LNT


Line plots across dimensions of each concept
Tables

Table of contents



us-gaap:CommonStockValue

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesAuthorized

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

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

us-gaap:Revenues

us-gaap:CostOfGoodsAndServicesSold
dei:LegalEntity

us-gaap:CostsAndExpenses
dei:LegalEntity

us-gaap:OperatingIncomeLoss
dei:LegalEntity
us-gaap:PublicUtilityRegulatedOrUnregulatedStatus, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments, dei:LegalEntity

us-gaap:InterestExpense
dei:LegalEntity

us-gaap:OtherNonoperatingIncomeExpense
dei:LegalEntity

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
dei:LegalEntity

us-gaap:NonoperatingIncomeExpense
dei:LegalEntity

us-gaap:IncomeTaxExpenseBenefit
dei:LegalEntity

us-gaap:IncomeTaxesPaidNet
dei:LegalEntity

us-gaap:NetIncomeLoss
dei:LegalEntity
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic
dei:LegalEntity
us-gaap:PublicUtilityRegulatedOrUnregulatedStatus, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:Assets
dei:LegalEntity

us-gaap:LiabilitiesAndStockholdersEquity
dei:LegalEntity

us-gaap:StockholdersEquity
dei:LegalEntity
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:AssetsCurrent
dei:LegalEntity

us-gaap:CashAndCashEquivalentsAtCarryingValue
dei:LegalEntity

us-gaap:AccountsReceivableNetCurrent
dei:LegalEntity

us-gaap:InventoryRawMaterialsAndSupplies
dei:LegalEntity

us-gaap:OtherAssetsCurrent
dei:LegalEntity

us-gaap:PropertyPlantAndEquipmentNet
dei:LegalEntity

us-gaap:LongTermInvestments

us-gaap:OtherAssetsNoncurrent
dei:LegalEntity

us-gaap:LiabilitiesCurrent
dei:LegalEntity

us-gaap:LongTermDebtCurrent
dei:LegalEntity

us-gaap:AccountsPayableCurrent
dei:LegalEntity

us-gaap:OtherLiabilitiesCurrent
dei:LegalEntity
us-gaap:FairValueByMeasurementBasis
us-gaap:LongTermDebt
us-gaap:FairValueByMeasurementBasis, dei:LegalEntity

us-gaap:LongTermDebtNoncurrent
dei:LegalEntity

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent
dei:LegalEntity

us-gaap:OtherLiabilitiesNoncurrent
dei:LegalEntity

us-gaap:StockholdersEquity
dei:LegalEntity
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:CommonStockValue

us-gaap:RetainedEarningsAccumulatedDeficit
dei:LegalEntity

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:NetCashProvidedByUsedInOperatingActivities
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInInvestingActivities
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInFinancingActivities
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInOperatingActivities
dei:LegalEntity

us-gaap:NetIncomeLoss
dei:LegalEntity
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:DepreciationDepletionAndAmortization
dei:LegalEntity

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInInvestingActivities
dei:LegalEntity

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInFinancingActivities
dei:LegalEntity

us-gaap:ProceedsFromIssuanceOfLongTermDebt

us-gaap:RepaymentsOfLongTermDebt
us-gaap:DebtInstrument, us-gaap:LongtermDebtType, dei:LegalEntity

us-gaap:RepaymentsOfLongTermDebt
us-gaap:DebtInstrument, us-gaap:LongtermDebtType, dei:LegalEntity

us-gaap:EffectiveIncomeTaxRateContinuingOperations
dei:LegalEntity
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

us-gaap:ProceedsFromRepaymentsOfShortTermDebt
dei:LegalEntity
dei:LegalEntity
lnt:CollectionsReinvestedInReceivables
dei:LegalEntity
lnt:CreditLossesNetOfRecoveries

lnt:IncreaseDecreaseinGasStoredUnderground
dei:LegalEntity
us-gaap:StatementScenario, us-gaap:LongTermContractForPurchaseOfElectricPower
lnt:LongtermContractforPurchaseofElectricPowerBuyoutPayment

us-gaap:AllocatedShareBasedCompensationExpense
dei:LegalEntity

us-gaap:AssetRetirementObligationAccretionExpense
dei:LegalEntity

us-gaap:AssetRetirementObligationLiabilitiesIncurred
dei:LegalEntity

us-gaap:AssetRetirementObligationLiabilitiesSettled
dei:LegalEntity

us-gaap:CapitalExpendituresIncurredButNotYetPaid
dei:LegalEntity

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
dei:LegalEntity

us-gaap:CommonStockDividendsPerShareDeclared
us-gaap:ConcentrationRiskByBenchmark
us-gaap:ConcentrationRiskPercentage1
us-gaap:ConcentrationRiskByBenchmark, dei:LegalEntity

us-gaap:ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset
dei:LegalEntity

us-gaap:CumulativeEffectOnRetainedEarningsNetOfTax1
us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents

us-gaap:DeferredIncomeTaxesAndTaxCredits
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType, dei:LegalEntity
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit
us-gaap:RetirementPlanType, dei:LegalEntity
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType, dei:LegalEntity
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType, dei:LegalEntity
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost
us-gaap:RetirementPlanType, dei:LegalEntity
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanServiceCost
us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:DepreciationAndAmortization
dei:LegalEntity
us-gaap:Energy, us-gaap:TradingActivityByType
us-gaap:DerivativeNonmonetaryNotionalAmountEnergyMeasure
us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity
us-gaap:Energy, us-gaap:TradingActivityByType
us-gaap:DerivativeNonmonetaryNotionalAmountMass
us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity
us-gaap:Energy, us-gaap:TradingActivityByType
us-gaap:DerivativeNonmonetaryNotionalAmountVolume
us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity

us-gaap:DividendsCommonStock
dei:LegalEntity
us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:DividendsPreferredStock
dei:LegalEntity

us-gaap:EarningsPerShareBasicAndDiluted

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense
dei:LegalEntity
us-gaap:Range, us-gaap:PublicUtility
us-gaap:EnvironmentalExitCostsAnticipatedCost
us-gaap:Range, us-gaap:PublicUtility, dei:LegalEntity
us-gaap:FairValueByAssetClass
us-gaap:FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
us-gaap:FairValueByAssetClass, dei:LegalEntity
us-gaap:FairValueByAssetClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
us-gaap:FairValueByAssetClass, dei:LegalEntity
us-gaap:FairValueByAssetClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
us-gaap:FairValueByAssetClass, dei:LegalEntity
us-gaap:FairValueByAssetClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
us-gaap:FairValueByAssetClass, dei:LegalEntity

us-gaap:IncomeLossFromEquityMethodInvestments
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:IncreaseDecreaseInAccountsPayable
dei:LegalEntity

us-gaap:IncreaseDecreaseInAccountsReceivable
dei:LegalEntity

us-gaap:IncreaseDecreaseInDeferredIncomeTaxes
dei:LegalEntity

us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations

us-gaap:IncreaseDecreaseInRegulatoryLiabilities
dei:LegalEntity

us-gaap:InterestPaidNet
dei:LegalEntity

us-gaap:LongTermPurchaseCommitmentAmount

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherCostAndExpenseOperating

us-gaap:OtherNoncashIncomeExpense
dei:LegalEntity

us-gaap:PaymentsForProceedsFromOtherInvestingActivities
dei:LegalEntity

us-gaap:PaymentsOfDividendsCommonStock
dei:LegalEntity

us-gaap:PaymentsToAcquireOtherProductiveAssets

us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivables
dei:LegalEntity
dei:LegalEntity
us-gaap:ProceedsFromContributionsFromParent
us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:ProceedsFromIssuanceOfCommonStock
us-gaap:StatementEquityComponents
us-gaap:SubsidiarySaleOfStock
us-gaap:DebtInstrument, us-gaap:LongtermDebtType, dei:LegalEntity
us-gaap:ProceedsFromIssuanceOfDebt
us-gaap:DebtInstrument, us-gaap:LongtermDebtType, us-gaap:SubsequentEventType, dei:LegalEntity

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities
dei:LegalEntity
us-gaap:Range, dei:LegalEntity
us-gaap:ProceedsFromSaleAndCollectionOfReceivables

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions
dei:LegalEntity

us-gaap:RegulatedAndUnregulatedOperatingRevenue
dei:LegalEntity
us-gaap:PublicUtilityRegulatedOrUnregulatedStatus, us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments
us-gaap:StatementBusinessSegments, dei:LegalEntity

us-gaap:RegulatedOperatingRevenueElectricNonNuclear
dei:LegalEntity

us-gaap:RegulatedOperatingRevenueGas
dei:LegalEntity

us-gaap:RegulatedOperatingRevenueOther
dei:LegalEntity
us-gaap:CounterpartyName, us-gaap:RelatedPartyTransaction, us-gaap:RelatedPartyTransactionsByRelatedParty
us-gaap:RelatedPartyTransactionAmountsOfTransaction
us-gaap:CounterpartyName, us-gaap:RelatedPartyTransaction, us-gaap:RelatedPartyTransactionsByRelatedParty, dei:LegalEntity
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

us-gaap:ShortTermDebtWeightedAverageInterestRateOverTime
dei:LegalEntity

us-gaap:ShorttermDebtAverageOutstandingAmount
dei:LegalEntity

us-gaap:ShorttermDebtMaximumAmountOutstandingDuringPeriod
dei:LegalEntity
us-gaap:SubsidiarySaleOfStock
us-gaap:StockIssuedDuringPeriodSharesNewIssues

us-gaap:StockholdersEquityOther
us-gaap:StatementEquityComponents

us-gaap:TaxesExcludingIncomeAndExciseTaxes
dei:LegalEntity

us-gaap:UnregulatedOperatingRevenue

us-gaap:UtilitiesOperatingExpenseFuelUsed
dei:LegalEntity

us-gaap:UtilitiesOperatingExpenseGasAndPetroleumPurchased
dei:LegalEntity
dei:LegalEntity
us-gaap:UtilitiesOperatingExpenseMaintenanceAndOperations

dei:EntityCommonStockSharesOutstanding
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:AllowanceForDoubtfulAccountsReceivableSold
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:CashProceedsFromReceivablesSold

lnt:CommonStockHeldInTrustShares

lnt:CommonStockHeldInTrustWeightedAverageValuePerShare
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:CustomerAccountsReceivableSoldAmount
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:DeferredProceedsOfReceivablesSold
us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis, dei:LegalEntity

lnt:FairValueOfDeferredProceedsOfReceivablesSold
dei:LegalEntity
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity

lnt:InvestmentsBusinessLine1
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:OtherReceivablesSoldAmount
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:ReceivablesSold
us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity
lnt:UnbilledUtilityRevenuesSoldAmount
dei:LegalEntity
us-gaap:AccountsPayableRelatedPartiesCurrent

us-gaap:AccountsReceivableGrossCurrent
dei:LegalEntity
us-gaap:PublicUtility
us-gaap:AccrualForEnvironmentalLossContingencies
us-gaap:PublicUtility, dei:LegalEntity

us-gaap:AdditionalPaidInCapitalCommonStock
dei:LegalEntity

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent
dei:LegalEntity

us-gaap:AssetRetirementObligation
dei:LegalEntity

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations
dei:LegalEntity

us-gaap:CommercialPaper
dei:LegalEntity

us-gaap:CommonStockHeldInTrust

us-gaap:DeferredCosts
dei:LegalEntity

us-gaap:DeferredCreditsAndOtherLiabilities
dei:LegalEntity

us-gaap:DeferredIncomeTaxLiabilitiesNet
dei:LegalEntity
us-gaap:StatementScenario, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear
us-gaap:StatementScenario, us-gaap:RetirementPlanType, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeAssets
us-gaap:DerivativeInstrumentRisk, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeAssetsCurrent
us-gaap:DerivativeInstrumentRisk, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeAssetsNoncurrent
us-gaap:DerivativeInstrumentRisk, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeLiabilities
us-gaap:DerivativeInstrumentRisk, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis
us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeLiabilitiesCurrent
us-gaap:DerivativeInstrumentRisk, dei:LegalEntity
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeLiabilitiesNoncurrent
us-gaap:DerivativeInstrumentRisk, dei:LegalEntity
us-gaap:Energy, us-gaap:TradingActivityByType
us-gaap:DerivativeNonmonetaryNotionalAmount
us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
dei:LegalEntity

us-gaap:EnergyRelatedInventoryGasStoredUnderground
dei:LegalEntity

us-gaap:EnergyRelatedInventoryOtherFossilFuel
dei:LegalEntity
us-gaap:Energy, us-gaap:FairValueByAssetClass
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
us-gaap:Energy, us-gaap:FairValueByAssetClass, dei:LegalEntity
us-gaap:FairValueByAssetClass
us-gaap:FairValueByAssetClass, dei:LegalEntity
dei:LegalEntity
us-gaap:FinanceLeaseLiabilityNoncurrent
us-gaap:GuaranteeObligationsByNature
us-gaap:GuaranteeObligationsMaximumExposure
us-gaap:GuaranteeObligationsByNature, dei:LegalEntity
us-gaap:Ownership
us-gaap:ConsolidatedEntities, us-gaap:StatementScenario
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity
us-gaap:StatementScenario, dei:LegalEntity

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity
dei:LegalEntity

us-gaap:LongTermDebtFairValue
dei:LegalEntity
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity

us-gaap:MoneyMarketFundsAtCarryingValue
dei:LegalEntity
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity
us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis, dei:LegalEntity
us-gaap:IncomeTaxAuthority
us-gaap:OperatingLossCarryforwards
us-gaap:IncomeTaxAuthority, dei:LegalEntity

us-gaap:OtherLongTermInvestments

us-gaap:OtherReceivables
dei:LegalEntity

us-gaap:OtherShortTermBorrowings
dei:LegalEntity

us-gaap:RegulatoryAssets

us-gaap:RegulatoryAssetsCurrent
dei:LegalEntity

us-gaap:RegulatoryAssetsNoncurrent
dei:LegalEntity

us-gaap:RegulatoryLiabilities

us-gaap:RegulatoryLiabilityCurrent
dei:LegalEntity

us-gaap:RegulatoryLiabilityNoncurrent
dei:LegalEntity
us-gaap:CounterpartyName, us-gaap:RelatedPartyTransaction, us-gaap:RelatedPartyTransactionsByRelatedParty
us-gaap:RelatedPartyTransactionDueFromToRelatedParty
us-gaap:CounterpartyName, us-gaap:RelatedPartyTransactionsByRelatedParty, dei:LegalEntity
us-gaap:StatementScenario, us-gaap:SubsidiarySaleOfStock
us-gaap:SharesIssuedPricePerShare
us-gaap:SubsidiarySaleOfStock

us-gaap:ShortTermBorrowings
dei:LegalEntity

us-gaap:ShortTermDebtWeightedAverageInterestRate
dei:LegalEntity

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
dei:LegalEntity
us-gaap:IncomeTaxAuthority
us-gaap:TaxCreditCarryforwardAmount
us-gaap:IncomeTaxAuthority, dei:LegalEntity

