us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-31
Value-200000.0-100000.0-200000.0-200000.0100000.0200000.0100000.0-100000.0200000.0200000.00.0-200000.0200000.00.00.0-100000.00.00.0-200000.00.0-100000.00.0-100000.00.0-200000.0-100000.0-100000.0-300000.0
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax-200.033.3-200.0-100.020.0-1.112.5-100.0-1.40.00.0-15.433.30.00.0-16.70.00.0-15.40.0-10.00.0-25.00.0-40.0-7.7-7.7-15.8

us-gaap:RegulatedOperatingRevenue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value16051397931101018691461895100717501368917
Percentage of RegulatedOperatingRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value377393467406430403476404423
Percentage of RegulatedOperatingRevenue23.528.250.240.223.027.653.240.224.2

nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value12281003463603143810584186011327
Percentage of RegulatedOperatingRevenue76.571.849.859.876.972.446.859.875.8

us-gaap:CorporateAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value200000.0200000.0200000.0200000.0200000.0100000.0200000.0200000.0200000.0
Percentage of RegulatedOperatingRevenue0.00.00.00.00.00.00.00.00.0

us-gaap:RegulatedOperatingRevenueOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7938404135253924332433
Percentage of RegulatedOperatingRevenueOther100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value222728222221271821
Percentage of RegulatedOperatingRevenueOther28.871.469.455.663.783.769.174.365.2

nix:GasDistributionOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value5611121812412611
Percentage of RegulatedOperatingRevenueOther71.228.630.644.436.316.330.925.734.8

us-gaap:RepaymentsOfLongTermDebtAndCapitalSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-06-302013-03-31
Value43243225522122795022741041362233320423321848835034923427
Percentage of RepaymentsOfLongTermDebtAndCapitalSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths



Period End2020-03-312019-03-31
Value0350
Percentage of RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths0.0100.0

us-gaap:StockIssuedDuringPeriodSharesEmployeeBenefitPlan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value165000.0165000.0146000.0156000.0164000.0194000.0192000.0232000.0264000.0
Percentage of StockIssuedDuringPeriodSharesEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value165000.0165000.0146000.0156000.0164000.0194000.0192000.0232000.0264000.0
Percentage of StockIssuedDuringPeriodSharesEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value46000.048000.051000.052000.050000.057000.055000.064000.047000.052000.052000.054000.049000.0
Percentage of StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value46000.048000.051000.052000.050000.057000.055000.064000.047000.052000.052000.054000.049000.0
Percentage of StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value347000.053000.01000.038000.0426000.062000.05000.074000.0420000.0110000.020000.0-542000.0763000.0
Percentage of StockIssuedDuringPeriodSharesShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value347000.053000.01000.038000.0426000.062000.05000.074000.0420000.0110000.020000.0-542000.0763000.0
Percentage of StockIssuedDuringPeriodSharesShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueEmployeeBenefitPlan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value444444556
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value444444556
Percentage of StockIssuedDuringPeriodValueEmployeeBenefitPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueEmployeeStockPurchasePlan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1111111111111111111111110
Percentage of StockIssuedDuringPeriodValueEmployeeStockPurchasePlan100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value1111111111111111111111110
Percentage of StockIssuedDuringPeriodValueEmployeeStockPurchasePlan100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value0434-23344343343310-12321181668
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value0434-23344343343310-12321181668
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:TaxesExcludingIncomeAndExciseTaxes



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value857467668771586578675756766656507158537910277687310164708662668659679374626486735453
Percentage of TaxesExcludingIncomeAndExciseTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:UtilitiesOperatingExpenseMaintenanceAndOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-30
Value44435939349552804780365402427383391410424336337354349311561574572529533501468452455422394405407402432457382377439451358365
Percentage of UtilitiesOperatingExpenseMaintenanceAndOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

nix:AccruedInsuranceClaimsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-31
Value2416518423525811412
Percentage of AccruedInsuranceClaimsCurrent100.0100.0100.0100.0100.0100.0100.0

nix:CommonDividendsPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value8007474740700
Percentage of CommonDividendsPayableCurrent100.00.0100.0100.0100.00.0100.00.0

nix:CustomerAccountsReceivableBilledLessReserve



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value449466297396692540297477
Percentage of CustomerAccountsReceivableBilledLessReserve100.0100.0100.0100.0100.0100.0100.0100.0

nix:CustomerAccountsReceivableUnbilledLessReserve



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value233346193179284349154356
Percentage of CustomerAccountsReceivableUnbilledLessReserve100.0100.0100.0100.0100.0100.0100.0100.0