us-gaap:UnbilledReceivablesCurrent
dei:LegalEntity

us-gaap:WeightedAverageRateDomesticDepositMoneyMarket
dei:LegalEntity

Tables

  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:CommonStockValue ████████████████▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁22222222222222221111111111111111111111NANANA
us-gaap:CommonStockSharesOutstanding ███▇▇▇▇▇▇▇▇▇▇▇▇▇▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁249245240237237236235233231231231231227227227227113113113113112110110110110110110110110110110110110111110110110110NANANA
us-gaap:CommonStockSharesAuthorized ████████████████▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁480480480480480480480480480480480480480480480480240240240240240240240240240240240240240240240240240240240240240240NANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding 244NA239238236NA235232231NANANANANANANANANANANANANANANANANA110110110NA110110110NA110110110NA110110110
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic 244NA239237236NA235232231NANANANANANANANANANANANANANANANANA110110110NA110110110NA110110110NA110110110
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax ▆▅▇▃▇▅▆▄▆▅▆▃▄▃▆▂▄▂▅▂▅▃▄▂▇▄▅▂▅▂▅▁▃▅█▄▆▄▇▂▅9158809907909878739288169168569067658537979247548437408987178978048437509528328667188597508876907658791021819945832951741890
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax dei:LegalEntity lnt:Ipl▆▅█▃▇▅▇▄▆▄▆▃▄▃▆▃▄▂▅▂▅▃▄▃▆▄▅▂▄▂▅▁▂▂▅▁▄▃▆▂▄518496596441555494547474525472527420450434516411458398504382489431476411528463494383477393497360398404484374477417534389454
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax dei:LegalEntity lnt:Wpl▅▄▅▂█▅▅▂▆▅▅▂▇▄▇▂▅▂▆▂▇▄▄▂█▄▄▁▅▃▅▁▄▃▅▂▆▃▅▁▆375362372326415369370330381374370334393352397334375330382324397359354324410355360319369345376315354344374326388348369312392
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments lnt:RetailCommercial,lnt:Electric182NA230171181173215172174173205165165NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments lnt:RetailIndustrial,lnt:Electric209NA263214208213247225201206243207195NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments lnt:RetailResidential,lnt:Electric266NA331233274242312248259239296229241NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:RetailCommercial,lnt:Electric,lnt:Ipl119NA158111116NA146114NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:RetailIndustrial,lnt:Electric,lnt:Ipl121NA157118116NA141128NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:RetailResidential,lnt:Electric,lnt:Ipl147NA196125147NA180139NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:MajorCustomers,us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:RetailResidential,lnt:Electric,lnt:Wpl119NA135107127NA132109NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments lnt:Electric730NA915691743704861726708695840680677666864675668623835640671622771643675NA798612633NA815612572NA796NA620NA842NANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments lnt:Gas152NA41652151474468185138456215410639571529338511981524776240NA3973197NA4650167NA46NA229NA46NANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:Electric,lnt:Ipl424NA560392419NA509422NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:Electric,lnt:Wpl305NA355298323NA352304NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:Revenues ▆▅▇▃▇▅▆▄▆▅▆▃▄▃▆▂▄▂▅▂▅▃▄▂▇▄▅▂▅▂▅▁▃▅█▄▆▄▇▂▅9158809907909878739288169168569067658537979247548437408987178978048437509528328667188597508876907658791021819945832951741890
us-gaap:CostOfGoodsAndServicesSold ▅▃▇▁▆▄█▄122118127112123120129119NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CostOfGoodsAndServicesSold dei:LegalEntity lnt:Ipl▄▄█▁▆▄█▄8483917787849284NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CostOfGoodsAndServicesSold dei:LegalEntity lnt:Wpl█▁▁▁▁▁▄▁3735353535353635NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:CostsAndExpenses ▅▅▄▂█▆▃▃▆▅▃▁▅▄▆▂▄▃▃▁▆▅▂▂█727719700640810752672664750726675616711697762626697660663608744712648647798NA665614738NA673581670NA836747817NA705640781
 us-gaap:CostsAndExpenses dei:LegalEntity lnt:Ipl▅▅▅▂█▆▄▄▆▅▃▁▄▄▃▂▄▂▃▁▅▄▃▃▇422415423366481439404397450423395353400399390363396373387348423407382377471NA394348436NA385325374NA368355430NA379344NA
 us-gaap:CostsAndExpenses dei:LegalEntity lnt:Wpl▄▄▂▁▇▇▂▂▅▆▃▂▆▅▄▁▅▄▃▁▇▆▁▂█281288263259317308266267297301279261307294282259296281272256316300260264322NA265260297NA283254289NA287281313NA282260NA
us-gaap:OperatingIncomeLoss ▅▄█▃▄▃▇▄▄▃▆▃▃▂▄▃▃▁▆▂▄▂▅▂▄▂▅▂▃▂▆▂▂▂▅▁▃▂▇▂▂18816029014917612125615116512923114914299162128145792351091529119410315410820110312010121310895931857212799246100109
 us-gaap:OperatingIncomeLoss dei:LegalEntity lnt:Ipl▅▄█▄▃▃▇▄▄▂▆▃▂▂▆▂▃▁▅▂▃▁▄▂▃▂▅▂▂▁▅▂▁▁▅▁▂▁▇▂▂9681173747354143777549131664934125486225117336523933457361003441291123523261161847221554538
 us-gaap:OperatingIncomeLoss dei:LegalEntity lnt:Wpl▆▄▇▃▆▃▇▃▅▄▆▄▅▂█▄▄▁█▃▄▂▆▂▅▃▆▂▄▃▆▃▃▄▅▁▄▄▅▂▃93731086798611046384729073865811575784911068805993608767955972659361647386457470865269
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments lnt:Electric146NA2831321261002481341261112321351079824411910975232100104681908994NA1998573NA2039159NA206NA89NA241NANA
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments lnt:Gas41NA-474518-253115-23283-31286-5-23612-4243NA-3537NA0327NA-2NA35NA-2NANA
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments lnt:UtilityBusiness▅▄█▃▄▂▇▃▄▃▆▃▃▂▇▃▃▁▆▂▃▁▅▂▃19015528114117111524714115912222214013593240123140742271021468318794145NA19594113NA2059688NA203NA121NA242NANA
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:Electric,lnt:Ipl67NA1756846NA14473NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:Electric,lnt:Wpl79NA1086479NA10461NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:OperatingIncomeLoss us-gaap:StatementBusinessSegments,dei:LegalEntity lnt:Gas,lnt:Ipl27NA-4426NA-32NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:InterestExpense ████▇▆▆▆▅▄▄▃▃▃▂▂▂▂▂▂▂▁▁▁▁68696869666363615956535252514848484746464645444545NA424242NA383838NA384040NA413940
 us-gaap:InterestExpense dei:LegalEntity lnt:Ipl██▆▆▅▅▆▆▅▅▄▄▄▄▃▃▃▃▂▂▃▂▁▂▂34343131292830302928272727272525242523232422212222NA191919NA191919NA191919NA2120NA
 us-gaap:InterestExpense dei:LegalEntity lnt:Wpl▇▅▇█▇▅▅▅▅▅▄▄▂▂▂▂▂▂▄▄▄▄▁▁▁25242526252424242424232322222222222223232323212121NA212121NA191920NA192020NA2018NA
us-gaap:OtherNonoperatingIncomeExpense ▅▂▂▂▁▅▅▄▄▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇█-1-3-3-3-4-1-1-2-20000000000000001NA000NA001NA000NA000
 us-gaap:OtherNonoperatingIncomeExpense dei:LegalEntity lnt:Ipl█▄▁▄▄████████████████▁███0-1-2-1-10000000000000000-2000NA000NA000NA000NA00NA
 us-gaap:OtherNonoperatingIncomeExpense dei:LegalEntity lnt:Wpl█▁▁▁▁▁▁▁▁████████████████████0-1-1-1-1-1-1-1-100000000000000000000NANA00NANA0NANA00NA
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest ▅▄█▃▄▃▇▃▄▃▆▃▃▂▄▃▄▁▇▂▃▁▅▂▄15313325110814293219116140981971181197713810512148210821196017077131NA1797895NA1928671NA16043100NA219NANA
 us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest dei:LegalEntity lnt:Ipl▄▄█▃▄▃▇▃▃▂▆▃▂▂▆▂▃▁▆▂▃▁▅▂▃71601504958381235652261084436231143547910016465781741NA861925NA94175NA98028NA135NANA
 us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest dei:LegalEntity lnt:Wpl▆▄▇▃▆▂▆▂▄▃▅▃▄▂█▄▅▁█▃▄▂▆▃▆8159924980468646655572546548103646934101586647855281NA885164NA875557NA783665NA79NANA
us-gaap:NonoperatingIncomeExpense ▄▆▂▁▄▆▃▄▇▅▄▅████▇▅▇▇▄▅▇▇█-34-27-38-41-34-28-36-34-25-31-34-31-23-22-23-23-24-30-25-26-33-30-24-25-23NA-22-24-25NA-21-22-24NA-25-27-26NA-27-25-26
us-gaap:IncomeTaxExpenseBenefit ▁▇▇▆▆▅▆▆▆▄█▇▆▆▅▇▇▅█▆▇▄▆▆▇-181923111551113161262117127182110271120-1121320NA171012NA391627NA34-1022NA642334
us-gaap:IncomeTaxesPaidNet ▆▁▆▇▄▆▆▇▆▆▆█▆▆▇▇▆▆▆▆▆▆▆▆▅0-1914-600500092144000000-10-3NANANA2NANANA0NANANA-3NANANA0
 us-gaap:IncomeTaxesPaidNet dei:LegalEntity lnt:Ipl▄▄▄▃▃█▄▄▄▅▄▁▄▆▁▇▄▆▁▁▃▄▁▂▄013-5-6211004-1-14211-1314-111-12-12-60-12-101NANANA4NANANA-14NANANA22NANANANA
us-gaap:NetIncomeLoss ▆▄█▃▄▃▇▃▄▃▆▃▃▂▄▃▃▁▆▂▃▂▅▂▄172114228971278720810212396171961036513186993618270996215564110NA1606780NA1546938NA1255579NA1535248
 us-gaap:NetIncomeLoss dei:LegalEntity lnt:Ipl▅▃█▃▄▃▇▄▃▂▇▃▃▂▇▃▃▁▇▂▃▂▆▂▃▂▆▂▃▂▆▂▁▁▆▁▂▂▆▂▁85471434755411295449181234539261163448812019502210520462111224312510619-1910112711100219
 us-gaap:NetIncomeLoss dei:LegalEntity lnt:Wpl█▄▆▃▅▃▇▃▄▄▄▃▃▂▆▃▃▁▆▃▃▂▅▂▄▃▅▂▃▃▄▂▂▃▄▁▃▂▄▂▂8949754265387639545349384532694347246739442961345438613443415636314251254435503037
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Wpl89NANANA65NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic ▆▄█▃▄▃▇▃▄▃▆▃▃▂▄▃▃▁▆▂▃▂▅▂▄▂▅▂▂▂▅▂▁▂▄▂▂▁▅▁▁170111226941258520510012093168941006212883963417967966015361108651576569681506534571225173471494743
 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic dei:LegalEntity lnt:Ipl▅▃█▃▄▃▇▄▃▂▇▃▃▂▇▃▃▁▇▂▃▂▆▂▃▂▇▂▂▂▆▂▁▁▆▁▂▂▆▂▁82441414553391265146161204237241143145511716472010218431811022222210316-4698-221896175
 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:StatementBusinessSegments lnt:UtilityBusiness▆▃█▃▄▃▇▃▄▂▇▃▃▂▇▃▃▁▇▂▃▂▆▂▄17294216871197720291100491768789551837592291845592491645398NA1715664NA1595126NA148NA65NA146NANA
 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:StatementEquityComponents us-gaap:RetainedEarnings▅▂█▁▃▁▇▂▃1701112269412585205100120NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Ipl▄▁█▁▂▁▇▂824414145533912651NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:Assets ███▇▇▇▇▆▆▆▅▅▅▅▄▄▄▄▄▄▄▄▃▃▃▃▃▂▂▂▂▂▁▁▁▁▁▁168791670016533161211571315426152691461514241141871411413743134641337313029126851253512495125581231212079120851159411386111161111210981108871073310785102509934962896879481930194009282NANANA
 us-gaap:Assets dei:LegalEntity lnt:Ipl███▇▇▆▆▆▅▅▅▅▅▅▅▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁940492779302883086478411837878497627760676827507732373047161679667136709677965876414646161946000583058065693561155305457539952015066509349604886NA4937NANANA
 us-gaap:Assets dei:LegalEntity lnt:Wpl██▇█▇▇▇▆▆▆▅▅▅▅▅▅▅▅▅▄▄▄▄▄▃▃▃▃▃▃▂▂▁▁▁▁655165066313639061656152604459105757575655945456533552905405534653055270526352025166512849064885481348044816478247174762425741564058404439363874NA3889NANANA
us-gaap:LiabilitiesAndStockholdersEquity ███▇▇▇▇▆▆▆▅▅▅▅▄▄▄▄▄▄▄▄▃▃▃▃▃▂▂▂▂▂▁▁▁▁▁▁168791670016533161211571315426152691461514241141871411413743134641337313029126851253512495125581231212079120851159411386111161111210981108871073310785102509934962896879481930194009282NANANA
 us-gaap:LiabilitiesAndStockholdersEquity dei:LegalEntity lnt:Ipl███▇▇▆▆▆▅▅▅▅▅▅▅▄▄▄▄▄▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁940492779302883086478411837878497627760676827507732373047161679667136709677965876414646161946000583058065693561155305457539952015066509349604886NA4937NANANA
 us-gaap:LiabilitiesAndStockholdersEquity dei:LegalEntity lnt:Wpl██▇█▇▇▇▆▆▆▅▅▅▅▅▅▅▅▅▄▄▄▄▄▃▃▃▃▃▃▂▂▁▁▁▁655165066313639061656152604459105757575655945456533552905405534653055270526352025166512849064885481348044816478247174762425741564058404439363874NA3889NANANA
us-gaap:StockholdersEquity █▇▇▆▆▆▅▅▅▄▄▄▄▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁55025205496946994682458545704350423141824154405038963862385937903764372437453620359734383435333733313281326631603145313431163014299730133001292729202893NANANA
 us-gaap:StockholdersEquity dei:LegalEntity lnt:Ipl██▇▇▇▇▆▆▅▅▅▅▄▄▄▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁339532713244314531423030283826542514250924322351224722492137203620421995199119081826181418291731171816791663155515351519149813951360139413631294NA1389NANANA
 us-gaap:StockholdersEquity dei:LegalEntity lnt:Wpl██▇▆▆▆▆▅▄▄▄▃▃▃▄▄▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▁▁▁▁▁243623632324218521792149214620551900188118091751174417301813177817691756175917231716170317041672166716421633160115951583148014521445144214291406NA1369NANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital█▆▄▃▃▃▃▂▁▁2674244522362108210020452038194718511845NANANA1693NANANA1663NANANA1509NANANA1507NANANA1511NANANA1510NANANA1506NANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:RetainedEarnings█▇▇▅▄▄▄▂▂▁2833276527392597258725452539241223892346NANANA2177NANANA2068NANANA1938NANANA1780NANANA1630NANANA1510NANANA1394NANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:AdditionalPaidInCapital,lnt:Ipl█▇▇▇▇▆▃▂▁▁2447234723222322232222222027192717971797NANANA1597NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:AdditionalPaidInCapital,lnt:Wpl██▇▅▅▅▅▄▁▁1459143414091309130913091309125911091109NANANA1019NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Ipl█▇▇▄▄▄▄▁▁▁914890887788785774777692683678NANANA617NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Wpl█▆▆▅▄▃▃▂▂▁910863849810804774771730725706NANANA645NANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:AssetsCurrent ▄▄█▆▃▂█▃▁▄▂▃▂▄▅▁▂▃▇▇▄▇▅▆▅▆▄▄▄▆▆▅▂▄▅▄▆▇9128751113102781578511248057259057518147498779587027688261087104391310439621010936101188089387099410289207808669478779771092NANANA
 us-gaap:AssetsCurrent dei:LegalEntity lnt:Ipl▄▃▇▃▂▃█▃▂▄▂▃▂▃▅▁▂▃▆▅▃▅▅▅▅▅▄▃▃▃▄▃▁▂▂▂435409621399355371715430330476357379330422534275338396601542418556527546497535449431417391467374289323341323NA428NANANA
 us-gaap:AssetsCurrent dei:LegalEntity lnt:Wpl▃▄▄█▃▂▂▁▂▃▂▂▁▃▂▂▃▃▄▄▄▄▂▂▂▂▂▂▂▄▄▃▂▂▂▁435442450593416384400351369418385382368416377380410423453454466457389401400402388395398468454433379386393367NA445NANANA
us-gaap:CashAndCashEquivalentsAtCarryingValue ▃▁▇▆▁▁█▁▁▂▁▁▁▁▃▁▁▁▅▂▄▃▁▁▁▁▁▁▂▂▂▂▂▁▂▃▅▆▅▆▅5516193170102023951927978884645139549756111614917115321413030114577126159137171140
 us-gaap:CashAndCashEquivalentsAtCarryingValue dei:LegalEntity lnt:Ipl▂▁▇▁▁▁█▁▁▁▁▁▁▁▃▁▁▁▄▁▁▁▁▁▁▁▁▁▁▁▁▁▂▁▁▂▁▁▁▂25918453923212344437723499225455465445223202135228NA
 us-gaap:CashAndCashEquivalentsAtCarryingValue dei:LegalEntity lnt:Wpl▂▁▁█▁▁▁▁▁▂▁▁▁▁▁▁▁▁▃▃▅▃▁▁▁▁▁▁▁▁▂▁▁▁▂▂▁▁▃▂22481633862323322453103548904626406280162222313103527NA
us-gaap:AccountsReceivableNetCurrent ▆▆▇▇▇▆█▇▅█▅▇▇██▅▆▆▇▅▆▇▁▁▁▁▁▁▁▁▁▁▁▃▃▂▂▂39640245142141735046541534348233642442449349131639039742729736142784851068178859894938192188198127140120NANANA
 us-gaap:AccountsReceivableNetCurrent dei:LegalEntity lnt:Ipl▆▆▇▇▆▄█▇▄█▄▅▅▇█▂▅▆▇▃▄▆▆▇▇▇▃▃▅▂▅▃▁▂▃▂2042022582312091532772371452641431941772402669718020023510415821620024225724613011516595183102517510883NA174NANANA
 us-gaap:AccountsReceivableNetCurrent dei:LegalEntity lnt:Wpl▆▆▆▆▇▆▆▅▆▇▆▇▇█▆▆▆▆▆▅▆▆▁▁▂▁▁▁▂▂▂▁▂▁▁▁1811901841801981901801701922121851932122261901851921851731661881857677987370748983847282768074NA84NANANA
us-gaap:InventoryRawMaterialsAndSupplies ▇▇█▇▇▇███▇▇▆▅▅▅▄▄▄▄▄▄▃▃▃▃▃▃▂▂▂▁▁▁▁▁▁▂▁10510010610510510110610910910599948886898383818382817272757269716864636161615861616461NANANA
 us-gaap:InventoryRawMaterialsAndSupplies dei:LegalEntity lnt:Ipl█▇█▇▇▇████▆▆▅▄▅▅▅▄▄▅▅▄▃▄▃▃▃▂▂▁▁▁▁▁▁▂605560585655596061605251484650484745464748424143403939373433333232313334NA33NANANA
 us-gaap:InventoryRawMaterialsAndSupplies dei:LegalEntity lnt:Wpl▇▇▇██▇███▇▇▆▅▅▄▃▄▄▄▃▃▂▂▃▂▂▂▂▂▂▁▁▂▁▁▁424343444542444544424339363635323433353231292930292829292928262627252626NA25NANANA
us-gaap:OtherAssetsCurrent ▃▂▃▃▃▂▃▂▂▂▂▂▂▂▂▂▂▂▄█▄▂▆▅▄▂▂▃▃▁▁▁▁▃▃▄▄▂1371011371511538012611385871011127095989864792174352271162942892098411912515743413460153132185192111NANANA
 us-gaap:OtherAssetsCurrent dei:LegalEntity lnt:Ipl▁▁▁▁▁▂▂▁▁▁▂▂▁▁▂▂▁▁▃█▄▂▅▅▃▂▂▂▂▁▁▁▁▂▁▁283022212143382923323936142737331328115308136651661681063438505424111126332122NA22NANANA
 us-gaap:OtherAssetsCurrent dei:LegalEntity lnt:Wpl▆▄▆█▇▁▄▅▄▁▅▄▃▁▄▄▄▁▇▄▆▂██▇▁▄▄▄▁▁▂▂▁▂▁8861861081032060715713646345205355512094518323113109921749576316202527162415NA9NANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:PropertyPlantAndEquipmentNet ██▇▇▇▇▆▆▆▆▅▅▅▅▄▄▄▄▄▃▃▃▃▃▃▃▂▂▂▂▂▂▁▁▁▁▁▁1368513527131311285412665124621200511695114391123410931106081044810279992098469626951993669173905089388763856684268326814180277913783873847248708170376937686668236730NANANA
 us-gaap:PropertyPlantAndEquipmentNet dei:LegalEntity lnt:Ipl██▇▇▇▇▆▆▅▅▅▄▄▄▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁▁▁758974807283708069476781643261936088592657645586550354355220512749934925480446874631455444334279419441364021396239033858379937423692367636323615NA3703NANANA
 us-gaap:PropertyPlantAndEquipmentNet dei:LegalEntity lnt:Wpl██▇▇▇▇▇▇▆▆▆▅▅▅▄▄▄▄▄▄▄▄▃▃▃▃▃▃▃▃▂▁▁▁▁▁569156385449537753225287518351184962491747824635452344264289422741414103409440283966393839013866381837813736368436333601314730913049302129842944NA2846NANANA
us-gaap:LongTermInvestments ██▇▇▇▇▆▆▆▅█▄▃▃▃▂▂▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁▁▁469467453443433431424420414396458354346337329324323346353349343344343338332329324321321319314308303300299296292289NANANA
us-gaap:OtherAssetsNoncurrent █▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁181272726872891038672692118142291010143538414355676885991111081059876829293121130137NANANA
 us-gaap:OtherAssetsNoncurrent dei:LegalEntity lnt:Ipl█▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁137931281919182016161488643445161512121826292921212019191719192149NA49NANANA
 us-gaap:OtherAssetsNoncurrent dei:LegalEntity lnt:Wpl█▁▁▁▁▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▂▂▂▂▂▂▂▂▂▁▂▂▂▂425231921246257432927252320176869202327293842385451635857533436444749NA57NANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:LiabilitiesCurrent ▅██▇▅▅▅▄██▅▃▃▃▄▄▄▄▂▂▂▃▆▆▄▄▂▃▂▂▂▂▁▁▁▁▁▂1650205420821949158716441548125720732149147012081165116213691373134813599909911023121417411733138414331052107210381020945957773855774760778866NANANA
 us-gaap:LiabilitiesCurrent dei:LegalEntity lnt:Ipl▇▇█▂▂▄▇▇▇▇▄▂▂▃▂▂▂▃▃▃▅▅▆▆▃▃▃▃▃▂▂▂▁▁▁▂835830882494484607798815798827603490493521487488484531551543644705771771507524517527520468490466414422389435NA482NANANA
 us-gaap:LiabilitiesCurrent dei:LegalEntity lnt:Wpl▇▇▅█▇▇▆▃▃▃▆▅▄▃▂▃▃▃▂▂▂▂▄▄▄▄▄▄▄▃▂▂▁▂▁▁700690508743677694601343352396589531420394303353343336295297314310459472431451419435422385287286250257216217NA292NANANA
us-gaap:LongTermDebtCurrent ▄▆▆▇▃▃▅▄██▂▁▁▁▄▄▄▄▁▁▂▂▅▅▄▄▁▁▁▁▁▁▁▁▁▁▁▁3576576567062562565063568558551055443143143133133331831834925093583584811111111111NANANA
 us-gaap:LongTermDebtCurrent dei:LegalEntity lnt:Ipl▄▄▄200200200NANA0250350350350100NANA0NANANA000150150150188383838NANA0NANANA0NANANANANANANA
 us-gaap:LongTermDebtCurrent dei:LegalEntity lnt:Wpl▁▁▁█▄▄▄150150150400250250250NANA0NANANA0NANANA00303030308888NANA0NANANA0NANANANANANANA
us-gaap:AccountsPayableCurrent ▄▅▇▅▄█▇▅▄▆▆▄▄▆▄▃▂▄▅▄▃▅▆▆▄▄▄▄▄▃▅▃▁▂▂▂▂▃375422497422387543498431363477478381369445365353323402438374356427471475388365368391368339418337263308314305300336NANANA
 us-gaap:AccountsPayableCurrent dei:LegalEntity lnt:Ipl▄▄▇▅▅█▇▄▃▅▅▃▂▄▃▃▂▄▆▅▄▆▇▆▅▄▄▅▄▃▅▃▂▁▁▁184207290216227304279203183220224163149186172160153197251222199259286262214187195213204163231171136118116119NA146NANANA
 us-gaap:AccountsPayableCurrent dei:LegalEntity lnt:Wpl▄▅▅▅▂▇▆▆▄██▅▅▇▃▄▃▄▃▂▂▃▃▅▃▃▃▃▃▃▄▂▁▂▁▂13615915115010418016217313420119715015719212213011113612298107112118152114120117124115126133106859893100NA118NANANA
us-gaap:OtherLiabilitiesCurrent ██▇▅▄▅▄▄▄▅▄▅▅▄▅▅▅▅▄▅▄▅▃▄▃▂▄▄▃▂▁▁▁▂▂▃▃▃407425389262249260255247251260217265272222273284304296250264232262204215191133223244196113999387127152161163160NANANA
 us-gaap:OtherLiabilitiesCurrent dei:LegalEntity lnt:Ipl█▆▆▃▅▂▅▅▄▃▃▆▄▂▃▆▆▂▄▅▄▃▂▄▂▂▄▄▄▁▁▁▁▁▁▁265207197871505617317012790921941315785182198691251481229068119617411313711436343131322628NA35NANANA
 us-gaap:OtherLiabilitiesCurrent dei:LegalEntity lnt:Wpl▇▄▆▆▆▂▅▅▅▂▆▆▇▂▅▆█▄▄▄▄▂▂▃▃▁▃▄▇▁▂▁▁▁▁▁1287411310911248959589511081121235491120146798682824654606436597212632383334322933NA38NANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis us-gaap:CarryingReportedAmountFairValueDisclosure████▆▆▇▆▄▃▂▂▂▂▁619161906191614456185502575454834912486643604359432043204130NANA3835NANANANA32923338333933363153314231233138NANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,dei:LegalEntity us-gaap:CarryingReportedAmountFairValueDisclosure,lnt:Ipl███▁3147314731462850NA2552NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,dei:LegalEntity us-gaap:CarryingReportedAmountFairValueDisclosure,lnt:Wpl▁▁▁█1933193219322181NA1834NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LongTermDebtNoncurrent █▇▇▇▇▇▇▆▄▄▄▅▅▅▃▃▃▃▄▃▃▃▁▁▂▂▂▂▂▂▁▁▁▁▁▁▁▁58335533553554385362524652485127405640104255435443164315381635883522352238553717360636062799282929802977310431413121313628282752272827032703270327032703NANANA
 us-gaap:LongTermDebtNoncurrent dei:LegalEntity lnt:Ipl████▇▆▆▅▄▄▄▅▅▅▅▄▃▃▃▃▂▂▁▁▂▂▁▁▁▁▁▁▁▁▁▁294729472946285026672552255121812102205620952194215421532153192418571856186817301618161813701370152015201336136413441359135913591334130913081308NA1308NANANA
 us-gaap:LongTermDebtNoncurrent dei:LegalEntity lnt:Wpl████▆▆▆███▅▅▅▅▅▅▅▅▅▅▅▅▃▃▃▃▃▃▃▃▁▁▁▁▁▁178317821782178115851584158418341833183315361535153515351534153415341533154315431543154312931323132313231323133113311331108210821082108210821082NA1081NANANA
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent ▇▇▇███████▇▇▇█▇▇▇▇▆▆▆▆▁▁▁▁▅▅▅▅▃▃▃▄▂▂▃▃452484476487493509487488488504481482481489455452446451416417417421201202203206356359360364310309309312235241299303NANANA
 us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent dei:LegalEntity lnt:Ipl▇▇▇███▇███████▇▇▇▇▆▆▆▆▁▁▁▁▅▅▅▅▄▄▄▄▂▂16116716517117417816817017117317117117217316116016016014114114214246474748120121122122991001001017274NA110NANANA
 us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent dei:LegalEntity lnt:Wpl▇█▇███▇███▇▇▇▇▆▆▆▆▆▆▆▆▁▁▁▁▅▅▅▅▃▃▃▃▂▂20321020321021421720720921021320420520520718618618618817817917918084858788156158159159127127127128103103NA119NANANA
us-gaap:OtherLiabilitiesNoncurrent ▅▄▄▇█▃▃▄▄▄▄▃▄▃▄▄▄▄▅▅▃▃▃▂▃▃▃▃▂▃▃▂▂▃▂▁▁▁349298305413442287286310313306296288297279300297310306333342259260267253262273271275257262269245248259251212208208NANANA
 us-gaap:OtherLiabilitiesNoncurrent dei:LegalEntity lnt:Ipl▅▄▄██▃▃▄▄▄▄▄▃▃▄▄▄▄▄▄▂▂▂▂▂▂▂▂▂▂▂▂▂▃▂▁269253251360365220221242239242238228221214229227223229231243177185182174171169181183178182189186188199187143NA141NANANA
 us-gaap:OtherLiabilitiesNoncurrent dei:LegalEntity lnt:Wpl▅▆▅▅█▇▇▆▆▆▅▅▆▅▅▅▆▅▇▇▅▄▃▂▃▄▄▄▃▃▄▂▂▂▁▂162168164159188178175174172167162163168159162157169162181177159155138133142153153155141144148135135136124132NA135NANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:StockholdersEquity █▇▇▆▆▆▅▅▅▄▄▄▄▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁55025205496946994682458545704350423141824154405038963862385937903764372437453620359734383435333733313281326631603145313431163014299730133001292729202893NANANA
 us-gaap:StockholdersEquity dei:LegalEntity lnt:Ipl██▇▇▇▇▆▆▅▅▅▅▄▄▄▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁339532713244314531423030283826542514250924322351224722492137203620421995199119081826181418291731171816791663155515351519149813951360139413631294NA1389NANANA
 us-gaap:StockholdersEquity dei:LegalEntity lnt:Wpl██▇▆▆▆▆▅▄▄▄▃▃▃▄▄▃▃▃▃▃▃▃▃▃▃▃▂▂▂▂▁▁▁▁▁243623632324218521792149214620551900188118091751174417301813177817691756175917231716170317041672166716421633160115951583148014521445144214291406NA1369NANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:AdditionalPaidInCapital█▆▄▃▃▃▃▂▁▁2674244522362108210020452038194718511845NANANA1693NANANA1663NANANA1509NANANA1507NANANA1511NANANA1510NANANA1506NANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents us-gaap:RetainedEarnings█▇▇▅▄▄▄▂▂▁2833276527392597258725452539241223892346NANANA2177NANANA2068NANANA1938NANANA1780NANANA1630NANANA1510NANANA1394NANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:AdditionalPaidInCapital,lnt:Ipl█▇▇▇▇▆▃▂▁▁2447234723222322232222222027192717971797NANANA1597NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:AdditionalPaidInCapital,lnt:Wpl██▇▅▅▅▅▄▁▁1459143414091309130913091309125911091109NANANA1019NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Ipl█▇▇▄▄▄▄▁▁▁914890887788785774777692683678NANANA617NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Wpl█▆▆▅▄▃▃▂▂▁910863849810804774771730725706NANANA645NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:CommonStockValue ████████████████▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁22222222222222221111111111111111111111NANANA
us-gaap:RetainedEarningsAccumulatedDeficit ███▇▇▇▇▆▆▆▆▅▅▅▅▅▄▄▄▄▄▄▄▃▃▃▃▂▂▂▂▂▁▂▂▁▁▁28332765273925972587254525392412238923462324222822052177218121162098206820971979197319381934183718321780176716611648163016121511149515101500142514211394NANANA
 us-gaap:RetainedEarningsAccumulatedDeficit dei:LegalEntity lnt:Ipl███▆▆▆▆▅▅▅▅▄▄▄▄▃▄▃▄▃▃▃▃▃▃▃▃▂▂▂▂▁▂▂▂▁914890887788785774777692683678701619615617631555561554614532550537552485501493507429439448456384398433456358NA382NANANA
 us-gaap:RetainedEarningsAccumulatedDeficit dei:LegalEntity lnt:Wpl█▇▇▆▆▆▆▅▅▅▄▄▄▄▆▅▅▅▅▅▅▄▄▄▄▃▃▃▃▂▂▂▂▂▁▁910863849810804774771730725706684666659645788753743731734698691678679647642617608575570557545517510507494471NA459NANANA
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax █▆▆▆█▆▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▃▁▁211121000000000000000000000000000000-1-1NANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▄▄▅▄▅▄█▁▄▄▇▄▆▅▄▆▅▄▅▅▆▄▆▄▆1601512329518185507-15489100381168333205144281228175178202314127315154293NANANA198NANANA215NANANA261NANANA189
 us-gaap:NetCashProvidedByUsedInOperatingActivities dei:LegalEntity lnt:Ipl▄▄▄▄▅▃█▁▃▄▆▅▆▅▄▆▅▅▄▅▆▄▆▅▅2534491276-43365-261-65-3020291176105-15155116672312417032167100105NANANA65NANANA78NANANA128NANANANA
 us-gaap:NetCashProvidedByUsedInOperatingActivities dei:LegalEntity lnt:Wpl▆▁▆▃▄▄▄▂▆▃▅▂▆▂█▅▅▂▆▂▆▁▅▄▅1486315186122111119841411041318414582187127123731457215758130106128NANANA105NANANA94NANANA173NANANANA
us-gaap:NetCashProvidedByUsedInInvestingActivities ▇▄▆▆▄▆▁██▄▃▅▅▄▆▆▆▅▇▆▆▆▆▇▇-179-426-254-242-364-251-637-93-85-424-445-322-303-414-271-280-220-306-142-219-250-277-271-192-176NANANA-119NANANA-135NANANA-233NANANA-232
us-gaap:NetCashProvidedByUsedInFinancingActivities ▄▄▃▇▅▂█▆▃█▄▅▂▅▆▃▃▃▃▂▂▆▂▃▁609347302176-56365231-934266153-291322050-9-349-26-23195-4939-112NANANA-46NANANA-60NANANA-61NANANA7
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity lnt:Ipl▃▂▆▄▅▁█▅▂▆▂▄▂▄▆▂▂▃▄▂▂▅▂▂▂43-27259119139-793541558242-1477-3978234125301083-1614411-1-7NANANA18NANANA4NANANA-20NANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▄▄▅▄▅▄█▁▄▄▇▄▆▅▄▆▅▄▅▅▆▄▆▄▆1601512329518185507-15489100381168333205144281228175178202314127315154293NANANA198NANANA215NANANA261NANANA189
 us-gaap:NetCashProvidedByUsedInOperatingActivities dei:LegalEntity lnt:Ipl▄▄▄▄▅▃█▁▃▄▆▅▆▅▄▆▅▅▄▅▆▄▆▅▅2534491276-43365-261-65-3020291176105-15155116672312417032167100105NANANA65NANANA78NANANA128NANANANA
 us-gaap:NetCashProvidedByUsedInOperatingActivities dei:LegalEntity lnt:Wpl▆▁▆▃▄▄▄▂▆▃▅▂▆▂█▅▅▂▆▂▆▁▅▄▅1486315186122111119841411041318414582187127123731457215758130106128NANANA105NANANA94NANANA173NANANANA
us-gaap:NetIncomeLoss ▆▄█▃▄▃▇▃▄▃▆▃▃▂▄▃▃▁▆▂▃▂▅▂▄172114228971278720810212396171961036513186993618270996215564110NA1606780NA1546938NA1255579NA1535248
 us-gaap:NetIncomeLoss dei:LegalEntity lnt:Ipl▅▃█▃▄▃▇▄▃▂▇▃▃▂▇▃▃▁▇▂▃▂▆▂▃▂▆▂▃▂▆▂▁▁▆▁▂▂▆▂▁85471434755411295449181234539261163448812019502210520462111224312510619-1910112711100219
 us-gaap:NetIncomeLoss dei:LegalEntity lnt:Wpl█▄▆▃▅▃▇▃▄▄▄▃▃▂▆▃▃▁▆▃▃▂▅▂▄▃▅▂▃▃▄▂▂▃▄▁▃▂▄▂▂8949754265387639545349384532694347246739442961345438613443415636314251254435503037
 us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents,dei:LegalEntity us-gaap:RetainedEarnings,lnt:Wpl89NANANA65NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:DepreciationDepletionAndAmortization █▇▇▆▄▁▁146143143142136130129NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DepreciationDepletionAndAmortization dei:LegalEntity lnt:Ipl█▇▇▆▃▂▁85838382777473NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DepreciationDepletionAndAmortization dei:LegalEntity lnt:Wpl██▇█▇▂▁59595859585554NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet ▅▃▆▆▄▄▇▄▆▃▄▆▄▄▄█▃▅▆▃▅▁▇▃▅10-404427-22-975-1035-55-339-18-11-1789-44-132-315-9571-360NANANA3NANANA13NANANA-22NANANA31
 us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet dei:LegalEntity lnt:Ipl▆▅▅▆▂▅▇▅▅▅▄▆▃▄▇█▃▄▄▅▄▁▆▁▇18118-43430272-1011-21-122439-20-17-9-4-12-5018-4728NANANA-19NANANA6NANANA-20NANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ▇▄▆▆▄▆▁██▄▃▅▅▄▆▆▆▅▇▆▆▆▆▇▇-179-426-254-242-364-251-637-93-85-424-445-322-303-414-271-280-220-306-142-219-250-277-271-192-176NANANA-119NANANA-135NANANA-233NANANA-232
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▁█▂▁▃▆▃277636351278374553380NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:PaymentsToAcquirePropertyPlantAndEquipment dei:LegalEntity lnt:Ipl165NA246188261NA244NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:PaymentsToAcquirePropertyPlantAndEquipment dei:LegalEntity lnt:Wpl112NA10490112NA136NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▄▄▃▇▅▂█▆▃█▄▅▂▅▆▃▃▃▃▂▂▆▂▃▁609347302176-56365231-934266153-291322050-9-349-26-23195-4939-112NANANA-46NANANA-60NANANA-61NANANA7
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity lnt:Ipl▃▂▆▄▅▁█▅▂▆▂▄▂▄▆▂▂▃▄▂▂▅▂▂▂43-27259119139-793541558242-1477-3978234125301083-1614411-1-7NANANA18NANANA4NANANA-20NANANANA
us-gaap:ProceedsFromIssuanceOfLongTermDebt ▄▁▄█▁▁▆300030065000500NANA5500NANA500NANANA0NANANA810NANANANANANANANANANANANANANANANANANANA
us-gaap:RepaymentsOfLongTermDebt █▁▇▁▁▇▃300325030252100NANA20NANA3110NANA130NANA31046NANA0NANANANANANANANANANANANANANANA
 us-gaap:RepaymentsOfLongTermDebt us-gaap:DebtInstrument,us-gaap:LongtermDebtType,dei:LegalEntity lnt:TermLoanCreditAgreementThroughAprilTwoThousandandTwenty,lnt:TermLoanCreditAgreement,lnt:AlliantEnergyFinanceLLC300NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:RepaymentsOfLongTermDebt █▁▇▁▁▇▃300325030252100NANA20NANA3110NANA130NANA31046NANA0NANANANANANANANANANANANANANANA
 us-gaap:RepaymentsOfLongTermDebt us-gaap:DebtInstrument,us-gaap:LongtermDebtType,dei:LegalEntity lnt:TermLoanCreditAgreementThroughAprilTwoThousandandTwenty,lnt:TermLoanCreditAgreement,lnt:AlliantEnergyFinanceLLC300NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value222222222222222211111111111111111111111
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Par Or Stated Value Per Share

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value249245240237237236235233231231231231227227227227113113113113112110110110110110110110110110110110110111110110110110110110
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Common Stock Shares Authorized

us-gaap:CommonStockSharesAuthorized



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-04-202016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value480480480480480480480480480480480480480480480480240240240240240240240240240240240240240240240240240240240240240240240240
Percentage of CommonStockSharesAuthorized100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value244239238236235232231110110110110110110110110110110110110
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value244239237236235232231110110110110110110110110110110110110
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

Earnings Per Share Diluted

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 End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value9158809907909878739288169168569067658537979247548437408987178978048437509528328667188597508876907658791021819945832951741890
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value518496596441555494547474525472527420450434516411458398504382489431476411528463494383477393497360398404484374477417534389454
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax56.756.460.255.856.256.659.058.257.455.258.254.952.854.555.854.554.453.956.153.354.553.656.554.955.555.657.153.455.652.456.152.352.146.047.445.650.550.156.252.551.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax56.756.460.255.856.256.659.058.257.455.258.254.952.854.555.854.554.453.956.153.354.553.656.554.955.555.657.153.455.652.456.152.352.146.047.445.650.550.156.252.551.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value375362372326415369370330381374370334393352397334375330382324397359354324410355360319369345376315354344374326388348369312392
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax41.041.237.641.342.142.339.940.541.743.840.843.746.044.242.944.344.544.742.645.344.344.742.043.243.142.741.644.643.046.042.445.746.339.236.739.941.141.838.842.244.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax41.041.237.641.342.142.339.940.541.743.840.843.746.044.242.944.344.544.742.645.344.344.742.043.243.142.741.644.643.046.042.445.746.339.236.739.941.141.838.842.244.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:MajorCustomers, us-gaap:StatementBusinessSegments

lnt:RetailCommercial, lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value182230171181173215172174173205165165
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax19.923.321.718.319.923.221.119.020.222.721.719.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax19.923.321.718.319.923.221.119.020.222.721.719.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailCommercial lnt:Electric100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:RetailCommercial, lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value451016634511195741121849
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.01.02.06.45.21.22.46.24.91.42.45.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.01.02.06.45.21.22.46.24.91.42.45.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailCommercial lnt:Gas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:RetailIndustrial, lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value209263214208213247225201206243207195
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax22.926.627.121.124.526.727.622.024.226.827.222.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax22.926.627.121.124.526.727.622.024.226.827.222.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailIndustrial lnt:Electric100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:RetailIndustrial, lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value422533256324
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.50.20.30.50.40.30.30.60.70.30.30.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.50.20.30.50.40.30.30.60.70.30.30.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailIndustrial lnt:Gas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:RetailResidential, lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value266331233274242312248259239296229241
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax29.133.529.527.827.833.730.428.328.032.730.028.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax29.133.529.527.827.833.730.428.328.032.730.028.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailResidential lnt:Electric100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:RetailResidential, lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value90203513184213711079213389
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.92.14.513.49.72.34.612.19.32.44.410.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.92.14.513.49.72.34.612.19.32.44.410.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailResidential lnt:Gas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Steam, lnt:OtherUtility



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
Value101099888899888
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.11.20.91.20.91.00.91.01.01.10.91.11.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.11.20.91.20.91.00.91.01.01.10.91.11.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Steam lnt:OtherUtility100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:TransportationandOther, us-gaap:AllOtherSegments



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value212122161010891010
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.42.22.91.71.11.31.01.01.31.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.42.22.91.71.11.31.01.01.31.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:TransportationandOther us-gaap:AllOtherSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Wholesale, lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value404941464150435352635963
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.55.05.24.74.85.45.35.96.17.07.87.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.55.05.24.74.85.45.35.96.17.07.87.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wholesale lnt:Electric100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value304031323537
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.34.14.03.33.84.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.34.14.03.33.84.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:Electric100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value118111599
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.30.91.51.51.01.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.30.91.51.51.01.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:Gas100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:OtherUtility



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value12212332
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.20.30.20.20.30.40.40.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.20.30.20.20.30.40.40.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:OtherUtility100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:MajorCustomers, us-gaap:StatementBusinessSegments, dei:LegalEntity

lnt:RetailCommercial, lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value119158111116146114
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.116.014.111.815.714.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.116.014.111.815.714.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailCommercial lnt:Electric lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:RetailCommercial, lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value627259646958
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.87.37.66.57.57.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.87.37.66.57.57.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailCommercial lnt:Electric lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:RetailCommercial, lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value245834611
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.60.61.13.50.71.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.60.61.13.50.71.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailCommercial lnt:Gas lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:RetailCommercial, lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value21472847
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.40.40.92.90.50.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.40.40.92.90.50.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailCommercial lnt:Gas lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:RetailIndustrial, lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value121157118116141128
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.215.915.011.815.215.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.215.915.011.815.215.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailIndustrial lnt:Electric lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:RetailIndustrial, lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value88105959210696
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.710.712.19.411.511.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.710.712.19.411.511.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailIndustrial lnt:Electric lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:RetailIndustrial, lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value211321
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.30.20.20.30.20.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.30.20.20.30.20.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailIndustrial lnt:Gas lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:RetailIndustrial, lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value100211
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.20.00.10.20.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.20.00.10.20.10.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailIndustrial lnt:Gas lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:RetailResidential, lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value147196125147180139
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.119.815.914.919.417.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.119.815.914.919.417.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailResidential lnt:Electric lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:RetailResidential, lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value119135107127132109
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.013.713.612.914.313.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.013.713.612.914.313.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailResidential lnt:Electric lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:RetailResidential, lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value481120771222
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.31.22.57.91.42.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax5.31.22.57.91.42.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailResidential lnt:Gas lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:RetailResidential, lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value4181553914
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.60.91.95.51.01.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.60.91.95.51.01.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:RetailResidential lnt:Gas lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:Steam, lnt:OtherUtility, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value1010998888
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.11.20.91.20.91.00.91.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.11.20.91.20.91.00.91.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Steam lnt:OtherUtility lnt:Ipl100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Wholesale, lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value141714161813
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.61.81.81.72.01.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.61.81.81.72.01.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wholesale lnt:Electric lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:Wholesale, lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value263226293129
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.93.23.33.03.43.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.93.23.33.03.43.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wholesale lnt:Electric lnt:Wpl100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value223122222325
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.43.22.82.32.53.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.43.22.82.32.53.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:Electric lnt:Ipl100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value88991111
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.90.91.21.01.21.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.90.91.21.01.21.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:Electric lnt:Wpl100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value758856
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.90.51.00.90.60.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.90.51.00.90.60.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:Gas lnt:Ipl100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value433632
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.40.50.60.40.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.40.40.50.60.40.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:Gas lnt:Wpl100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:OtherUtility, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value11112232
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.20.20.20.20.20.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.20.20.20.20.20.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:OtherUtility lnt:Ipl100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherCustomer, lnt:OtherUtility, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value01000100
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.10.00.10.00.10.10.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.10.00.10.00.10.10.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:OtherCustomer lnt:OtherUtility lnt:Wpl100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments

lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value730915691743704861726708695840680677666864675668623835640671622771643675798612633815612572796620842
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax79.892.587.575.380.692.789.077.381.392.789.079.483.693.589.679.384.293.089.374.877.491.585.870.992.185.373.791.988.774.878.065.688.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax79.892.587.575.380.692.789.077.381.392.789.079.483.693.589.679.384.293.089.374.877.491.585.870.992.185.373.791.988.774.878.065.688.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Electric100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value15241652151474468185138456215410639571529338511981524776240397319746501674622946
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.64.28.321.916.94.88.420.316.15.18.218.113.44.37.618.012.64.27.222.119.05.610.225.34.610.223.05.37.221.84.524.24.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.64.28.321.916.94.88.420.316.15.18.218.113.44.37.618.012.64.27.222.119.05.610.225.34.610.223.05.37.221.84.524.24.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Gas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:OtherUtility