nix:DeferredChargesAndOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value1601631571461348611782
Percentage of DeferredChargesAndOther100.0100.0100.0100.0100.0100.0100.0100.0

nix:ExchangeGasPayable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value1859544215855859
Percentage of ExchangeGasPayable100.0100.0100.0100.0100.0100.0100.0100.0

nix:ExchangeGasReceivable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value3948304172883745
Percentage of ExchangeGasReceivable100.0100.0100.0100.0100.0100.0100.0100.0

nix:LegalAndEnvironmentalReserves



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value1720202118182032
Percentage of LegalAndEnvironmentalReserves100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LossContingenciesByNatureOfContingency

nix:LiabilityForEstimatedRemediationCosts

nix:MgpSites



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value861021031059697103106
Percentage of LiabilityForEstimatedRemediationCosts100.0100.0100.0100.0100.0100.0100.0100.0

nix:PreferredDividendsPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value190198190110
Percentage of PreferredDividendsPayableCurrent100.00.0100.0100.0100.00.0100.00.0

nix:PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyAtCostLessAccumulatedDepreciation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value18181818181917286
Percentage of PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyAtCostLessAccumulatedDepreciation100.0100.0100.0100.0100.0100.0100.0100.0

nix:PublicUtilitiesPropertyPlantAndEquipmentPlantInServiceNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value1556816893164621611515722155221515714073
Percentage of PublicUtilitiesPropertyPlantAndEquipmentPlantInServiceNet100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PublicUtilitiesRegulatoryProceeding, dei:LegalEntity

nix:RegulatoryNetCapitalExpendituresIncludedInFiling

nix:A2020CEP, nix:ColumbiaOfOhio



Period End2020-02-28
Value185
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling100.0

nix:A2020IRP, nix:ColumbiaOfOhio



Period End2020-02-28
Value234
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling126.6

nix:A2020STRIDE, nix:ColumbiaOfMaryland



Period End2020-01-29
Value15
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling0.0

nix:TDSIC11, nix:NIPSCOGas



Period End2020-02-25
Value38
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling0.0

us-gaap:PublicUtilitiesRegulatoryProceeding, us-gaap:SubsequentEventType, dei:LegalEntity

nix:A2020STRIDE, us-gaap:SubsequentEvent, nix:ColumbiaOfMaryland



Period End2020-01-29
Value15
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling0.0

nix:DSIC, us-gaap:SubsequentEvent, nix:ColumbiaOfPennsylvania



Period End2020-04-27
Value28
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling0.0

nix:FMCA13, us-gaap:SubsequentEvent, nix:NIPSCOElectric



Period End2020-04-15
Value0.0
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling0.0

nix:TDSIC11, us-gaap:SubsequentEvent, nix:NIPSCOGas



Period End2020-02-25
Value38
Percentage of RegulatoryNetCapitalExpendituresIncludedInFiling0.0

nix:TradeReceivablesAvailableForTransfer



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value593569375468742694410635
Percentage of TradeReceivablesAvailableForTransfer100.0100.0100.0100.0100.0100.0100.0100.0

nix:TradeReceivablesNotTransferred



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value133215115148242295145298
Percentage of TradeReceivablesNotTransferred100.0100.0100.0100.0100.0100.0100.0100.0

nix:TradeReceivablesTransferredNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value459353260320500399265336
Percentage of TradeReceivablesTransferredNet100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsReceivableGrossCurrent



Period End2020-03-312019-12-31
Value736876
Percentage of AccountsReceivableGrossCurrent100.0100.0

us-gaap:AccrualForEnvironmentalLossContingencies



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value91104107108991011071091091111121151091111161201221231251361281281301321351431491561551601621681681731057979
Percentage of AccrualForEnvironmentalLossContingencies100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccruedInsuranceNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value828185828484818683808986858287
Percentage of AccruedInsuranceNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccumulatedDeferredInvestmentTaxCredit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value99101010111111121212121313131414141516161718192020212223242526272930313233353639
Percentage of AccumulatedDeferredInvestmentTaxCredit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AdditionalPaidInCapitalCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value66716666642664176406640361616151554055295518522551745153513551185102507850785065504847874764473447154690467246464627459745794221419841674149413241204103409140804057
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value2019152831211324281817263223193132202038402518293423203231243142453029425537416039
Percentage of AllowanceForDoubtfulAccountsReceivableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetRetirementObligationsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value435416373367358352346334269268268267261262272257253254181204160159175178176174175167165160152149148146140138140138134136138
Percentage of AssetRetirementObligationsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetsFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value172158151150151162201155
Percentage of AssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value172158151150151162201155
Percentage of AssetsFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent



Period End2020-03-312019-12-312015-12-312015-09-302014-12-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-312010-09-302010-06-302009-12-31
Value1655000341000026260001
Percentage of AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent100.00.00.00.0100.00.00.00.00.0100.0100.00.00.00.0100.0

us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

nix:MassachusettsBusinessDomain



Period End2020-03-31
Value1655
Percentage of AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent100.0

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-31
Value2443100023201021
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancialInstrument

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value24431000
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax75.997.795.394.3100.080.0100.0100.0

us-gaap:USTreasuryAndGovernment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value700000.0100000.0200000.0200000.00.0100000.00.00.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax24.12.34.75.70.020.00.00.0

us-gaap:AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-31
Value5000033000010000
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancialInstrument

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value50000320
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax100.050.066.7100.0100.097.193.585.7

us-gaap:USTreasuryAndGovernment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value0.0100000.0100000.00.00.0100000.0200000.0100000.0
Percentage of AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax0.050.033.30.00.02.96.514.3

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value148150141140137141146133
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancialInstrument

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value121118110113115117116106
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis82.079.178.181.084.083.379.779.9

us-gaap:USTreasuryAndGovernment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value2631312622232926
Percentage of AvailableForSaleDebtSecuritiesAmortizedCostBasis18.020.921.919.016.016.720.320.1

us-gaap:DerivativeInstrumentRisk

us-gaap:AvailableForSaleSecurities

us-gaap:AvailableforsaleSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value144154145143138138143130132133139128128131137129136128
Percentage of AvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value00000000000000034273028312424252622232733302932363843
Percentage of AvailableForSaleSecurities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value144154145143138138143130132133139128128131128101991001031039495969986878485696663604237
Percentage of AvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue



Period End2020-03-312019-12-31
Value5412
Percentage of AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue100.0100.0

us-gaap:FinancialInstrument

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value6644323
Percentage of AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue100.0100.0100.0100.0100.0100.0100.0

us-gaap:USTreasuryAndGovernment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value476115214
Percentage of AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue74.6128.3151.1273.8155.6107.4496.7

us-gaap:AvailableForSaleSecuritiesDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value144154145143138138143133
Percentage of AvailableForSaleSecuritiesDebtSecurities100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancialInstrument

us-gaap:CorporateDebtSecurities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value117122114116116114114107
Percentage of AvailableForSaleSecuritiesDebtSecurities81.179.678.681.384.182.979.580.0

us-gaap:USTreasuryAndGovernment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value2731312622232926
Percentage of AvailableForSaleSecuritiesDebtSecurities18.920.421.418.715.917.120.520.0

us-gaap:AvailableForSaleSecuritiesDebtSecuritiesNoncurrent



Period End2020-03-312019-12-31
Value144154
Percentage of AvailableForSaleSecuritiesDebtSecuritiesNoncurrent100.0100.0

us-gaap:CapitalizationLongtermDebtAndEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value1355913842137021308512889128561216812555117931183211881109009781101299907966797779792993316337154271433114404136681365013479127901331912494123731223011912109141126411327113431094110859108421087210823
Percentage of CapitalizationLongtermDebtAndEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312009-12-31
Value237570505911980978746010538695816031075117882488146032100397921105801297433612117686499551344964022923
Percentage of CommercialPaper100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ContractWithCustomerLiabilityCurrent



Period End2020-03-312019-12-31
Value163256
Percentage of ContractWithCustomerLiabilityCurrent100.0100.0

us-gaap:DebtInstrumentCarryingAmount



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312010-12-312009-12-31
Value78257869786471207161715571437690754977967808733864006421667861696169638265769323842084228416817081698135763076876893732676437573658565946147
Percentage of DebtInstrumentCarryingAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLoss



Period End2020-03-312019-12-31
Value-10
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLoss100.00.0

us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPosition



Period End2020-03-312019-12-31
Value017
Percentage of DebtSecuritiesAvailableForSaleUnrealizedLossPosition0.0100.0

us-gaap:DeferredIncomeTaxLiabilitiesNet



Period End2020-03-312019-12-31
Value14511485
Percentage of DeferredIncomeTaxLiabilitiesNet100.0100.0

us-gaap:BalanceSheetLocation

us-gaap:DerivativeAssets

nix:RiskManagementAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value17010612214
Percentage of DerivativeAssets100.0100.0100.0100.0100.0100.0100.0100.0

nix:RiskManagementAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value10346622356
Percentage of DerivativeAssets63.0633.3430.0750.0106.22081.8157.145.5

us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk

nix:RiskManagementAssetsCurrent, nix:CommodityPriceRiskPrograms



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value170100110
Percentage of DerivativeAssets100.0100.0100.0100.013.8100.04.53.4

nix:RiskManagementAssetsCurrent, us-gaap:InterestRateRisk



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value0000502114
Percentage of DerivativeAssets0.00.00.00.086.20.095.596.6

nix:RiskManagementAssetsNoncurrent, nix:CommodityPriceRiskPrograms



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value103466421
Percentage of DerivativeAssets63.0633.3430.0750.0106.2400.011.66.9

nix:RiskManagementAssetsNoncurrent, us-gaap:InterestRateRisk



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value0000018325
Percentage of DerivativeAssets0.00.00.00.00.01681.8145.538.6

us-gaap:DerivativeInstrumentRisk

us-gaap:CashFlowHedging



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value28456132457273121211738497410
Percentage of DerivativeAssets163.0733.3530.0850.0206.22181.8257.10.00.0145.50.00.00.00.00.00.00.00.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value000000000000150
Percentage of DerivativeAssets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value28456132457273121211637430
Percentage of DerivativeAssets163.0733.3530.0850.0206.22181.8257.10.00.0145.50.00.00.00.00.0

us-gaap:FairValueInputsLevel3



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value0.00.00.00.00.00.00.0100000.0200000.00.00.0300000.0400000.00.00.0
Percentage of DerivativeAssets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DerivativeInstrumentsAndHedgesLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value312134125805546454432282858524426422113522
Percentage of DerivativeInstrumentsAndHedgesLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:BalanceSheetLocation

us-gaap:DerivativeLiabilities

nix:RiskManagementLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value1412572445443
Percentage of DerivativeLiabilities100.0100.0100.0100.0100.0100.0100.0100.0

nix:RiskManagementLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value3121341258055464528
Percentage of DerivativeLiabilities2152.41063.5218.9325.41268.2934.0941.766.0

us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentRisk

nix:RiskManagementLiabilitiesCurrent, nix:CommodityPriceRiskPrograms



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value141210104544
Percentage of DerivativeLiabilities100.0100.018.740.3100.0100.0100.010.6

nix:RiskManagementLiabilitiesCurrent, us-gaap:InterestRateRisk



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value00461400038
Percentage of DerivativeLiabilities0.00.081.359.70.00.00.089.4

nix:RiskManagementLiabilitiesNoncurrent, nix:CommodityPriceRiskPrograms



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value5857463833374528
Percentage of DerivativeLiabilities402.8458.782.1154.8759.1744.0941.766.0

nix:RiskManagementLiabilitiesNoncurrent, us-gaap:InterestRateRisk



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value25376784222900
Percentage of DerivativeLiabilities1749.7604.8136.8170.6509.1190.00.00.0

us-gaap:DerivativeInstrumentRisk

us-gaap:CashFlowHedging



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-31
Value3261461821056051504837716862656127122214231
Percentage of DerivativeLiabilities2252.41163.5318.9425.41368.21034.01041.70.00.0166.00.00.00.00.00.00.00.00.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value0000000000031114
Percentage of DerivativeLiabilities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value3261461821056051504837716859635817
Percentage of DerivativeLiabilities2252.41163.5318.9425.41368.21034.01041.70.00.0165.30.00.00.00.00.0

us-gaap:FairValueInputsLevel3



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value000000000000010
Percentage of DerivativeLiabilities0.00.00.00.00.00.00.00.00.00.70.00.00.00.00.0

us-gaap:EmployeeRelatedLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-31
Value129156145134111149153135115195167143107161136124102136125166
Percentage of EmployeeRelatedLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EnergyRelatedInventoryCoal



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value6353382733344953698084102981121101131101068196756448412244393859715475835041445146375259
Percentage of EnergyRelatedInventoryCoal100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EnergyRelatedInventoryNaturalGasInStorage