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value1113111011111210131311111113912131313141615121522171717121313151615
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.31.51.11.41.11.41.31.31.41.51.21.51.41.71.01.61.61.81.52.11.81.91.42.12.42.02.52.01.42.01.81.51.81.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.31.51.11.41.11.41.31.31.41.51.21.51.41.71.01.61.61.81.52.11.81.91.42.12.42.02.52.01.42.01.81.51.81.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:OtherUtility100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AllOtherSegments



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
Value21212122161010108991010
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.42.42.22.91.71.11.11.31.01.11.01.31.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.42.42.22.91.71.11.11.31.01.11.01.31.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:AllOtherSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementBusinessSegments, dei:LegalEntity

lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value424560392419509422
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax46.456.649.642.554.851.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax46.456.649.642.554.851.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Electric lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value305355298323352304
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax33.435.937.832.837.937.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax33.435.937.832.837.937.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Electric lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value8324381242642
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.12.54.912.62.95.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.12.54.912.62.95.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Gas lnt:Ipl100.0100.0100.0100.0100.0100.0

lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value691626911826
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.61.73.49.21.93.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.61.73.49.21.93.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Gas lnt:Wpl100.0100.0100.0100.0100.0100.0

lnt:OtherUtility, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value1112101010101110
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.41.11.31.11.21.31.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.21.41.11.31.11.21.31.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:OtherUtility lnt:Ipl100.0100.0100.0100.0100.0100.0100.0100.0

lnt:OtherUtility, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value01000100
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.10.00.10.00.10.10.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.10.10.00.10.00.10.10.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:OtherUtility lnt:Wpl100.0100.0100.0100.0100.0100.0100.0100.0

Revenues

us-gaap:Revenues



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value9158809907909878739288169168569067658537979247548437408987178978048437509528328667188597508876907658791021819945832951741890
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Cost Of Goods And Services Sold

us-gaap:CostOfGoodsAndServicesSold



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value122118127112123120129119
Percentage of CostOfGoodsAndServicesSold100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax13.313.512.914.212.513.813.914.7

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value8483917787849284
Percentage of CostOfGoodsAndServicesSold69.170.372.068.971.370.571.970.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.29.59.39.88.99.710.010.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl16.316.815.417.515.817.216.917.8

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value3735353535353635
Percentage of CostOfGoodsAndServicesSold30.929.728.031.128.729.528.129.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.14.03.64.43.64.13.94.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl10.09.79.610.78.59.69.810.7

Costs And Expenses

us-gaap:CostsAndExpenses



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value727719700640810752672664750726675616711697762626697660663608744712648647798665614738673581670836747817705640781
Percentage of CostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax79.481.770.781.082.186.172.481.581.984.874.580.583.387.582.483.082.789.373.884.883.088.676.986.283.876.885.686.075.984.287.581.991.286.574.186.487.8

dei:LegalEntity

lnt:Ipl



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
Value422415423366481439404397450423395353400399390363396373387348423407382377471394348436385325374368355430379344
Percentage of CostsAndExpenses58.057.860.457.359.458.560.159.760.058.258.657.556.457.351.258.056.856.558.557.356.957.159.058.459.059.356.759.157.255.955.944.047.652.753.853.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax46.147.242.746.448.850.343.648.749.149.443.646.246.950.142.248.147.050.443.148.647.250.745.350.449.545.548.650.843.547.148.936.043.445.539.846.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl81.483.670.983.186.889.073.983.685.689.675.084.289.092.075.688.386.593.676.891.286.694.580.391.789.179.890.991.477.590.294.076.095.190.170.988.4

lnt:Wpl



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
Value281288263259317308266267297301279261307294282259296281272256316300260264322265260297283254289287281313282260
Percentage of CostsAndExpenses38.740.137.740.539.141.039.640.239.741.641.442.443.242.237.041.442.542.641.142.242.542.140.240.940.439.842.340.242.043.743.334.437.638.440.140.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax30.732.826.632.832.135.328.732.832.535.330.834.136.036.930.534.435.238.030.335.835.237.430.935.333.930.636.234.631.936.837.928.234.333.229.735.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl75.079.670.979.576.483.471.980.878.080.675.578.078.183.571.077.679.085.171.279.079.783.573.581.578.673.481.380.375.280.581.876.886.180.776.583.3

Operating Income Loss

us-gaap:OperatingIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value18816029014917612125615116512923114914299162128145792351091529119410315410820110312010121310895931857212799246100109
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax20.618.329.319.017.913.927.618.518.115.225.519.516.712.517.617.017.310.726.215.217.011.423.113.816.213.023.214.414.013.524.115.812.510.618.18.813.512.025.913.612.2

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value9681173747354143777549131664934125486225117336523933457361003441291123523261161847221554538
Percentage of OperatingIncomeLoss51.450.559.849.741.644.855.951.445.637.956.944.434.734.977.437.342.532.349.631.042.826.148.232.937.333.349.733.634.128.552.432.525.028.162.925.736.922.763.144.935.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.69.217.59.47.46.215.49.58.35.714.58.75.84.413.66.47.33.513.04.77.33.011.14.56.04.311.54.84.83.912.65.13.13.011.42.35.02.716.46.14.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl18.616.429.116.913.211.026.116.414.410.425.015.811.08.024.411.713.56.423.28.813.45.519.78.310.97.820.29.18.67.422.59.86.06.524.04.99.95.429.111.68.4

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value93731086798611046384729073865811575784911068805993608767955972659361647386457470865269
Percentage of OperatingIncomeLoss49.845.937.344.755.550.540.741.950.756.139.249.460.258.370.758.354.062.246.862.752.865.148.258.156.962.447.657.860.264.343.756.567.678.346.963.258.570.235.251.963.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax10.28.410.98.59.97.011.27.89.28.510.09.610.17.312.49.99.36.712.39.59.07.411.18.09.28.111.18.38.58.710.58.98.48.38.55.67.98.49.17.17.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl25.020.429.120.523.616.628.119.222.019.424.522.021.916.529.022.421.014.928.821.020.316.526.518.521.419.126.618.719.718.924.819.518.221.223.213.919.320.123.516.717.7

us-gaap:PublicUtilityRegulatedOrUnregulatedStatus, us-gaap:StatementBusinessSegments

us-gaap:UnregulatedOperation, us-gaap:AllOtherSegments



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-03-31
Value-28858106997-785586679958681175
Percentage of OperatingIncomeLoss-1.22.95.52.93.46.73.73.96.25.1-48.24.43.53.66.34.33.69.05.82.78.55.73.910.97.44.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.20.81.10.50.91.20.71.01.20.9-8.50.70.61.01.00.70.81.20.90.61.20.80.91.70.90.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:UnregulatedOperation us-gaap:AllOtherSegments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments

lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value14628313212610024813412611123213510798244119109752321001046819089941998573203915920689241
Percentage of OperatingIncomeLoss77.697.888.771.582.497.189.276.585.7100.590.875.098.7150.292.875.395.698.792.668.574.797.986.361.299.183.261.095.084.461.8111.369.997.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.028.716.812.811.426.816.513.813.025.617.712.612.426.415.813.010.225.914.111.78.522.611.99.923.012.08.622.913.37.720.29.425.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Electric20.031.019.217.014.228.918.617.916.027.719.915.814.828.317.716.412.227.915.815.611.024.713.814.025.014.011.624.915.010.325.914.428.6

lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value41-474518-253115-23283-31286-5-23612-4243-35370327-235-2
Percentage of OperatingIncomeLoss22.1-1.64.825.615.1-0.83.619.012.2-1.02.619.63.7-2.31.519.77.6-2.4-1.823.713.7-2.32.627.9-1.75.430.90.43.329.0-1.528.1-1.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.5-0.50.94.62.1-0.20.73.41.8-0.30.53.30.5-0.40.33.40.8-0.6-0.34.01.6-0.50.44.5-0.40.84.30.10.53.6-0.33.8-0.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Gas27.3-11.311.020.912.4-4.57.917.011.4-5.26.218.13.5-9.43.318.96.4-15.0-3.918.38.2-9.33.517.9-8.57.618.91.77.216.6-6.015.7-6.2

lnt:OtherUtility



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value2-2210-2001-4-700-9012-603521270221110-34
Percentage of OperatingIncomeLoss1.4-1.81.00.90.0-2.10.20.60.8-3.8-3.30.30.3-9.20.21.41.5-8.60.12.93.52.70.72.15.1-0.12.82.40.71.41.80.1-2.61.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.3-0.30.30.20.0-0.30.10.10.2-0.6-0.80.10.0-1.20.00.20.3-0.90.00.40.60.30.20.30.8-0.00.40.30.20.20.20.0-0.30.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:OtherUtility23.3-21.825.012.80.0-22.04.98.410.6-37.4-68.84.33.4-67.64.314.516.7-51.11.521.632.316.111.514.134.6-1.716.316.912.310.912.40.6-19.826.4

lnt:UtilityBusiness



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value19015528114117111524714115912222214013593240123140742271021468318794145195941132059688203121242
Percentage of OperatingIncomeLoss101.296.497.194.597.195.396.693.396.394.196.193.894.993.2148.295.696.594.696.493.795.791.196.491.094.297.391.594.396.189.192.6109.995.498.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax20.817.628.517.917.413.226.617.317.414.324.518.315.911.726.116.316.710.125.314.216.310.322.312.515.222.613.113.223.114.011.619.912.925.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:UtilityBusiness0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments, dei:LegalEntity

lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value67175684614473
Percentage of OperatingIncomeLoss35.660.346.026.556.548.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.317.78.74.715.69.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Electric lnt:Ipl15.831.217.611.128.417.4

lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value79108647910461
Percentage of OperatingIncomeLoss42.137.442.745.040.640.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.611.08.18.111.27.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Electric lnt:Wpl25.930.621.424.629.520.2

lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value27-4426-32
Percentage of OperatingIncomeLoss14.5-1.42.814.9-1.21.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.0-0.40.52.7-0.30.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Gas lnt:Ipl32.9-16.910.921.1-11.65.9

lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value14031812
Percentage of OperatingIncomeLoss7.6-0.22.010.70.41.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax1.6-0.10.41.90.10.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Gas lnt:Wpl20.7-3.011.220.76.111.0

lnt:OtherUtility, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value20210011
Percentage of OperatingIncomeLoss1.3-0.10.90.90.2-0.10.61.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.3-0.00.30.20.0-0.00.20.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:OtherUtility lnt:Ipl21.6-1.624.113.33.7-0.912.816.2

lnt:OtherUtility, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0-2000-200
Percentage of OperatingIncomeLoss0.2-1.70.10.0-0.2-2.1-0.4-0.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.0-0.30.00.0-0.0-0.3-0.1-0.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:OtherUtility lnt:Wpl60.0-245.550.00.0-100.0-250.0-150.0-400.0

Interest Expense

us-gaap:InterestExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value68696869666363615956535252514848484746464645444545424242383838384040413940
Percentage of InterestExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.57.96.98.86.77.26.87.56.56.65.96.96.16.45.36.45.76.45.26.55.25.75.36.04.74.95.95.04.35.65.13.84.94.34.45.34.6

dei:LegalEntity

lnt:Ipl



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
Value343431312928303029282727272725252425232324222122221919191919191919192120
Percentage of InterestExpense50.149.646.445.544.345.648.049.650.351.151.852.853.054.152.352.151.952.551.351.451.750.149.150.149.846.146.446.050.950.850.650.449.049.051.151.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax3.83.93.24.03.03.33.33.73.33.43.13.63.23.52.83.33.03.42.63.32.72.82.63.02.42.32.72.32.22.82.61.92.42.12.22.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl6.66.95.37.15.35.85.66.45.76.15.36.66.16.44.96.15.46.34.76.34.95.34.65.54.34.05.14.13.95.44.94.05.34.24.05.2

lnt:Wpl



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
Value252425262524242424242323222222222222232323232121212121211919201920202018
Percentage of InterestExpense36.436.037.237.738.938.438.240.141.743.642.943.843.844.246.947.747.748.149.850.149.650.847.146.846.749.950.150.051.451.651.451.449.549.547.747.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.72.82.63.32.62.82.63.02.72.92.53.02.72.82.53.02.73.12.63.22.62.92.52.82.22.43.02.52.22.92.61.92.42.12.12.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl6.76.96.88.06.26.66.57.46.56.66.26.95.86.45.86.96.16.96.07.25.86.45.96.55.15.96.75.85.26.35.65.36.15.25.46.0

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value-1-3-3-3-4-1-1-2-20000000000000001000001000000
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.2-0.4-0.4-0.4-0.4-0.2-0.2-0.2-0.30.00.00.00.00.00.00.00.00.00.00.00.00.00.0-0.00.20.10.00.10.10.10.10.10.10.10.1-0.10.1

dei:LegalEntity

lnt:Ipl



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
Value0-1-2-1-10000000000000000-200000000000000
Percentage of OtherNonoperatingIncomeExpense47.444.154.145.547.537.531.235.033.30.050.0200.0-100.0100.00.00.00.066.7-100.00.0100.00.00.0-100.00.00.033.312.50.00.018.2-14.30.025.033.360.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.1-0.2-0.2-0.2-0.2-0.1-0.1-0.1-0.10.00.00.0-0.00.00.00.00.00.0-0.00.00.0-0.30.00.00.00.00.00.00.00.00.0-0.00.00.00.0-0.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl-0.2-0.3-0.3-0.3-0.3-0.1-0.1-0.1-0.20.00.00.0-0.00.00.00.00.00.1-0.00.00.0-0.60.00.00.00.00.00.00.00.00.1-0.00.00.00.0-0.1

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-06-302012-03-312011-06-302010-09-302010-06-30
Value0-1-1-1-1-1-1-1-10000000000000000000000000
Percentage of OtherNonoperatingIncomeExpense26.341.237.848.540.0106.281.250.045.8-100.050.00.0100.00.0-100.00.050.033.3300.050.0-100.00.0-250.0300.00.00.00.0-33.312.5-16.79.10.0-16.7-20.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.1-0.2-0.1-0.2-0.2-0.2-0.1-0.1-0.1-0.00.00.00.00.0-0.00.00.00.00.00.0-0.00.1-0.1-0.00.00.00.0-0.00.0-0.00.00.0-0.00.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-0.1-0.4-0.4-0.5-0.4-0.5-0.4-0.3-0.3-0.00.00.00.00.0-0.00.10.00.00.10.0-0.00.3-0.1-0.10.00.00.0-0.00.0-0.00.00.0-0.00.0

Income Loss From Continuing Operations

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

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value153133251108142932191161409819711811977138105121482108211960170771311797895192867116043100219
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.815.125.413.714.510.723.714.315.311.521.815.414.09.715.013.914.46.623.411.513.37.620.210.413.820.711.011.121.712.59.315.75.310.623.1

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value716015049583812356522610844362311435479100164657817418619259417598028135
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest46.245.359.845.640.641.656.148.537.327.155.037.930.329.782.233.538.920.047.720.139.19.546.222.531.248.125.126.749.220.38.361.40.728.661.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax7.86.915.26.35.94.513.36.95.73.112.05.84.22.912.44.75.61.311.22.35.20.79.32.34.39.92.83.010.72.50.89.60.03.014.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl13.712.225.211.210.47.922.511.910.05.620.610.68.05.322.18.610.32.419.94.39.61.316.54.27.817.45.25.319.04.91.520.30.16.025.4

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value815992498046864665557254654810364693410158664785528188516487555778366579
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest52.944.836.845.956.249.439.439.546.856.136.946.455.362.774.461.457.170.648.070.655.978.050.267.461.849.465.167.345.764.080.448.983.865.436.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax8.96.89.46.38.15.39.35.67.26.48.07.27.76.111.28.58.24.611.28.17.55.910.17.08.510.27.27.59.98.07.57.74.47.08.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl21.716.524.915.219.312.523.313.917.214.719.716.416.813.826.019.318.510.426.418.016.813.224.116.119.824.516.117.323.317.516.120.911.116.921.6

Income Loss From Continuing Operations Including Portion Attributable To Noncontrolling Interest

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value-34-27-38-41-34-28-36-34-25-31-34-31-23-22-23-23-24-30-25-26-33-30-24-25-23-22-24-25-21-22-24-25-27-26-27-25-26
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-3.8-3.1-3.9-5.3-3.4-3.2-3.9-4.3-2.8-3.7-3.7-4.1-2.8-2.8-2.6-3.1-2.9-4.1-2.8-3.7-3.7-3.8-2.9-3.4-2.4-2.6-3.4-3.0-2.4-3.3-3.2-2.5-3.3-2.8-2.8-3.4-2.9

dei:LegalEntity

lnt:Ipl



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-25-20-22-25-15-15-19-21-23-22-23-21-13-11-11-12-14-15-16-17-18-18-15-16-16-13-14-15-17-17-18-18-18-18-20-18
Percentage of NonoperatingIncomeExpense74.475.759.560.545.655.454.861.191.371.567.969.057.053.249.454.260.652.065.165.256.359.062.264.771.761.961.361.681.379.273.272.966.768.374.472.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-2.8-2.4-2.3-3.2-1.6-1.8-2.1-2.6-2.5-2.6-2.5-2.8-1.6-1.5-1.3-1.7-1.7-2.1-1.8-2.4-2.1-2.2-1.8-2.2-1.7-1.6-2.1-1.8-2.0-2.6-2.4-1.8-2.2-1.9-2.1-2.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl-4.9-4.2-3.8-5.7-2.8-3.1-3.6-4.5-4.4-4.8-4.4-5.1-3.0-2.7-2.3-3.1-3.2-4.0-3.3-4.5-3.8-4.2-3.2-4.0-3.1-2.8-3.9-3.3-3.5-5.0-4.5-3.8-4.9-3.8-3.8-4.7

lnt:Wpl



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-12-14-15-17-17-15-17-17-18-17-17-18-20-9-11-10-9-15-9-10-13-12-8-7-6-7-8-8-5-6-7-8-9-9-6-5
Percentage of NonoperatingIncomeExpense36.051.140.841.752.454.348.850.172.056.352.660.484.842.849.444.538.249.036.537.941.939.334.129.828.733.234.233.725.727.930.534.333.733.625.623.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.4-1.6-1.6-2.2-1.8-1.7-1.9-2.1-2.0-2.1-2.0-2.5-2.4-1.2-1.3-1.4-1.1-2.0-1.0-1.4-1.5-1.5-1.0-1.0-0.7-0.9-1.2-1.0-0.6-0.9-1.0-0.8-1.1-1.0-0.7-0.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-3.3-3.9-4.2-5.3-4.3-4.1-4.8-5.3-4.8-4.8-4.8-5.6-5.1-2.7-2.9-3.1-2.4-4.5-2.4-3.1-3.5-3.3-2.4-2.3-1.6-2.1-2.6-2.3-1.5-2.0-2.1-2.3-2.8-2.3-1.9-1.9

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value-181923111551113161262117127182110271120-112132017101239162734-1022642334
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-2.02.22.31.41.50.61.31.71.80.22.92.82.11.50.82.42.61.53.11.62.3-0.21.51.82.22.01.51.44.42.43.63.3-1.32.46.73.13.9

dei:LegalEntity

lnt:Ipl



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-1413612-2-5237-140-3-3-2003-19-2-3-16-26-3-5-26-4-6-11-27-301355
Percentage of IncomeTaxExpenseBenefit75.468.429.917.013.9-48.2-50.416.918.5427.8-54.8-2.8-21.0-27.9-33.34.4-3.728.4-70.5-23.2-17.6884.2-213.7-25.8-24.3-150.0-46.7-50.4-30.3-12.526.7-9.46.67.554.625.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-1.51.50.70.20.2-0.3-0.60.30.30.9-1.6-0.1-0.4-0.4-0.30.1-0.10.4-2.2-0.4-0.4-2.1-3.1-0.5-0.5-3.0-0.7-0.7-1.3-0.31.0-0.3-0.10.23.70.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl-2.72.71.20.40.4-0.5-1.10.50.61.6-2.7-0.1-0.8-0.8-0.50.2-0.20.8-3.9-0.7-0.7-3.9-5.6-0.8-0.9-5.3-1.3-1.3-2.4-0.61.9-0.7-0.20.46.51.5

lnt:Wpl



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-89177148106111231620163320228331822172317262717203119252611212916
Percentage of IncomeTaxExpenseBenefit43.951.374.068.896.7144.687.245.669.6100.088.178.8115.9132.8449.3114.9104.681.7119.1167.9107.8-926.3192.7134.8127.7154.5161.9169.479.4113.791.078.9-106.694.746.570.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.91.11.71.01.50.91.10.81.30.22.52.22.42.03.62.82.71.23.72.62.52.22.82.42.83.12.42.43.52.83.32.61.42.33.12.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-2.22.74.62.43.52.22.81.93.10.56.25.05.24.68.56.26.02.78.75.85.64.96.75.56.47.55.35.58.36.17.17.23.55.58.15.2

Income Taxes Paid Net

us-gaap:IncomeTaxesPaidNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value0-1914-600500092144000000-10-320-30
Percentage of IncomeTaxesPaidNet100.0100.0100.0100.0100.00.00.0100.00.0100.00.0100.0100.0100.0100.0100.00.00.0100.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.0-2.20.20.5-0.70.00.00.60.0-0.00.01.20.30.20.40.60.00.00.00.0-0.00.0-0.20.0-0.40.3-0.0-0.3-0.1

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value013-5-6211004-1-14211-1314-111-12-12-60-12-1014-1422
Percentage of IncomeTaxesPaidNet100.0-6.6229.4-123.3100.00.00.010.00.0-4600.00.0-159.3113.0786.7-340.0325.60.00.0-12500.00.06200.00.0800.0-10500.0-38.5208.714400.0-733.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax0.00.10.4-0.7-0.72.40.20.10.00.5-0.1-1.90.31.5-1.51.9-0.11.6-1.4-1.7-0.70.1-1.4-1.40.20.6-1.92.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl0.00.30.7-1.2-1.24.30.30.10.01.0-0.2-3.50.62.7-2.63.4-0.23.0-2.5-3.2-1.30.2-2.5-2.50.31.0-3.64.6

Comprehensive Income Net Of Tax

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value1721142289712787208102123961719610365131869936182709962155641101606780154693812555791535248
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.813.023.112.312.910.122.412.613.511.218.912.612.18.214.211.411.74.920.39.811.17.818.58.611.618.59.49.317.410.15.112.36.78.416.27.15.4

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value85471434755411295449181234539261163448812019502210520462111224312510619-1910112711100219
Percentage of NetIncomeLoss49.441.462.948.943.847.462.052.739.919.671.846.838.640.689.139.848.621.965.827.450.836.267.432.541.60.070.336.439.30.068.828.1-3.90.080.51.834.00.065.540.420.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.35.414.56.05.74.813.96.65.42.213.65.94.73.312.64.65.71.113.32.75.62.812.52.84.82.513.03.43.73.412.02.8-0.21.19.90.12.91.410.62.91.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl16.49.524.110.810.18.423.611.49.44.023.310.88.86.122.68.410.52.023.85.010.35.222.15.18.74.622.86.46.66.521.45.4-0.42.420.90.35.72.918.85.42.1

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value8949754265387639545349384532694347246739442961345438613443415636314251254435503037
Percentage of NetIncomeLoss51.943.733.043.351.443.336.738.743.755.229.139.444.249.853.150.647.466.737.256.345.247.739.553.849.50.038.350.754.40.036.751.782.00.040.845.255.70.032.557.576.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.85.77.65.36.74.48.24.95.96.25.55.05.34.17.55.85.63.37.65.55.03.77.34.65.84.67.14.85.15.56.45.24.24.95.03.14.74.25.34.14.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl23.913.720.312.915.810.320.612.014.114.213.511.411.69.217.513.112.57.417.712.211.38.317.410.713.410.717.010.811.811.915.111.49.012.413.77.611.410.113.59.79.4

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:RetainedEarnings, lnt:Wpl



Period End2020-03-312019-03-31
Value8965
Percentage of NetIncomeLoss51.951.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.86.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings lnt:Wpl0.00.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value170111226941258520510012093168941006212883963417967966015361108651576569681506534571225173471494743
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.612.722.812.012.79.822.112.313.211.018.612.311.87.913.911.111.44.620.09.410.87.518.28.211.37.918.29.18.19.117.09.54.66.511.96.27.85.715.76.44.9

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value82441414553391265146161204237241143145511716472010218431811022222210316-4698-221896175
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic48.640.162.447.642.645.861.651.538.617.571.345.437.138.388.938.047.316.165.324.749.533.566.929.840.228.269.834.032.832.868.525.2-13.511.680.6-4.529.516.964.936.413.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.05.114.25.75.44.513.66.35.11.913.35.64.43.012.34.25.40.713.12.35.32.512.22.54.62.212.73.12.73.011.62.4-0.60.89.6-0.32.31.010.22.30.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl15.99.023.710.29.67.923.110.98.93.522.810.28.35.522.17.89.91.423.34.49.84.721.54.58.24.022.25.84.85.720.84.6-1.21.620.3-0.64.51.918.14.51.3

us-gaap:PublicUtilityRegulatedOrUnregulatedStatus, us-gaap:StatementBusinessSegments

us-gaap:UnregulatedOperation, us-gaap:AllOtherSegments



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-03-31
Value-29762820-7610-5484-5114-1089-1385-81488
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic-1.34.28.04.91.38.916.7-4.47.110.8-42.610.54.6-2.817.64.3-7.014.29.1-8.713.37.2-5.621.424.411.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.20.91.00.60.31.12.2-0.80.91.3-5.91.20.5-0.61.70.5-1.31.21.0-1.61.20.6-1.02.01.10.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:UnregulatedOperation us-gaap:AllOtherSegments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments

lnt:UtilityBusiness



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value172942168711977202911004917687895518375922918455924916453981715664159512614865146
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic101.384.895.892.095.190.498.791.183.353.2104.492.989.288.8142.689.595.485.9102.882.495.782.0107.085.890.9108.786.792.8105.678.675.6122.088.897.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.810.721.911.012.18.821.811.211.05.819.411.410.57.019.810.010.94.020.67.810.36.119.57.110.319.87.97.617.97.53.414.66.915.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:UtilityBusiness0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value1701112269412585205100120
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.612.722.812.012.79.822.112.313.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:RetainedEarnings, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value824414145533912651
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic48.640.162.447.642.645.861.651.5
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.05.114.25.75.44.513.66.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings lnt:Ipl0.00.00.00.00.00.00.00.0

Net Income Loss Attributable To Noncontrolling Interest

Assets

us-gaap:Assets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1687916700165331612115713154261526914615142411418714114137431346413373130291268512535124951255812312120791208511594113861111611112109811088710733107851025099349628968794819301940092829036
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-31
Value94049277930288308647841183787849762776067682750773237304716167966713670967796587641464616194600058305806569356115530545753995201506650934960488649374892
Percentage of Assets55.755.656.354.855.054.554.953.753.653.654.454.654.454.655.053.653.653.754.053.553.153.553.452.752.452.251.951.551.550.652.752.452.652.652.352.553.254.1
Percentage of Assets55.755.656.354.855.054.554.953.753.653.654.454.654.454.655.053.653.653.754.053.553.153.553.452.752.452.251.951.551.550.652.752.452.652.652.352.553.254.1
Percentage of Assets lnt:Ipl100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-31
Value65516506631363906165615260445910575757565594545653355290540553465305527052635202516651284906488548134804481647824717476242574156405840443936387438893681
Percentage of Assets38.839.038.239.639.239.939.640.440.440.639.639.739.639.641.542.142.342.241.942.342.842.442.342.943.343.243.943.943.944.241.541.842.241.741.541.741.940.7
Percentage of Assets38.839.038.239.639.239.939.640.440.440.639.639.739.639.641.542.142.342.241.942.342.842.442.342.943.343.243.943.943.944.241.541.842.241.741.541.741.940.7
Percentage of Assets lnt:Wpl100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1687916700165331612115713154261526914615142411418714114137431346413373130291268512535124951255812312120791208511594113861111611112109811088710733107851025099349628968794819301940092829036
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value9404927793028830864784118378784976277606768275077323730471616796671367096779658764146461619460005830580656935611553054575399520150665093496048864937
Percentage of LiabilitiesAndStockholdersEquity55.755.656.354.855.054.554.953.753.653.654.454.654.454.655.053.653.653.754.053.553.153.553.452.752.452.251.951.551.550.652.752.452.652.652.352.553.2
Percentage of Assets55.755.656.354.855.054.554.953.753.653.654.454.654.454.655.053.653.653.754.053.553.153.553.452.752.452.251.951.551.550.652.752.452.652.652.352.553.2
Percentage of Assets lnt:Ipl100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Wpl



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
Value6551650663136390616561526044591057575756559454565335529054055346530552705263520251665128490648854813480448164782471747624257415640584044393638743889
Percentage of LiabilitiesAndStockholdersEquity38.839.038.239.639.239.939.640.440.440.639.639.739.639.641.542.142.342.241.942.342.842.442.342.943.343.243.943.943.944.241.541.842.241.741.541.741.9
Percentage of Assets38.839.038.239.639.239.939.640.440.440.639.639.739.639.641.542.142.342.241.942.342.842.442.342.943.343.243.943.943.944.241.541.842.241.741.541.741.9
Percentage of Assets lnt:Wpl100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value55025205496946994682458545704350423141824154405038963862385937903764372437453620359734383435333733313281326631603145313431163014299730133001292729202893277228232681
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets32.631.230.129.229.829.729.929.829.729.529.429.528.928.929.629.930.029.829.829.429.828.529.629.330.029.529.729.029.329.130.430.331.131.131.731.531.131.230.70.00.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value339532713244314531423030283826542514250924322351224722492137203620421995199119081826181418291731171816791663155515351519149813951360139413631294138913301148
Percentage of StockholdersEquity61.762.965.366.967.166.162.161.059.460.058.658.057.758.255.453.754.353.653.252.750.852.853.251.951.651.250.949.248.848.548.146.345.446.345.444.248.048.040.7
Percentage of Assets20.119.619.619.520.019.618.618.217.717.717.217.116.716.816.416.116.316.015.915.515.115.015.815.215.515.115.214.314.314.114.614.014.114.414.413.915.014.70.0
Percentage of Assets lnt:Ipl36.135.334.935.636.336.033.933.833.033.031.731.330.730.829.930.030.429.729.429.028.528.129.528.929.528.929.227.727.827.827.726.826.827.427.526.528.127.20.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value243623632324218521792149214620551900188118091751174417301813177817691756175917231716170317041672166716421633160115951583148014521445144214291406136912541159
Percentage of StockholdersEquity44.345.446.846.546.546.947.047.244.945.043.643.244.844.847.046.947.047.247.047.647.749.549.650.150.150.150.050.750.750.547.548.248.247.947.648.047.345.341.1
Percentage of Assets14.414.214.113.613.913.914.114.113.313.312.812.713.012.913.914.014.114.114.014.014.214.114.714.715.014.814.914.714.914.714.414.615.014.915.115.114.813.90.0
Percentage of Assets lnt:Wpl37.236.336.834.235.334.935.534.833.032.732.432.132.732.733.633.333.333.333.433.133.233.234.734.234.634.233.933.533.833.234.835.035.635.736.336.335.234.10.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value2111210000000000-1-1-10
Percentage of StockholdersEquity0.00.00.00.00.10.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.00.0
Percentage of Assets0.00.00.00.00.00.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.00.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value26742445223621082100204520381947185118451693166315091507151115101506149914941483
Percentage of StockholdersEquity48.647.045.044.944.844.644.644.843.844.143.844.743.945.948.250.152.154.152.955.3
Percentage of Assets15.814.613.513.113.413.313.313.313.013.012.713.312.513.614.015.616.216.60.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value22222222222111111111
Percentage of StockholdersEquity0.00.00.00.10.10.10.10.10.10.10.10.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DeferredCompensationShareBasedPayments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-9-10-10-10-9-9-9-11-11-11-10-8-8-8-7-8-7-7-7-8
Percentage of StockholdersEquity-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.3-0.2-0.3-0.2-0.2-0.3-0.3-0.3-0.3-0.3
Percentage of Assets-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.10.00.0
Percentage of Assets us-gaap:DeferredCompensationShareBasedPayments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value28332765273925972587254525392412238923462177206819381780163015101394128113361205
Percentage of StockholdersEquity51.553.155.155.355.355.555.655.556.556.156.455.656.454.352.050.148.246.247.345.0
Percentage of Assets16.816.616.616.116.516.516.616.516.816.516.316.616.016.015.115.615.014.20.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:AdditionalPaidInCapital, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value24472347232223222322222220271927179717971597
Percentage of StockholdersEquity44.545.146.749.449.648.544.444.342.543.041.4
Percentage of Assets14.514.114.014.414.814.413.313.212.612.711.9
Percentage of Assets us-gaap:AdditionalPaidInCapital lnt:Ipl0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value14591434140913091309130913091259110911091019
Percentage of StockholdersEquity26.527.528.427.928.028.528.628.926.226.526.4
Percentage of Assets8.68.68.58.18.38.58.68.67.87.87.6
Percentage of Assets us-gaap:AdditionalPaidInCapital lnt:Wpl0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value914890887788785774777692683678617
Percentage of StockholdersEquity16.617.117.916.816.816.917.015.916.116.216.0
Percentage of Assets5.45.35.44.95.05.05.14.74.84.84.6
Percentage of Assets us-gaap:RetainedEarnings lnt:Ipl0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value910863849810804774771730725706645
Percentage of StockholdersEquity16.616.617.117.217.216.916.916.817.116.916.7
Percentage of Assets5.45.25.15.05.15.05.15.05.15.04.8
Percentage of Assets us-gaap:RetainedEarnings lnt:Wpl0.00.00.00.00.00.00.00.00.00.00.0

Assets Current

us-gaap:AssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value91287511131027815785112480572590575181474987795870276882610871043913104396210109361011880893870994102892078086694787797710921390
Percentage of AssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.45.26.76.45.25.17.45.55.16.45.35.95.66.67.45.56.16.68.78.57.68.68.38.98.49.18.08.28.19.210.09.38.18.910.09.410.411.815.4

dei:LegalEntity

lnt:Ipl



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
Value435409621399355371715430330476357379330422534275338396601542418556527546497535449431417391467374289323341323428
Percentage of AssetsCurrent47.846.855.838.943.647.463.653.445.552.647.546.644.048.255.739.244.047.955.352.045.853.354.854.153.153.051.148.248.039.445.440.737.037.336.036.939.2
Percentage of Assets2.62.53.82.52.32.44.72.92.33.42.52.82.53.24.12.22.73.24.84.43.54.64.54.84.54.84.14.03.93.64.63.83.03.33.63.54.6
Percentage of Assets lnt:Ipl4.64.46.74.54.14.48.55.54.36.34.75.14.55.87.54.05.05.98.98.26.58.68.59.18.59.27.97.77.67.28.77.25.76.36.96.68.7

lnt:Wpl



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
Value435442450593416384400351369418385382368416377380410423453454466457389401400402388395398468454433379386393367445
Percentage of AssetsCurrent47.850.640.457.751.049.035.643.650.946.251.346.949.147.539.354.153.551.241.743.551.143.840.539.842.839.844.144.345.747.144.247.148.744.541.541.840.7
Percentage of Assets2.62.72.73.72.62.52.62.42.63.02.72.82.73.12.93.03.33.43.63.73.93.83.43.53.63.63.53.63.74.34.44.43.94.04.13.94.8
Percentage of Assets lnt:Wpl6.66.87.19.36.76.36.66.06.47.36.97.06.97.97.07.17.78.08.68.79.08.97.98.28.38.48.18.38.49.810.710.49.49.510.09.511.4

Cash And Cash Equivalents At Carrying Value

us-gaap:CashAndCashEquivalentsAtCarryingValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value5516193170102023951927978884645139549756111614917115321413030114577126159137171140175346745
Percentage of CashAndCashEquivalentsAtCarryingValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.30.11.21.10.10.11.60.00.10.20.10.10.10.10.70.10.00.01.10.40.80.50.10.10.10.10.20.10.50.20.40.30.30.10.50.81.31.70.00.00.01.90.00.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-312008-12-31
Value2591845392321234443772349922545546544522320213522806
Percentage of CashAndCashEquivalentsAtCarryingValue45.357.195.02.938.646.497.132.015.212.951.154.848.840.291.736.962.577.671.43.62.79.341.833.340.044.935.644.38.821.212.99.174.818.40.427.23.13.61.916.70.21.8
Percentage of Assets0.10.11.10.00.00.11.50.00.00.00.00.00.00.00.60.00.00.00.80.00.00.00.00.00.10.00.10.00.00.00.10.00.20.00.00.20.00.10.00.00.00.0
Percentage of Assets lnt:Ipl0.30.12.00.10.00.12.80.00.00.00.10.10.10.01.10.00.00.11.50.00.00.10.10.10.10.10.10.10.10.10.10.10.50.00.00.40.00.10.00.00.00.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-312008-12-31
Value22481633862323322453103548904626406280162222313103527184
Percentage of CashAndCashEquivalentsAtCarryingValue41.127.04.395.933.741.62.750.019.482.834.838.425.051.26.647.727.16.925.689.193.182.120.939.533.85.137.321.715.73.339.48.16.823.751.417.10.80.125.916.210.61.3
Percentage of Assets0.10.00.11.00.00.10.00.00.00.20.00.00.00.00.00.00.00.00.30.40.80.40.00.10.00.00.10.00.10.00.20.00.00.00.20.10.00.00.00.00.20.0
Percentage of Assets lnt:Wpl0.30.10.12.60.10.10.10.00.10.40.10.10.00.10.10.10.00.00.70.91.80.90.00.10.10.00.10.10.20.00.40.10.10.10.60.30.00.00.00.00.50.0

Accounts Receivable Net Current

us-gaap:AccountsReceivableNetCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value39640245142141735046541534348233642442449349131639039742729736142784851068178859894938192188198127140120246
Percentage of AccountsReceivableNetCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.32.42.72.62.72.33.02.82.43.42.43.13.23.73.82.53.13.23.42.43.03.50.70.81.00.70.70.80.90.90.90.81.01.92.11.41.51.32.7

dei:LegalEntity

lnt:Ipl



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
Value2042022582312091532772371452641431941772402669718020023510415821620024225724613011516595183102517510883174
Percentage of AccountsReceivableNetCurrent51.750.457.255.050.143.859.657.242.554.942.745.841.748.854.330.746.350.355.235.043.950.7237.4282.7241.6301.8166.6136.1166.9100.1195.3125.356.339.854.865.4144.5
Percentage of Assets1.21.21.61.41.31.01.81.61.01.91.01.41.31.82.00.81.41.61.90.81.31.81.72.12.32.21.21.11.50.91.81.00.50.81.10.91.9
Percentage of Assets lnt:Ipl2.22.22.82.62.41.83.33.01.93.51.92.62.43.33.71.42.73.03.51.62.53.43.24.04.44.32.32.13.01.73.42.01.01.52.21.73.5

lnt:Wpl



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
Value181190184180198190180170192212185193212226190185192185173166188185767798737074898384728276807484
Percentage of AccountsReceivableNetCurrent45.747.540.842.947.554.338.841.255.944.055.345.449.945.938.858.649.346.640.656.052.143.591.090.192.789.290.488.190.687.890.188.589.640.440.558.169.9
Percentage of Assets1.11.11.11.11.31.21.21.21.31.51.31.41.61.71.51.51.51.51.41.41.61.50.70.70.90.70.60.70.80.80.80.70.90.80.80.80.9
Percentage of Assets lnt:Wpl2.82.92.92.83.23.13.02.93.33.73.33.54.04.33.53.53.63.53.33.23.63.61.61.62.11.51.51.61.91.72.01.72.01.92.01.92.2

Inventory Raw Materials And Supplies

us-gaap:InventoryRawMaterialsAndSupplies



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1051001061051051011061091091059994888689838381838281727275726971686463616161586161646153
Percentage of InventoryRawMaterialsAndSupplies100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.60.60.60.70.70.70.70.70.80.70.70.70.70.60.70.70.70.70.70.70.70.60.60.70.60.60.60.60.60.60.60.60.60.60.60.70.70.70.6

dei:LegalEntity

lnt:Ipl



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
Value60556058565559606160525148465048474546474842414340393937343333323231333433
Percentage of InventoryRawMaterialsAndSupplies57.654.756.455.254.154.655.555.656.157.453.154.755.053.755.957.756.456.155.757.759.057.656.757.156.356.655.755.253.352.854.253.753.253.854.355.654.4
Percentage of Assets0.40.30.40.40.40.40.40.40.40.40.40.40.40.30.40.40.40.40.40.40.40.30.40.40.40.40.40.30.30.30.30.30.30.30.40.40.4
Percentage of Assets lnt:Ipl0.60.60.60.70.70.70.70.80.80.80.70.70.70.60.70.70.70.70.70.70.70.60.70.70.70.70.70.70.60.60.60.60.60.60.70.70.7

lnt:Wpl



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
Value42434344454244454442433936363532343335323129293029282929292826262725262625
Percentage of InventoryRawMaterialsAndSupplies40.242.940.942.243.142.341.741.340.939.944.041.841.141.939.939.240.841.242.239.938.740.140.939.941.141.541.842.544.745.243.543.544.643.943.742.841.7
Percentage of Assets0.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.20.30.30.30.30.30.30.30.30.30.30.30.30.30.30.3
Percentage of Assets lnt:Wpl0.60.70.70.70.70.70.70.80.80.70.80.70.70.70.70.60.60.60.70.60.60.60.60.60.60.60.60.60.60.60.60.60.70.60.70.70.7

Other Assets Current

us-gaap:OtherAssetsCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value1371011371511538012611385871011127095989864792174352271162942892098411912515743413460153132185192111112
Percentage of OtherAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.80.60.80.91.00.50.80.80.60.60.70.80.50.70.80.80.50.61.73.51.91.02.52.51.90.81.11.21.50.40.40.40.61.61.42.02.01.21.2

dei:LegalEntity

lnt:Ipl



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
Value28302221214338292332393614273733132811530813665166168106343850542411112633212222
Percentage of OtherAssetsCurrent20.729.516.114.413.953.930.026.027.036.838.832.820.929.037.633.921.435.452.970.760.055.656.758.050.840.632.740.234.556.828.532.444.022.016.112.120.0
Percentage of Assets0.20.20.10.10.10.30.20.20.20.20.30.30.10.20.30.30.10.20.92.51.10.51.41.51.00.30.40.50.50.20.10.10.30.30.20.20.2
Percentage of Assets lnt:Ipl0.30.30.20.20.20.50.50.40.30.40.50.50.20.40.50.50.20.41.74.72.11.02.72.81.80.60.70.91.00.50.20.20.50.70.40.50.5

lnt:Wpl



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
Value88618610810320607157136463452053555120945183231131099217495763162025271624159
Percentage of OtherAssetsCurrent64.360.763.272.067.525.847.863.067.215.363.756.864.621.754.556.379.526.043.311.936.619.838.637.844.120.741.645.640.437.049.974.245.510.618.88.18.4
Percentage of Assets0.50.40.50.70.70.10.40.50.40.10.50.50.30.20.40.40.40.20.70.40.70.21.01.00.80.20.50.50.60.10.20.30.30.20.30.20.1
Percentage of Assets lnt:Wpl1.30.91.41.71.70.31.01.21.00.21.21.20.90.41.01.01.00.41.81.01.60.52.32.21.90.41.01.21.40.30.50.60.70.40.60.40.2

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value13685135271313112854126651246212005116951143911234109311060810448102799920984696269519936691739050893887638566842683268141802779137838738472487081703769376866682367306192
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets81.181.079.479.780.680.878.680.080.379.277.477.277.676.976.177.676.876.274.674.574.974.075.675.275.874.974.173.773.772.772.073.073.572.673.273.872.672.568.5

dei:LegalEntity

lnt:Ipl



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
Value7589748072837080694767816432619360885926576455865503543552205127499349254804468746314554443342794194413640213962390338583799374236923676363236153703
Percentage of PropertyPlantAndEquipmentNet55.555.355.555.154.954.453.653.053.252.852.752.752.752.952.652.151.951.751.351.151.251.050.650.049.849.749.449.449.349.251.551.652.152.252.452.755.0
Percentage of Assets45.044.844.143.944.244.042.142.442.841.840.840.640.940.640.140.439.839.438.338.138.337.738.237.637.737.236.636.436.435.837.137.738.337.938.338.939.9
Percentage of Assets lnt:Ipl80.780.678.380.280.480.676.878.979.877.975.074.475.274.472.975.474.473.470.971.272.270.571.671.371.971.370.670.670.670.770.471.972.972.273.274.075.0

lnt:Wpl



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
Value5691563854495377532252875183511849624917478246354523442642894227414141034094402839663938390138663818378137363684363336013147309130493021298429442846
Percentage of PropertyPlantAndEquipmentNet41.641.741.541.842.042.443.243.843.443.843.843.743.343.143.242.943.043.143.743.943.844.144.545.145.345.445.945.945.945.942.642.643.142.943.042.942.3
Percentage of Assets33.733.833.033.433.934.333.935.034.834.733.933.733.633.132.933.333.032.832.632.732.832.633.634.034.334.034.033.833.933.430.731.131.731.231.531.730.7
Percentage of Assets lnt:Wpl86.986.786.384.286.385.985.886.686.285.485.585.084.883.779.379.178.177.977.877.476.876.879.579.279.378.777.677.077.075.673.974.475.174.775.876.073.2

Long Term Investments

us-gaap:LongTermInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value469467453443433431424420414396458354346337329324323346353349343344343338332329324321321319314308303300299296292289281
Percentage of LongTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.82.82.72.72.82.82.82.92.92.83.22.62.62.52.52.62.62.82.82.82.82.93.03.03.03.03.03.03.03.03.13.13.23.13.23.23.13.13.1

Deferred Tax Assets Liabilities Net

Other Assets Noncurrent

us-gaap:OtherAssetsNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value181272726872891038672692118142291010143538414355676885991111081059876829293121130137172
Percentage of OtherAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets10.70.40.40.40.50.60.70.60.50.50.20.10.10.20.10.10.10.10.30.30.30.40.50.60.60.80.91.01.01.01.00.80.91.01.01.31.41.51.9

dei:LegalEntity

lnt:Ipl



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
Value13793128191918201616148864344516151212182629292121201919171919214949
Percentage of OtherAssetsNoncurrent76.143.938.728.526.820.419.519.222.420.239.746.244.320.840.440.441.134.247.139.331.328.933.238.742.334.622.118.819.118.319.723.023.220.823.140.735.7
Percentage of Assets8.20.20.20.10.10.10.10.10.10.10.10.10.00.00.00.00.00.00.10.10.10.10.20.20.30.30.20.20.20.20.20.20.20.20.20.50.5
Percentage of Assets lnt:Ipl14.70.30.30.20.20.20.20.20.20.20.10.10.10.10.10.10.10.10.20.20.20.20.30.40.50.50.40.40.40.40.40.30.40.40.41.01.0

lnt:Wpl



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
Value42523192124625743292725232017686920232729384238545163585753343644474957
Percentage of OtherAssetsNoncurrent23.531.926.931.733.070.155.350.340.639.2120.1126.3139.676.173.478.062.662.356.962.367.767.769.762.756.163.351.856.353.954.754.644.544.548.550.540.741.9
Percentage of Assets2.50.10.10.10.20.40.40.30.20.20.20.20.20.10.10.10.10.10.20.20.20.20.30.40.30.50.50.60.50.50.50.30.40.50.50.50.6
Percentage of Assets lnt:Wpl6.50.40.30.30.41.00.90.70.50.50.50.40.40.30.10.20.10.20.40.50.50.60.80.90.81.11.11.31.21.21.30.80.91.11.21.31.5

Liabilities Current

us-gaap:LiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value16502054208219491587164415481257207321491470120811651162136913731348135999099110231214174117331384143310521072103810209459577738557747607788661076
Percentage of LiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets9.812.312.612.110.110.710.18.614.615.110.48.88.78.710.510.810.810.97.98.18.510.115.015.212.512.99.69.99.79.59.29.68.08.88.28.28.39.311.9

dei:LegalEntity

lnt:Ipl



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
Value835830882494484607798815798827603490493521487488484531551543644705771771507524517527520468490466414422389435482
Percentage of LiabilitiesCurrent50.640.442.425.430.536.951.664.938.538.541.040.642.444.935.635.636.039.155.754.863.058.144.344.536.736.649.149.250.246.051.948.853.649.450.257.355.7
Percentage of Assets4.95.05.33.13.13.95.25.65.65.84.33.63.73.93.73.83.94.34.44.45.35.86.66.84.64.74.74.84.94.34.84.74.34.44.14.75.2
Percentage of Assets lnt:Ipl8.99.09.55.65.67.29.510.410.510.97.86.56.77.16.87.27.27.98.18.210.010.912.412.98.79.09.19.49.48.69.19.08.28.37.88.99.8

lnt:Wpl



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
Value700690508743677694601343352396589531420394303353343336295297314310459472431451419435422385287286250257216217292
Percentage of LiabilitiesCurrent42.433.624.438.242.742.238.927.317.018.440.143.936.134.022.225.725.524.829.830.030.725.526.427.331.231.539.840.640.737.830.429.932.330.127.928.633.8
Percentage of Assets4.14.13.14.64.34.53.92.32.52.84.23.93.13.02.32.82.72.72.42.42.62.64.04.13.94.13.84.03.93.62.82.92.62.72.32.33.2
Percentage of Assets lnt:Wpl10.710.68.011.611.011.310.05.86.16.910.59.77.97.55.66.66.56.45.65.76.16.19.49.79.09.48.79.19.08.16.86.96.26.45.55.67.5

Long Term Debt Current

us-gaap:LongTermDebtCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value3576576567062562565063568558551055443143143133133331831834925093583584811111111111101
Percentage of LongTermDebtCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.13.94.04.41.61.73.32.46.06.00.70.00.00.02.42.52.52.50.00.31.51.54.34.53.23.20.40.00.00.00.00.00.00.00.00.00.00.01.1

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-31
Value2002002000250350350350100000015015015018838383800
Percentage of LongTermDebtCurrent56.030.430.50.049.498.340.940.995.10.00.00.00.082.082.030.437.010.710.779.30.00.0
Percentage of Assets1.21.21.20.01.62.42.52.50.70.00.00.00.01.21.21.31.70.30.30.30.00.0
Percentage of Assets lnt:Ipl2.12.22.10.03.04.54.64.61.30.00.00.00.02.32.32.43.10.70.70.70.00.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312016-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-31
Value150150150400250250250000030303030888800
Percentage of LongTermDebtCurrent42.022.822.856.697.597.549.40.00.00.00.091.316.716.76.21.72.42.417.60.00.0
Percentage of Assets0.90.90.92.51.61.61.60.00.00.00.00.20.30.30.30.10.10.10.10.00.0
Percentage of Assets lnt:Wpl2.32.32.46.34.14.14.10.00.00.00.00.60.60.60.60.20.20.20.20.00.0

Accounts Payable Current

us-gaap:AccountsPayableCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value375422497422387543498431363477478381369445365353323402438374356427471475388365368391368339418337263308314305300336331
Percentage of AccountsPayableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.22.53.02.62.53.53.32.92.53.43.42.82.73.32.82.82.63.23.53.03.03.54.14.23.53.33.43.63.43.14.13.42.73.23.33.33.23.63.7

dei:LegalEntity

lnt:Ipl



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
Value184207290216227304279203183220224163149186172160153197251222199259286262214187195213204163231171136118116119146
Percentage of AccountsPayableCurrent49.149.058.351.358.656.156.047.250.546.247.043.040.441.847.345.447.449.057.359.255.960.760.755.355.351.352.954.655.448.155.450.951.838.437.039.243.4
Percentage of Assets1.11.21.81.31.42.01.81.41.31.61.61.21.11.41.31.31.21.62.01.81.72.12.52.31.91.71.82.01.91.52.31.71.41.21.21.31.6
Percentage of Assets lnt:Ipl2.02.23.12.52.63.63.32.62.42.92.92.22.02.62.42.42.32.93.73.43.14.04.64.43.73.23.43.83.73.04.33.32.72.32.32.53.0

lnt:Wpl



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
Value13615915115010418016217313420119715015719212213011113612298107112118152114120117124115126133106859893100118
Percentage of AccountsPayableCurrent36.337.930.435.527.033.332.640.337.142.341.239.542.543.333.537.034.333.827.926.130.226.425.132.029.432.932.031.731.437.331.931.532.232.029.832.735.2
Percentage of Assets0.81.00.90.90.71.21.11.20.91.41.41.11.21.40.91.00.91.11.00.80.90.91.01.31.01.11.11.11.11.21.31.10.91.01.01.11.3
Percentage of Assets lnt:Wpl2.12.52.42.31.72.92.72.92.33.53.52.82.93.62.32.42.12.62.31.92.12.22.43.12.42.52.42.62.52.73.12.62.12.42.42.63.0

Taxes Payable Current

Other Liabilities Current

us-gaap:OtherLiabilitiesCurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value407425389262249260255247251260217265272222273284304296250264232262204215191133223244196113999387127152161163160117
Percentage of OtherLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.42.52.41.61.61.71.71.71.81.81.51.92.01.72.12.22.42.42.02.11.92.21.81.91.71.22.02.21.81.11.00.90.91.31.61.71.71.71.3

dei:LegalEntity

lnt:Ipl



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
Value26520719787150561731701279092194131578518219869125148122906811961741131371143634313132262835
Percentage of OtherLiabilitiesCurrent65.148.850.833.560.421.568.068.750.734.742.873.348.225.731.464.365.123.449.956.052.834.333.555.532.356.251.056.458.231.934.434.035.525.317.417.422.1
Percentage of Assets1.61.21.20.51.00.41.11.20.90.60.71.41.00.40.71.41.60.61.01.21.00.70.61.10.60.71.01.31.10.30.30.30.30.30.30.30.4
Percentage of Assets lnt:Ipl2.82.22.11.01.70.72.12.21.71.21.22.61.80.81.22.73.01.01.82.21.91.41.12.01.11.32.02.52.10.70.60.60.60.60.50.60.7

lnt:Wpl



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
Value128741131091124895958951108112123549112014679868282465460643659721263238333432293338
Percentage of OtherLiabilitiesCurrent31.517.529.241.645.218.537.238.535.819.750.142.445.124.633.242.548.126.834.531.235.617.826.927.833.427.726.529.664.628.438.635.939.225.319.220.624.3
Percentage of Assets0.80.40.70.70.70.30.60.70.60.40.80.80.90.40.71.01.20.60.70.70.70.40.50.50.60.30.50.71.20.30.40.30.40.30.30.40.4
Percentage of Assets lnt:Wpl2.01.11.81.71.80.81.61.61.60.91.92.12.31.01.72.32.81.51.61.61.60.91.11.21.30.81.21.52.70.70.90.80.80.80.70.91.0

Long Term Debt

us-gaap:FairValueByMeasurementBasis

us-gaap:LongTermDebt

us-gaap:CarryingReportedAmountFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-31
Value619161906191614456185502575454834912486643604359432043204130383532923338333933363153314231233138
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets36.737.137.538.135.835.737.737.534.534.330.931.732.132.331.730.728.429.330.030.028.728.929.129.1
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueByMeasurementBasis, dei:LegalEntity

us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value31473147314628502552
Percentage of LongTermDebt50.850.850.846.446.4
Percentage of Assets18.618.819.017.716.5
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure lnt:Ipl0.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value19331932193221811834
Percentage of LongTermDebt31.231.231.235.533.3
Percentage of Assets11.511.611.713.511.9
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure lnt:Wpl0.00.00.00.00.0

Long Term Debt Noncurrent

us-gaap:LongTermDebtNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value583355335535543853625246524851274056401042554354431643153816358835223522385537173606360627992829298029773104314131213136282827522728270327032703270327032404
Percentage of LongTermDebtNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets34.633.133.533.734.134.034.435.128.528.330.131.732.132.329.328.328.128.230.730.229.929.824.124.926.826.828.328.929.129.127.627.728.327.928.529.128.829.126.6

dei:LegalEntity

lnt:Ipl



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
Value2947294729462850266725522551218121022056209521942154215321531924185718561868173016181618137013701520152013361364134413591359135913341309130813081308
Percentage of LongTermDebtNoncurrent50.553.353.252.449.848.648.642.651.851.349.250.449.949.956.453.652.752.748.546.544.944.948.948.451.051.043.043.443.143.348.149.448.948.448.448.448.4
Percentage of Assets17.517.617.817.717.016.516.714.914.814.514.816.016.016.116.515.214.814.914.914.113.413.411.812.013.713.712.212.512.512.613.313.713.913.513.814.114.1
Percentage of Assets lnt:Ipl31.331.831.732.330.930.330.527.827.627.027.329.229.429.530.128.327.727.727.626.325.225.122.122.826.126.223.524.324.324.925.226.126.325.726.426.826.5

lnt:Wpl



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
Value1783178217821781158515841584183418331833153615351535153515341534153415331543154315431543129313231323132313231331133113311082108210821082108210821081
Percentage of LongTermDebtNoncurrent30.632.232.232.829.630.230.235.845.245.736.135.335.635.640.242.843.643.540.041.542.842.846.246.844.444.442.642.442.742.538.339.339.740.040.040.040.0
Percentage of Assets10.610.710.811.110.110.310.412.512.912.910.911.211.411.511.812.112.212.312.312.512.812.811.211.611.911.912.112.212.412.310.610.911.211.211.411.611.7
Percentage of Assets lnt:Wpl27.227.428.227.925.725.826.231.031.831.827.528.228.829.028.428.728.929.129.329.729.930.126.427.127.527.527.527.928.228.025.426.026.726.827.527.927.8

Deferred Tax Liabilities Noncurrent

Pension And Other Postretirement Defined Benefit Plans Liabilities Noncurrent

us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value452484476487493509487488488504481482481489455452446451416417417421201202203206356359360364310309309312235241299303323
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.72.92.93.03.13.33.23.33.43.63.43.53.63.73.53.63.63.63.33.43.53.51.71.81.81.93.23.33.43.43.03.13.23.22.52.63.23.33.6

dei:LegalEntity

lnt:Ipl



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
Value16116716517117417816817017117317117117217316116016016014114114214246474748120121122122991001001017274110
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent35.734.634.735.135.435.034.634.835.134.535.635.635.735.435.435.635.935.533.933.934.033.823.023.323.623.533.733.733.933.832.132.432.632.630.831.036.3
Percentage of Assets1.01.01.01.11.11.21.11.21.21.21.21.31.31.31.21.31.31.31.11.11.21.20.40.40.40.41.11.11.11.11.01.01.01.10.80.81.2
Percentage of Assets lnt:Ipl1.71.81.81.92.02.12.02.22.22.32.22.32.42.42.32.42.42.42.12.12.22.20.70.80.80.82.12.22.22.31.81.92.02.01.51.52.2

lnt:Wpl



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
Value20321020321021421720720921021320420520520718618618618817817917918084858788156158159159127127127128103103119
Percentage of PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent45.043.642.743.243.442.842.542.843.142.442.442.542.742.440.941.241.741.842.842.943.042.841.942.243.142.844.044.044.343.941.141.041.240.944.042.939.2
Percentage of Assets1.21.31.21.31.41.41.41.41.51.51.41.51.51.61.41.51.51.51.41.51.51.50.70.70.80.81.41.51.51.51.21.31.31.31.11.11.3
Percentage of Assets lnt:Wpl3.13.23.23.33.53.53.43.53.73.73.73.83.93.93.43.53.53.63.43.43.53.51.71.71.81.83.33.33.43.43.03.13.13.22.62.73.1

Minority Interest

Other Liabilities Noncurrent

us-gaap:OtherLiabilitiesNoncurrent



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value349298305413442287286310313306296288297279300297310306333342259260267253262273271275257262269245248259251212208208294
Percentage of OtherLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.11.81.82.62.81.91.92.12.22.22.12.12.22.12.32.32.52.42.72.82.12.22.32.22.42.52.52.52.42.42.62.52.62.72.72.32.22.33.3

dei:LegalEntity

lnt:Ipl



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
Value269253251360365220221242239242238228221214229227223229231243177185182174171169181183178182189186188199187143141
Percentage of OtherLiabilitiesNoncurrent77.084.882.187.282.576.877.178.076.279.180.579.374.276.776.376.772.174.969.470.968.371.368.168.765.561.866.766.769.369.770.676.275.776.874.467.667.8
Percentage of Assets1.61.51.52.22.31.41.41.71.71.71.71.71.61.61.81.81.81.81.82.01.51.51.61.51.51.51.71.71.71.71.91.92.02.12.01.51.5
Percentage of Assets lnt:Ipl2.92.72.74.14.22.62.63.13.13.23.13.03.02.93.23.43.33.43.43.72.82.92.92.92.92.93.23.33.23.43.53.63.73.93.82.92.9

lnt:Wpl



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
Value162168164159188178175174172167162163168159162157169162181177159155138133142153153155141144148135135136124132135
Percentage of OtherLiabilitiesNoncurrent46.556.453.938.642.562.061.256.355.054.754.956.856.757.154.152.954.552.954.551.961.459.752.052.554.355.956.556.455.055.155.355.154.652.749.562.464.7
Percentage of Assets1.01.01.01.01.21.21.11.21.21.21.21.21.31.21.21.21.31.31.41.41.31.31.21.21.31.41.41.41.31.31.51.41.41.41.31.41.5
Percentage of Assets lnt:Wpl2.52.62.62.53.12.92.93.03.02.92.93.03.23.03.02.93.23.13.53.43.13.02.82.73.03.23.23.33.03.03.53.23.33.43.23.43.5

Stockholders Equity

us-gaap:StockholdersEquity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-312007-12-31
Value55025205496946994682458545704350423141824154405038963862385937903764372437453620359734383435333733313281326631603145313431163014299730133001292729202893277228232681
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets32.631.230.129.229.829.729.929.829.729.529.429.528.928.929.629.930.029.829.829.429.828.529.629.330.029.529.729.029.329.130.430.331.131.131.731.531.131.230.70.00.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value339532713244314531423030283826542514250924322351224722492137203620421995199119081826181418291731171816791663155515351519149813951360139413631294138913301148
Percentage of StockholdersEquity61.762.965.366.967.166.162.161.059.460.058.658.057.758.255.453.754.353.653.252.750.852.853.251.951.651.250.949.248.848.548.146.345.446.345.444.248.048.040.7
Percentage of Assets20.119.619.619.520.019.618.618.217.717.717.217.116.716.816.416.116.316.015.915.515.115.015.815.215.515.115.214.314.314.114.614.014.114.414.413.915.014.70.0
Percentage of Assets lnt:Ipl36.135.334.935.636.336.033.933.833.033.031.731.330.730.829.930.030.429.729.429.028.528.129.528.929.528.929.227.727.827.827.726.826.827.427.526.528.127.20.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-312009-12-312008-12-31
Value243623632324218521792149214620551900188118091751174417301813177817691756175917231716170317041672166716421633160115951583148014521445144214291406136912541159
Percentage of StockholdersEquity44.345.446.846.546.546.947.047.244.945.043.643.244.844.847.046.947.047.247.047.647.749.549.650.150.150.150.050.750.750.547.548.248.247.947.648.047.345.341.1
Percentage of Assets14.414.214.113.613.913.914.114.113.313.312.812.713.012.913.914.014.114.114.014.014.214.114.714.715.014.814.914.714.914.714.414.615.014.915.115.114.813.90.0
Percentage of Assets lnt:Wpl37.236.336.834.235.334.935.534.833.032.732.432.132.732.733.633.333.333.333.433.133.233.234.734.234.634.233.933.533.833.234.835.035.635.736.336.335.234.10.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value2111210000000000-1-1-10
Percentage of StockholdersEquity0.00.00.00.00.10.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.00.0
Percentage of Assets0.00.00.00.00.00.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.00.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value26742445223621082100204520381947185118451693166315091507151115101506149914941483
Percentage of StockholdersEquity48.647.045.044.944.844.644.644.843.844.143.844.743.945.948.250.152.154.152.955.3
Percentage of Assets15.814.613.513.113.413.313.313.313.013.012.713.312.513.614.015.616.216.60.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value22222222222111111111
Percentage of StockholdersEquity0.00.00.00.10.10.10.10.10.10.10.10.00.00.00.00.00.00.00.00.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DeferredCompensationShareBasedPayments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value-9-10-10-10-9-9-9-11-11-11-10-8-8-8-7-8-7-7-7-8
Percentage of StockholdersEquity-0.2-0.2-0.2-0.2-0.2-0.2-0.2-0.3-0.3-0.3-0.3-0.2-0.3-0.2-0.2-0.3-0.3-0.3-0.3-0.3
Percentage of Assets-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.1-0.10.00.0
Percentage of Assets us-gaap:DeferredCompensationShareBasedPayments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-312007-12-31
Value28332765273925972587254525392412238923462177206819381780163015101394128113361205
Percentage of StockholdersEquity51.553.155.155.355.355.555.655.556.556.156.455.656.454.352.050.148.246.247.345.0
Percentage of Assets16.816.616.616.116.516.516.616.516.816.516.316.616.016.015.115.615.014.20.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:AdditionalPaidInCapital, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value24472347232223222322222220271927179717971597
Percentage of StockholdersEquity44.545.146.749.449.648.544.444.342.543.041.4
Percentage of Assets14.514.114.014.414.814.413.313.212.612.711.9
Percentage of Assets us-gaap:AdditionalPaidInCapital lnt:Ipl0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value14591434140913091309130913091259110911091019
Percentage of StockholdersEquity26.527.528.427.928.028.528.628.926.226.526.4
Percentage of Assets8.68.68.58.18.38.58.68.67.87.87.6
Percentage of Assets us-gaap:AdditionalPaidInCapital lnt:Wpl0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value914890887788785774777692683678617
Percentage of StockholdersEquity16.617.117.916.816.816.917.015.916.116.216.0
Percentage of Assets5.45.35.44.95.05.05.14.74.84.84.6
Percentage of Assets us-gaap:RetainedEarnings lnt:Ipl0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value910863849810804774771730725706645
Percentage of StockholdersEquity16.616.617.117.217.216.916.916.817.116.916.7
Percentage of Assets5.45.25.15.05.15.05.15.05.15.04.8
Percentage of Assets us-gaap:RetainedEarnings lnt:Wpl0.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value222222222222222211111111111111111111111
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value283327652739259725872545253924122389234623242228220521772181211620982068209719791973193819341837183217801767166116481630161215111495151015001425142113941281
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets16.816.616.616.116.516.516.616.516.816.516.516.216.416.316.716.716.716.616.716.116.316.016.716.116.516.016.115.315.415.115.715.215.515.615.815.315.115.014.2

dei:LegalEntity

lnt:Ipl



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
Value914890887788785774777692683678701619615617631555561554614532550537552485501493507429439448456384398433456358382
Percentage of RetainedEarningsAccumulatedDeficit32.332.232.430.430.430.430.628.728.628.930.227.827.928.429.026.326.826.829.326.927.927.828.626.427.427.728.725.926.727.528.325.426.728.730.425.127.4
Percentage of Assets5.45.35.44.95.05.05.14.74.84.85.04.54.64.64.84.44.54.44.94.34.64.54.84.34.54.44.63.94.14.24.53.94.14.54.83.94.1
Percentage of Assets lnt:Ipl9.79.69.58.99.19.29.38.89.08.99.18.38.48.58.88.28.48.39.18.18.68.38.98.18.68.58.97.77.98.28.57.47.98.59.27.37.7

lnt:Wpl



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
Value910863849810804774771730725706684666659645788753743731734698691678679647642617608575570557545517510507494471459
Percentage of RetainedEarningsAccumulatedDeficit32.131.231.031.231.130.430.430.330.430.129.429.929.929.736.235.635.435.335.035.335.035.035.135.235.134.734.434.734.634.233.834.234.133.632.933.132.9
Percentage of Assets5.45.25.15.05.15.05.15.05.15.04.84.84.94.86.15.95.95.95.85.75.75.65.95.75.85.65.55.35.35.25.35.25.35.25.25.14.9
Percentage of Assets lnt:Wpl13.913.313.512.713.012.612.812.412.612.312.212.212.412.214.614.114.013.914.013.413.413.213.813.213.312.812.612.012.111.712.812.512.612.512.612.211.8

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value211121000000000000000000000000000000-1-1-1
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value1601512329518185507-15489100381168333205144281228175178202314127315154293198215261189
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax17.517.223.512.118.39.854.6-18.99.711.742.122.039.125.815.637.327.123.819.828.235.115.937.420.630.823.128.127.721.3

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value2534491276-43365-261-65-3020291176105-151551166723124170321671001056578128
Percentage of NetCashProvidedByUsedInOperatingActivities15.722.821.312.842.4-51.372.1169.5-73.0-30.653.154.552.851.3-10.655.251.038.113.261.454.125.553.165.036.032.836.349.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.73.95.01.67.8-5.039.4-32.0-7.1-3.622.312.020.613.2-1.720.613.89.12.617.319.04.019.913.411.17.610.213.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl4.86.98.32.813.8-8.966.8-55.1-12.4-6.538.421.839.124.3-3.037.825.416.84.732.534.87.535.224.420.013.619.626.9

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value148631518612211111984141104131841458218712712373145721575813010612810594173
Percentage of NetCashProvidedByUsedInOperatingActivities92.542.165.289.867.5130.423.6-54.6158.7104.534.450.143.639.9130.545.454.142.081.935.750.145.941.369.143.853.143.966.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.27.215.310.912.412.812.910.315.512.214.511.017.110.320.316.914.610.016.210.117.67.315.514.213.512.312.318.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl39.517.640.726.429.430.232.325.537.127.935.525.237.023.347.338.232.922.338.122.339.716.336.832.931.428.526.644.6

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-179-426-254-242-364-251-637-93-85-424-445-322-303-414-271-280-220-306-142-219-250-277-271-192-176-119-135-233-232
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-19.6-48.4-25.7-30.7-37.0-28.7-68.6-11.4-9.3-49.5-49.2-42.2-35.6-52.0-29.3-37.2-26.1-41.4-15.9-30.6-28.0-34.5-32.2-25.6-18.6-13.9-17.6-24.7-26.1

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-52-182-129-132-221-100-48910455-212-187-169-136-258-143-168-123-192-34-128-156-176-180-99-96-83-61-109
Percentage of NetCashProvidedByUsedInInvestingActivities29.542.951.054.860.840.076.8-112.3-65.350.242.152.544.962.353.159.956.062.924.058.862.363.566.451.954.669.545.447.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-5.8-20.8-13.1-16.8-22.5-11.5-52.712.86.1-24.9-20.7-22.2-16.0-32.4-15.6-22.3-14.6-26.0-3.8-18.0-17.4-21.9-21.4-13.3-10.1-9.7-8.0-11.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl-10.2-36.8-21.7-30.1-40.0-20.3-89.422.110.6-45.1-35.6-40.4-30.3-59.4-27.9-40.9-26.9-48.3-6.8-33.7-32.0-40.9-37.8-24.2-18.3-17.4-15.4-23.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-124-222-116-97-120-138-143-196-128-195-147-173-149-152-121-114-91-98-97-83-78-86-82-80-70-76-63-124
Percentage of NetCashProvidedByUsedInInvestingActivities69.352.246.040.333.055.322.5210.9151.146.133.153.649.236.744.740.741.532.268.438.131.231.130.541.939.963.647.153.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-13.6-25.3-11.8-12.4-12.2-15.9-15.4-24.1-14.0-22.8-16.3-22.6-17.5-19.1-13.1-15.1-10.8-13.3-10.9-11.7-8.7-10.7-9.8-10.7-7.4-8.9-8.3-13.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-33.2-61.4-31.4-30.0-29.0-37.6-38.6-59.5-33.7-52.2-39.9-51.7-38.0-43.2-30.5-34.2-24.3-29.8-25.5-25.7-19.7-24.0-23.3-24.8-17.2-20.6-17.9-32.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value609347302176-56365231-934266153-291322050-9-349-26-23195-4939-112-46-60-617
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.610.64.838.317.8-6.539.428.4-1.140.07.320.0-3.516.622.20.1-1.1-0.45.5-3.6-2.624.3-5.95.2-11.8-5.4-7.9-6.50.9

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value43-27259119139-793541558242-1477-3978234125301083-1614411-1-7184-20
Percentage of NetCashProvidedByUsedInFinancingActivities72.1-29.6547.639.679.3140.297.067.2-90.870.7-21.450.7131.159.1114.31537.5-57.0-987.1220.2-15.071.473.9-23.8-2.86.8-39.0-7.133.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.8-3.126.215.214.1-9.138.219.11.028.3-1.610.2-4.69.825.41.60.64.112.00.5-1.818.01.4-0.1-0.82.10.6-2.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl8.4-5.543.427.225.1-16.164.832.81.751.3-2.718.5-8.718.045.43.01.27.721.41.0-3.433.52.5-0.3-1.43.81.1-4.3

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-5153-189171-62826111-311101689168-64-11-31-10-61-30-3572-51-24-53-21-31-48
Percentage of NetCashProvidedByUsedInFinancingActivities-9.0165.1-400.456.6-3.6-50.87.348.1319.432.425.558.3-5.451.8-31.3-1475.0336.6341.9-124.6118.8152.436.9104.4-62.848.046.351.878.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.617.4-19.121.7-0.63.32.913.6-3.413.01.911.70.28.6-7.0-1.6-3.7-1.4-6.8-4.3-3.99.0-6.1-3.3-5.6-2.5-4.1-5.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-1.442.4-50.952.6-1.57.87.233.6-8.229.64.626.70.419.5-16.2-3.5-8.3-3.2-16.0-9.5-8.920.0-14.6-7.6-13.1-5.8-8.8-12.4

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value1601512329518185507-15489100381168333205144281228175178202314127315154293198215261189
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax17.517.223.512.118.39.854.6-18.99.711.742.122.039.125.815.637.327.123.819.828.235.115.937.420.630.823.128.127.721.3

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value2534491276-43365-261-65-3020291176105-151551166723124170321671001056578128
Percentage of NetCashProvidedByUsedInOperatingActivities15.722.821.312.842.4-51.372.1169.5-73.0-30.653.154.552.851.3-10.655.251.038.113.261.454.125.553.165.036.032.836.349.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax2.73.95.01.67.8-5.039.4-32.0-7.1-3.622.312.020.613.2-1.720.613.89.12.617.319.04.019.913.411.17.610.213.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl4.86.98.32.813.8-8.966.8-55.1-12.4-6.538.421.839.124.3-3.037.825.416.84.732.534.87.535.224.420.013.619.626.9

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value148631518612211111984141104131841458218712712373145721575813010612810594173
Percentage of NetCashProvidedByUsedInOperatingActivities92.542.165.289.867.5130.423.6-54.6158.7104.534.450.143.639.9130.545.454.142.081.935.750.145.941.369.143.853.143.966.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax16.27.215.310.912.412.812.910.315.512.214.511.017.110.320.316.914.610.016.210.117.67.315.514.213.512.312.318.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl39.517.640.726.429.430.232.325.537.127.935.525.237.023.347.338.232.922.338.122.339.716.336.832.931.428.526.644.6

Net Income Loss

us-gaap:NetIncomeLoss



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value1721142289712787208102123961719610365131869936182709962155641101606780154693812555791535248
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax18.813.023.112.312.910.122.412.613.511.218.912.612.18.214.211.411.74.920.39.811.17.818.58.611.618.59.49.317.410.15.112.36.78.416.27.15.4

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value85471434755411295449181234539261163448812019502210520462111224312510619-1910112711100219
Percentage of NetIncomeLoss49.441.462.948.943.847.462.052.739.919.671.846.838.640.689.139.848.621.965.827.450.836.267.432.541.60.070.336.439.30.068.828.1-3.90.080.51.834.00.065.540.420.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.35.414.56.05.74.813.96.65.42.213.65.94.73.312.64.65.71.113.32.75.62.812.52.84.82.513.03.43.73.412.02.8-0.21.19.90.12.91.410.62.91.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl16.49.524.110.810.18.423.611.49.44.023.310.88.86.122.68.410.52.023.85.010.35.222.15.18.74.622.86.46.66.521.45.4-0.42.420.90.35.72.918.85.42.1

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value8949754265387639545349384532694347246739442961345438613443415636314251254435503037
Percentage of NetIncomeLoss51.943.733.043.351.443.336.738.743.755.229.139.444.249.853.150.647.466.737.256.345.247.739.553.849.50.038.350.754.40.036.751.782.00.040.845.255.70.032.557.576.9
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.85.77.65.36.74.48.24.95.96.25.55.05.34.17.55.85.63.37.65.55.03.77.34.65.84.67.14.85.15.56.45.24.24.95.03.14.74.25.34.14.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl23.913.720.312.915.810.320.612.014.114.213.511.411.69.217.513.112.57.417.712.211.38.317.410.713.410.717.010.811.811.915.111.49.012.413.77.611.410.113.59.79.4

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:RetainedEarnings, lnt:Wpl



Period End2020-03-312019-03-31
Value8965
Percentage of NetIncomeLoss51.951.4
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax9.86.7
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax us-gaap:RetainedEarnings lnt:Wpl0.00.0

Depreciation Depletion And Amortization

us-gaap:DepreciationDepletionAndAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value146143143142136130129
Percentage of DepreciationDepletionAndAmortization100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value85838382777473
Percentage of DepreciationDepletionAndAmortization58.758.058.257.856.356.957.3

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value59595859585554
Percentage of DepreciationDepletionAndAmortization40.441.141.041.442.842.341.9

Increase Decrease In Other Operating Capital Net

us-gaap:IncreaseDecreaseInOtherOperatingCapitalNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value10-404427-22-975-1035-55-339-18-11-1789-44-132-315-9571-360313-2231
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value18118-43430272-1011-21-122439-20-17-9-4-12-5018-4728-196-20
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet184.2-2.72.931.4196.8-43.340.4-23.122.5-3.6297.128.8115.1106.9-143.944.646.41166.7-27.713.7-210.353.225.9128.93177.8-521.647.591.4

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-24-71827-24-434362-35-312630-20-50-16-4-2332-7-29-617-51-13-16-15
Percentage of IncreaseDecreaseInOtherOperatingCapitalNet-245.517.441.4100.7109.5450.557.4-575.0-100.956.4-762.978.1111.943.1-4.1-18.410.71553.3100.023.9-501.76.925.014.7122.2-373.0-115.170.5

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-179-426-254-242-364-251-637-93-85-424-445-322-303-414-271-280-220-306-142-219-250-277-271-192-176-119-135-233-232
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-19.6-48.4-25.7-30.7-37.0-28.7-68.6-11.4-9.3-49.5-49.2-42.2-35.6-52.0-29.3-37.2-26.1-41.4-15.9-30.6-28.0-34.5-32.2-25.6-18.6-13.9-17.6-24.7-26.1

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-52-182-129-132-221-100-48910455-212-187-169-136-258-143-168-123-192-34-128-156-176-180-99-96-83-61-109
Percentage of NetCashProvidedByUsedInInvestingActivities29.542.951.054.860.840.076.8-112.3-65.350.242.152.544.962.353.159.956.062.924.058.862.363.566.451.954.669.545.447.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-5.8-20.8-13.1-16.8-22.5-11.5-52.712.86.1-24.9-20.7-22.2-16.0-32.4-15.6-22.3-14.6-26.0-3.8-18.0-17.4-21.9-21.4-13.3-10.1-9.7-8.0-11.6
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl-10.2-36.8-21.7-30.1-40.0-20.3-89.422.110.6-45.1-35.6-40.4-30.3-59.4-27.9-40.9-26.9-48.3-6.8-33.7-32.0-40.9-37.8-24.2-18.3-17.4-15.4-23.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-124-222-116-97-120-138-143-196-128-195-147-173-149-152-121-114-91-98-97-83-78-86-82-80-70-76-63-124
Percentage of NetCashProvidedByUsedInInvestingActivities69.352.246.040.333.055.322.5210.9151.146.133.153.649.236.744.740.741.532.268.438.131.231.130.541.939.963.647.153.3
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-13.6-25.3-11.8-12.4-12.2-15.9-15.4-24.1-14.0-22.8-16.3-22.6-17.5-19.1-13.1-15.1-10.8-13.3-10.9-11.7-8.7-10.7-9.8-10.7-7.4-8.9-8.3-13.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-33.2-61.4-31.4-30.0-29.0-37.6-38.6-59.5-33.7-52.2-39.9-51.7-38.0-43.2-30.5-34.2-24.3-29.8-25.5-25.7-19.7-24.0-23.3-24.8-17.2-20.6-17.9-32.0

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value277636351278374553380
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-30
Value165246188261244
Percentage of PaymentsToAcquirePropertyPlantAndEquipment59.470.267.669.964.1

lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-30
Value11210490112136
Percentage of PaymentsToAcquirePropertyPlantAndEquipment40.629.832.430.135.9

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value609347302176-56365231-934266153-291322050-9-349-26-23195-4939-112-46-60-617
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax6.610.64.838.317.8-6.539.428.4-1.140.07.320.0-3.516.622.20.1-1.1-0.45.5-3.6-2.624.3-5.95.2-11.8-5.4-7.9-6.50.9

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value43-27259119139-793541558242-1477-3978234125301083-1614411-1-7184-20
Percentage of NetCashProvidedByUsedInFinancingActivities72.1-29.6547.639.679.3140.297.067.2-90.870.7-21.450.7131.159.1114.31537.5-57.0-987.1220.2-15.071.473.9-23.8-2.86.8-39.0-7.133.2
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax4.8-3.126.215.214.1-9.138.219.11.028.3-1.610.2-4.69.825.41.60.64.112.00.5-1.818.01.4-0.1-0.82.10.6-2.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Ipl8.4-5.543.427.225.1-16.164.832.81.751.3-2.718.5-8.718.045.43.01.27.721.41.0-3.433.52.5-0.3-1.43.81.1-4.3

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-5153-189171-62826111-311101689168-64-11-31-10-61-30-3572-51-24-53-21-31-48
Percentage of NetCashProvidedByUsedInFinancingActivities-9.0165.1-400.456.6-3.6-50.87.348.1319.432.425.558.3-5.451.8-31.3-1475.0336.6341.9-124.6118.8152.436.9104.4-62.848.046.351.878.8
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax-0.617.4-19.121.7-0.63.32.913.6-3.413.01.911.70.28.6-7.0-1.6-3.7-1.4-6.8-4.3-3.99.0-6.1-3.3-5.6-2.5-4.1-5.1
Percentage of RevenueFromContractWithCustomerExcludingAssessedTax lnt:Wpl-1.442.4-50.952.6-1.57.87.233.6-8.229.64.626.70.419.5-16.2-3.5-8.3-3.2-16.0-9.5-8.920.0-14.6-7.6-13.1-5.8-8.8-12.4

Proceeds From Issuance Of Long Term Debt

us-gaap:ProceedsFromIssuanceOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302016-12-312015-12-312014-12-31
Value30003006500050055005000810
Percentage of ProceedsFromIssuanceOfLongTermDebt100.00.0100.0100.00.00.0100.0100.00.0100.00.0100.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302016-12-312016-09-302015-12-312015-09-302014-12-312014-09-302013-12-31
Value300325030252100203110130310460
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DebtInstrument, us-gaap:LongtermDebtType, dei:LegalEntity

lnt:TermLoanCreditAgreementThroughAprilTwoThousandandTwenty, lnt:TermLoanCreditAgreement, lnt:AlliantEnergyFinanceLLC



Period End2020-03-31
Value300
Percentage of RepaymentsOfLongTermDebt99.9
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations lnt:TermLoanCreditAgreementThroughAprilTwoThousandandTwenty lnt:TermLoanCreditAgreement lnt:AlliantEnergyFinanceLLC0.0

Repayments Of Long Term Debt

us-gaap:RepaymentsOfLongTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312017-09-302016-12-312016-09-302015-12-312015-09-302014-12-312014-09-302013-12-31
Value300325030252100203110130310460
Percentage of RepaymentsOfLongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of LongTermDebtAndCapitalLeaseObligations0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:DebtInstrument, us-gaap:LongtermDebtType, dei:LegalEntity

lnt:TermLoanCreditAgreementThroughAprilTwoThousandandTwenty, lnt:TermLoanCreditAgreement, lnt:AlliantEnergyFinanceLLC



Period End2020-03-31
Value300
Percentage of RepaymentsOfLongTermDebt99.9
Percentage of LongTermDebtAndCapitalLeaseObligations0.0
Percentage of LongTermDebtAndCapitalLeaseObligations lnt:TermLoanCreditAgreementThroughAprilTwoThousandandTwenty lnt:TermLoanCreditAgreement lnt:AlliantEnergyFinanceLLC0.0

Debt Instrument Interest Rate Stated Percentage

Effective Income Tax Rate Continuing Operations

us-gaap:EffectiveIncomeTaxRateContinuingOperations



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302010-09-302010-06-30
Value-0.1220.0099999999999999950.0920.1030.106-0.003999999999999990.0530.1170.12-0.0239999999999999940.1320.180.1480.00500000000000000440.0540.1720.1770.0090000000000000080.1320.1360.171-0.020999999999999990.0730.170.1570.0980.1330.1270.2040.1950.390.213-0.2370.2920.304
Percentage of EffectiveIncomeTaxRateContinuingOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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-0.1980.0339999999999999960.0460.0380.036-0.01-0.0480.0410.0590.048-0.132-0.013-0.102-0.014-0.0220.023-0.0170.026999999999999996-0.195-0.157-0.077-0.10699999999999998-0.337-0.194-0.122-0.306-0.247-0.24-0.126-0.121.254-0.033-2.3330.0590.2580.215
Percentage of EffectiveIncomeTaxRateContinuingOperations162.3340.050.036.934.0250.0-90.635.049.2-200.0-100.0-7.2-68.9-280.0-40.713.4-9.6300.0-147.7-115.4-45.0509.5-461.6-114.1-77.7-312.2-185.7-189.0-61.8-61.5321.5-15.5984.40.088.470.7

lnt:Wpl



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-0.101-0.00200000000000000180.1850.1550.1820.0060000000000000050.1180.1350.178-0.0620.3160.3050.310.00100000000000000090.3260.3220.325-0.0090000000000000080.3280.3220.330.0100000000000000090.280.340.3240.3070.3310.320.3550.3460.4410.3440.3110.3250.3730.349
Percentage of EffectiveIncomeTaxRateContinuingOperations82.8-20.0201.1150.5171.7-150.0222.6115.4148.3258.3239.4169.4209.520.0603.7187.2183.6-100.0248.5236.8193.0-47.6383.6200.0206.4313.3248.9252.0174.0177.4113.1161.5-131.20.0127.7114.8

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

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod

lnt:PerformanceRestrictedStockUnit



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
Value54897.00.010979.00.080837.00.00.00.074163.00.00.01546.063804.00.00.034809.033776.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod100.00.0100.00.0100.00.00.00.0100.00.00.0100.0100.00.00.0100.0100.0

us-gaap:PerformanceShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value54897.00.010979.00.080837.00.00.00.074163.00.00.01546.063804.00.00.034809.033776.00.00.00.045403.00.00.00.051221.049093.045612.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod100.00.0100.00.0100.00.00.00.0100.00.00.0100.0100.00.00.0100.0100.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RestrictedStockUnitsRSU



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
Value59936.00.09410.00.095938.00.00.00.063568.00.00.01325.054688.00.00.029838.028952.0
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod109.20.085.70.0118.70.00.00.085.70.00.085.785.70.00.085.785.7

Deferred Tax Liabilities

Deferred Tax Assets Net

Unrecognized Tax Benefits

Deferred Tax Assets Valuation Allowance

Unrecognized Tax Benefits Increases Resulting From Current Period Tax Positions

Operating Lease Right Of Use Asset

Cash And Cash Equivalents Period Increase Decrease

Proceeds From Repayments Of Short Term Debt

us-gaap:ProceedsFromRepaymentsOfShortTermDebt



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-66-12-40-239188304-70-26962-110116105585-49745350-123190-99-2124586-5810-20-15160
Percentage of ProceedsFromRepaymentsOfShortTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-312015-09-302014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value000-1156450-1257945-4443090-670-111-383800-4117
Percentage of ProceedsFromRepaymentsOfShortTermDebt-0.0-0.0-0.048.134.316.6176.8-29.373.940.03.429.115.70.0135.90.090.417.982.80.0-0.0-378.9-86.1

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value131680-138326712-45-199121213840-3420519000-146-112-2873-2-15
Percentage of ProceedsFromRepaymentsOfShortTermDebt-20.6-1378.7-0.057.917.522.0-17.01.69.0181.310.4114.766.3698.369.027.410.439.3-0.00.0-0.069.0-24.62.948.5673.411.5100.0

dei:LegalEntity

lnt:CollectionsReinvestedInReceivables

lnt:Ipl



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
Value541557592487555526549483517363347434501456499422440409480417505460520475541481435491522369442482410475518407
Percentage of CollectionsReinvestedInReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:CreditLossesNetOfRecoveries

lnt:Ipl



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
Value273258416732450002321-163232132232231
Percentage of CreditLossesNetOfRecoveries100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:IncreaseDecreaseinGasStoredUnderground



Period End2020-03-312019-03-312018-03-312017-03-31
Value-13-33-28-25
Percentage of IncreaseDecreaseinGasStoredUnderground100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-03-312018-03-31
Value-13-20-16
Percentage of IncreaseDecreaseinGasStoredUnderground97.862.559.2

us-gaap:StatementScenario, us-gaap:LongTermContractForPurchaseOfElectricPower

lnt:LongtermContractforPurchaseofElectricPowerBuyoutPayment

srt:ScenarioForecast, lnt:DAECPPA



Period End2020-09-30
Value110
Percentage of LongtermContractforPurchaseofElectricPowerBuyoutPayment100.0

us-gaap:AllocatedShareBasedCompensationExpense



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
Value2107344453551314754023713341202102221
Percentage of AllocatedShareBasedCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value154122221220102322011401121101001110
Percentage of AllocatedShareBasedCompensationExpense51.955.856.055.955.354.557.154.954.555.854.956.253.150.054.552.152.853.166.752.253.154.450.054.854.850.052.651.9100.052.450.0100.053.854.553.853.8

lnt:Wpl



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
Value143111121220101322011301110100001010
Percentage of AllocatedShareBasedCompensationExpense40.739.440.041.238.340.940.541.239.444.241.237.543.850.043.243.743.444.933.343.543.841.841.741.941.942.547.440.7100.042.943.8100.038.540.942.338.5

us-gaap:AssetRetirementObligationAccretionExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value11111111111110111101
Percentage of AssetRetirementObligationAccretionExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value11111001000000000000
Percentage of AssetRetirementObligationAccretionExpense70.662.568.466.762.556.256.262.556.260.058.341.740.028.650.045.550.050.055.663.6

us-gaap:AssetRetirementObligationLiabilitiesIncurred



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value27000250010103740-1200160
Percentage of AssetRetirementObligationLiabilitiesIncurred100.00.0100.00.0100.00.0100.0100.0100.0100.0100.0100.00.0100.00.00.0100.00.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value2700025000073570-1200160
Percentage of AssetRetirementObligationLiabilitiesIncurred100.00.0100.00.0100.00.00.00.0100.075.2100.077.00.0100.00.00.098.80.0

us-gaap:AssetRetirementObligationLiabilitiesSettled



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value12400234210422000010
Percentage of AssetRetirementObligationLiabilitiesSettled100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value12400131010020000000
Percentage of AssetRetirementObligationLiabilitiesSettled93.396.697.885.785.764.376.928.325.970.6100.04.8100.037.533.350.060.00.090.0100.0

us-gaap:CapitalExpendituresIncurredButNotYetPaid



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value156-586619167634941144072-1513954-2217105-3117431191916398599422847
Percentage of CapitalExpendituresIncurredButNotYetPaid100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value92-68621010644492568527-1449-7447-38-3368216202946602316
Percentage of CapitalExpendituresIncurredButNotYetPaid59.1117.594.054.363.669.898.660.347.1-771.438.16.731.717.134.226.345.3121.5-18.483.569.685.9127.276.453.961.056.058.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value6211395716-31573-745-139042-111349-217632-1-61333351610
Percentage of CapitalExpendituresIncurredButNotYetPaid39.7-19.25.845.734.225.8-6.837.751.01114.362.792.765.077.653.676.047.36.398.915.327.6-7.8-42.033.339.235.238.836.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect



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
Value40-18225156-7-222235-16-5183-21
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value15-1761780-5-223231-100200
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect38.496.7701.6-0.371.4100.798.07.412.3-1.186.77.142.1

lnt:Wpl



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
Value18-5-154159-413-1-1820-20-2
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect44.72.9-607.5102.258.4-0.71.38.0321.1110.7-66.7-25.0-110.5

us-gaap:CommonStockDividendsPerShareDeclared



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value0.380.3550.3550.3550.3350.3350.3350.3150.3150.3150.293750.293750.58750.550.550.550.510.510.510.470.470.470.450.450.450.4250.4250.4250.3950.3950.395
Percentage of CommonStockDividendsPerShareDeclared100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ConcentrationRiskByBenchmark

us-gaap:ConcentrationRiskPercentage1

us-gaap:WorkforceSubjectToCollectiveBargainingArrangements



Period End2020-03-312019-03-312017-03-31
Value0.530.550.56
Percentage of ConcentrationRiskPercentage1100.0100.0100.0

us-gaap:WorkforceSubjectToCollectiveBargainingArrangementsExpiringWithinOneYear



Period End2020-03-312019-03-312017-03-31
Value0.180.260.19
Percentage of ConcentrationRiskPercentage134.047.333.9

us-gaap:ConcentrationRiskByBenchmark, dei:LegalEntity

us-gaap:WorkforceSubjectToCollectiveBargainingArrangements, lnt:Ipl



Period End2020-03-31
Value0.61
Percentage of ConcentrationRiskPercentage1115.1

us-gaap:WorkforceSubjectToCollectiveBargainingArrangements, lnt:Wpl



Period End2020-03-31
Value0.82
Percentage of ConcentrationRiskPercentage1154.7

us-gaap:WorkforceSubjectToCollectiveBargainingArrangementsExpiringWithinOneYear, lnt:Ipl



Period End2020-03-31
Value0.45
Percentage of ConcentrationRiskPercentage184.9

us-gaap:ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset



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
Value188-492236178-1243587120106-5421149
Percentage of ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value188-492236178-1243587120106-5421149
Percentage of ConsiderationReceivedForBeneficialInterestObtainedForTransferringFinancialAsset100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CumulativeEffectOnRetainedEarningsNetOfTax1



Period End2020-03-31
Value8
Percentage of CumulativeEffectOnRetainedEarningsNetOfTax1100.0

us-gaap:AdjustmentsForNewAccountingPronouncements, us-gaap:StatementEquityComponents

us-gaap:AccountingStandardsUpdate201613, us-gaap:RetainedEarnings



Period End2020-03-31
Value8
Percentage of CumulativeEffectOnRetainedEarningsNetOfTax1100.0

us-gaap:DeferredIncomeTaxesAndTaxCredits



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-22233-1214281617365327227302322135813291161352231-428
Percentage of DeferredIncomeTaxesAndTaxCredits100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-800000.0-900000.0-800000.0-800000.0-800000.0-900000.0-800000.0-900000.0-800000.0-900000.0-1000000.0-900000.0-1000000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-8-9-9-9-9-8-8-8-8-9-9-9-9
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses1075.01011.11137.51137.51137.5977.81100.0977.81100.01044.4940.01044.4940.0

us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-300000.0-400000.0-400000.0-300000.0-400000.0-300000.0-400000.0-300000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses37.544.450.037.550.033.350.033.3

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-500000.0-400000.0-400000.0-400000.0-400000.0-500000.0-500000.0-500000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses62.544.450.050.050.055.662.555.6

us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-3-3-3-4-3-3-3-3
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses462.5433.3487.5500.0487.5411.1462.5422.2

us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-4-4-4-4-4-4-4-4
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses512.5488.9550.0550.0550.0477.8537.5477.8

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfPriorServiceCostCredit

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.00.0-100000.0-100000.00.0-100000.00.0-100000.00.00.0-100000.00.0-100000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.0100.0100.00.0100.00.0100.00.00.0100.00.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-200000.0-200000.0-200000.0-100000.0-200000.0-200000.0-200000.0-100000.0-200000.0-100000.0-100000.0-100000.0-100000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.0200.0100.00.0200.00.0100.00.00.0100.00.0100.0

us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.0-100000.00.0-100000.00.0-100000.00.0-100000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.0-0.0100.00.0100.00.0100.0

us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-100000.00.0-100000.00.0-100000.0-100000.00.0-100000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.0100.0-0.00.0100.00.0100.0

us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-100000.0-100000.00.00.0-100000.00.00.0-100000.0
Percentage of DefinedBenefitPlanAmortizationOfPriorServiceCostCredit0.00.0-0.0-0.00.0-0.00.0100.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1111111111111
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value17151515151717171716161616
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets1338.51153.81258.31153.81250.01160.01160.01166.71160.01093.31086.71025.01093.3

us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value10000111
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets76.969.275.069.275.073.373.373.3

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value200000.0100000.0200000.0200000.0100000.0100000.0200000.0100000.0
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets15.47.716.715.48.36.713.36.7

us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value87777888
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets623.1538.5583.3546.2583.3546.7540.0546.7

us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value76666777
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets584.6507.7541.7507.7541.7506.7506.7506.7

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value1222212112222
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value10121212121111111112121212
Percentage of DefinedBenefitPlanInterestCost600.0590.5568.2590.5595.2615.8585.0615.8615.8604.8577.3609.5581.8

us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value700000.0900000.0800000.0900000.0800000.0800000.0700000.0800000.0
Percentage of DefinedBenefitPlanInterestCost38.942.936.442.938.142.135.042.1

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value700000.0700000.0900000.0900000.0800000.0800000.0800000.0700000.0
Percentage of DefinedBenefitPlanInterestCost38.933.340.942.938.142.140.036.8

us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value55555555
Percentage of DefinedBenefitPlanInterestCost277.8271.4254.5271.4271.4284.2265.0284.2

us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value45555555
Percentage of DefinedBenefitPlanInterestCost261.1257.1240.9257.1257.1268.4250.0268.4

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value2222222222222
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value8888856558988
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost414.3348.0352.0366.7352.0256.5260.9268.2256.5314.3346.4325.9314.3

us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value300000.0700000.0600000.0700000.0600000.0400000.0400000.0500000.0
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost14.328.024.029.224.017.417.422.7

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value11111111
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost61.952.056.054.256.065.265.263.6

us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value24444222
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost104.8160.0160.0170.8160.0117.4117.4127.3

us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value24444222
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0160.0164.0166.7164.0126.1121.7127.3

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-03-312018-12-312018-09-302017-12-312017-09-30
Value-400000
Percentage of DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1100.00.00.00.00.0100.0

us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanServiceCost

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0000011111111
Percentage of DefinedBenefitPlanServiceCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PensionPlansDefinedBenefit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value2222233333333
Percentage of DefinedBenefitPlanServiceCost337.5300.0312.5266.7300.0272.7310.0300.0272.7246.2258.3238.5258.3

us-gaap:RetirementPlanType, dei:LegalEntity

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value300000.0300000.0300000.0400000.0300000.0400000.0400000.0500000.0
Percentage of DefinedBenefitPlanServiceCost37.537.537.544.437.536.440.050.0

us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value300000.0400000.0300000.0300000.0300000.0400000.0400000.0400000.0
Percentage of DefinedBenefitPlanServiceCost37.550.037.533.337.536.440.040.0

us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value11111111
Percentage of DefinedBenefitPlanServiceCost212.5175.0200.0166.7187.5172.7180.0190.0

us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value10000111
Percentage of DefinedBenefitPlanServiceCost125.0112.5112.588.9112.5100.0110.0110.0

us-gaap:DepreciationAndAmortization



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value1461431431421361301291271201191201151071021041021021019910010099979595929292838083818278756574
Percentage of DepreciationAndAmortization100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value8583827774737064646661535352525252515251504948484747474747464545434443
Percentage of DepreciationAndAmortization58.758.257.856.356.957.355.553.853.754.853.250.151.550.651.351.451.451.651.951.750.850.851.051.051.751.351.456.658.356.355.654.755.759.467.0

lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-30
Value5958595855545554545352524948474746454546464544444243433533353536332919
Percentage of DepreciationAndAmortization40.441.041.442.842.341.943.745.345.444.445.949.047.646.846.446.246.246.045.645.946.347.046.746.846.446.646.542.841.143.143.143.942.438.730.6

us-gaap:Energy, us-gaap:TradingActivityByType

us-gaap:DerivativeNonmonetaryNotionalAmountEnergyMeasure

lnt:FtrsMwhs, us-gaap:Commodity



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-31
Value4-6-6203-6193-5163-5163
Percentage of DerivativeNonmonetaryNotionalAmountEnergyMeasure100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity

lnt:FtrsMwhs, us-gaap:Commodity, lnt:Ipl



Period End2020-03-312019-12-312019-09-30
Value2-3-3
Percentage of DerivativeNonmonetaryNotionalAmountEnergyMeasure47.748.450.8

lnt:FtrsMwhs, us-gaap:Commodity, lnt:Wpl



Period End2020-03-312019-12-312019-09-30
Value2-3-2
Percentage of DerivativeNonmonetaryNotionalAmountEnergyMeasure52.351.649.2

us-gaap:Energy, us-gaap:TradingActivityByType

us-gaap:DerivativeNonmonetaryNotionalAmountMass

us-gaap:CoalContract, us-gaap:Commodity



Period End2020-03-312019-12-312019-09-30
Value5-10
Percentage of DerivativeNonmonetaryNotionalAmountMass100.0100.0100.0

us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity

us-gaap:CoalContract, us-gaap:Commodity, lnt:Ipl



Period End2020-03-312019-12-312019-09-30
Value200
Percentage of DerivativeNonmonetaryNotionalAmountMass42.942.867.8

us-gaap:CoalContract, us-gaap:Commodity, lnt:Wpl



Period End2020-03-312019-12-312019-09-30
Value200
Percentage of DerivativeNonmonetaryNotionalAmountMass57.157.232.2

us-gaap:Energy, us-gaap:TradingActivityByType

us-gaap:DerivativeNonmonetaryNotionalAmountVolume

srt:Fuel, us-gaap:Commodity



Period End2020-03-312019-12-312019-09-30
Value400
Percentage of DerivativeNonmonetaryNotionalAmountVolume100.0100.0100.0

us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity

srt:Fuel, us-gaap:Commodity, lnt:Wpl



Period End2020-03-312019-12-312019-09-30
Value400
Percentage of DerivativeNonmonetaryNotionalAmountVolume100.0100.0100.0

us-gaap:DividendsCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value938584848378787777
Percentage of DividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value594242414242414241
Percentage of DividendsCommonStock63.449.349.749.850.253.453.454.554.1

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value423635363635343535
Percentage of DividendsCommonStock45.342.342.442.843.044.544.545.445.2

us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value938584848378787777