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value59250294179752863201827128532519479279323199112343398259134445513321973544542667032638525218142746727881298438230384
Percentage of EnergyRelatedInventoryNaturalGasInStorage100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FinancialLiabilitiesFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value32614618210560515071
Percentage of FinancialLiabilitiesFairValueDisclosure100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value32614618210560515071
Percentage of FinancialLiabilitiesFairValueDisclosure100.0100.0100.0100.0100.0100.0100.099.6

us-gaap:FairValueInputsLevel3



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-31
Value0.00.00.00.00.00.00.0300000.0
Percentage of FinancialLiabilitiesFairValueDisclosure0.00.00.00.00.00.00.00.4

us-gaap:FinancingReceivableAllowanceForCreditLosses



Period End2020-03-312019-12-31
Value2013
Percentage of FinancingReceivableAllowanceForCreditLosses100.0100.0

us-gaap:StatementBusinessSegments

nix:ElectricOperations



Period End2020-03-312019-12-31
Value33
Percentage of FinancingReceivableAllowanceForCreditLosses17.723.8

nix:GasDistributionOperations



Period End2020-03-312019-12-31
Value159
Percentage of FinancingReceivableAllowanceForCreditLosses78.370.0

us-gaap:InterestPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value95999590939010810393112891046712071121721297714181140811427513671125681338211670111671146111485130125
Percentage of InterestPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:InvestmentsAndOtherNoncurrentAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value212230219217210206217203206209213201200199207196201194202653656663655639610577529468451437411368361355366350348
Percentage of InvestmentsAndOtherNoncurrentAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LIFOInventoryAmount



Period End2020-03-312019-12-312019-06-302019-03-312018-12-312018-06-302018-03-312017-12-312017-06-302017-03-312016-12-312016-06-302016-03-312015-12-312015-06-302015-03-312014-12-312014-03-312013-12-312012-12-312011-12-312010-12-31
Value29471221471220457204612295092555104548150151
Percentage of LIFOInventoryAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent



Period End2020-03-312019-12-312015-12-312015-09-302014-12-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-312010-09-302010-06-302009-12-31
Value4700003690000300000
Percentage of LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent100.00.0100.00.0100.00.00.00.00.0100.0100.00.00.00.0100.0

us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

nix:MassachusettsBusinessDomain



Period End2020-03-31
Value470
Percentage of LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent100.0

us-gaap:ShortTermDebtType

us-gaap:LineOfCredit

us-gaap:RevolvingCreditFacility



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value5000000000000000000050000
Percentage of LineOfCredit100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0100.00.00.0

us-gaap:StandbyLettersOfCredit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-12-31
Value10101010101010101011131314141414141414141414151414
Percentage of LineOfCredit2.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.02.90.00.00.0

us-gaap:ShortTermDebtType

us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312012-09-302011-06-30
Value150015001500150015001500150015001500150015001500150015001500150015001500150015001500150015001500150015001500500500500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RevolvingCreditFacility



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-03-312013-09-302012-05-31
Value185018501850185018501850185018501850185018501850185018501500150015001500200020001500
Percentage of LineOfCreditFacilityMaximumBorrowingCapacity123.3123.3123.3123.3123.3123.3123.3123.3123.3123.3123.3123.3123.3123.3100.0100.0100.0100.0133.3133.30.0

us-gaap:LongTermDebtAndCapitalLeaseObligations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value78177856785371097110710570947092728675127518677755906058609658575905594861338881795781558397764076387593708976166803681968196806583462676337634059275936596459775969
Percentage of LongTermDebtAndCapitalLeaseObligations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value71310105150485972622842895618093635823112634334424424622661853053054254170895078237667503278303634726718719
Percentage of LongTermDebtAndCapitalLeaseObligationsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LongTermDebtFairValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value8381876488657809753372287280799678628603855080627040706476397185693869757286995896379505933891238944869781728296789783898827849174207369714969726482
Percentage of LongTermDebtFairValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherLongTermInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value66228217215208204214199201204207195194193200190194187195200208210211201203204201189190194196156156150164150136139144128129
Percentage of OtherLongTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Range, us-gaap:ShortTermDebtType

us-gaap:OtherShortTermBorrowings

srt:Maximum, nix:TermLoan



Period End2020-04-012019-04-172018-12-312018-04-18
Value850850600600
Percentage of OtherShortTermBorrowings100.0100.0100.0100.0

us-gaap:ShortTermDebtType

nix:TermLoan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value850850850850600600
Percentage of OtherShortTermBorrowings0.00.00.00.00.0100.0

us-gaap:PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value35937336537237738930031132333739768870071373874675475966563365367542546650852710031020106611079399399469538749199441039102911901134
Percentage of PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementClassOfStock

us-gaap:PreferredStockLiquidationPreference

us-gaap:SeriesBPreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-12-27
Value25000.025000.025000.025000.025000.025000.00.01
Percentage of PreferredStockLiquidationPreference100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementClassOfStock, us-gaap:SubsequentEventType

us-gaap:SeriesAPreferredStock, us-gaap:SubsequentEvent



Period End2023-06-15
Value1000.0
Percentage of PreferredStockLiquidationPreference0.0

us-gaap:PreferredStockParOrStatedValuePerShare



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312018-12-272018-09-302018-06-302015-12-312014-12-312013-12-312012-12-312011-12-31
Value0.010.010.010.010.010.011000.01000.00.010.010.010.010.01
Percentage of PreferredStockParOrStatedValuePerShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PreferredStockSharesOutstanding



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312015-12-312014-12-312013-12-31
Value440000.0440000.0440000.0440000.0440000.0420000.00.00.00.0
Percentage of PreferredStockSharesOutstanding100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:PreferredStockValueOutstanding



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-31
Value8808808808808808803933940
Percentage of PreferredStockValueOutstanding100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value7293760975637461735672577171708370486953690668336701661370207040695768536811971896869578953394449358925692589169907589868956888288058670867286028492
Percentage of PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value15587169121648016133157411554215174148471445614359140421366913288130681285312555122671211111690169081628316017155861508814657143651391213473131181291512542121491190211800115481129511097
Percentage of PublicUtilitiesPropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentPlantInService



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302009-12-31
Value22862245022402623576230792278022328219142137421026206572020619680193681985619578192061894618484262252559325234247752420223695233032286922346219102164221303208882057120337200951978319575194941927419041
Percentage of PublicUtilitiesPropertyPlantAndEquipmentPlantInService100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RegulatoryAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value164225237212190235221174160176203183184248262236226172183175159193200188159142152145141162190192186169142121112151194168238
Percentage of RegulatoryAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RegulatoryAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value19222013199319921979200219071918178416241666165916571636161916011600159915071673168316961440145414941522186319021954202418701899194019781618162216611650164116961644
Percentage of RegulatoryAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RegulatoryLiabilityCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value17716010315015214081121975855831311161071421768312013610262798879607580106171171939911288838792988343
Percentage of RegulatoryLiabilityCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RegulatoryLiabilityNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value20332352244024652488251928262821278027361217122412341265129613201334135013871692167816731675167316771669161516101611159316171615161616631643162416121595156215911558
Percentage of RegulatoryLiabilityNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RestrictedCashAndCashEquivalents



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312011-12-312010-12-31
Value999898121299914109131219292725212416910818292346160202
Percentage of RestrictedCashAndCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShortTermBorrowings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value2046177316152081208019771611600156712058439011514148810591100845567107161314157613111101812698820377113177622532712641359123487012631382724212103
Percentage of ShortTermBorrowings100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ShortTermDebtType

us-gaap:ShortTermDebtWeightedAverageInterestRate

nix:TermLoan



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-03-312017-12-31
Value0.03250.0240.02650.03010.030.03070.02790.03070.0
Percentage of ShortTermDebtWeightedAverageInterestRate100.0100.0100.0100.0100.0100.0100.0100.00.0

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value0.02020.02030.02740.02810.0290.02960.02570.00.02510.01970.0150.01510.01370.01240.01070.01090.010.010.00.00.00960.00820.00670.00630.00550.0070.00670.00690.01020.01110.01020.01160.01010.01010.0098
Percentage of ShortTermDebtWeightedAverageInterestRate62.284.6103.493.496.796.492.10.081.80.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RevolvingCreditFacility



Period End2020-03-312019-12-312017-12-312016-12-312015-12-31
Value0.02130.00.00.00.0
Percentage of ShortTermDebtWeightedAverageInterestRate65.50.00.00.00.0

us-gaap:TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value4593532603205003992650513336262298439310235219385246107141275284205300515265208260444233170193376231193183275
Percentage of TransfersAccountedForAsSecuredBorrowingsAssociatedLiabilitiesCarryingAmount100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Line plots across dimensions of each concept

us-gaap:SharesIssued us-gaap:StatementEquityComponents


us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers


us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments


us-gaap:Revenues us-gaap:StatementBusinessSegments


us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments


us-gaap:StockholdersEquity us-gaap:StatementEquityComponents


us-gaap:StockholdersEquity us-gaap:StatementEquityComponents


us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents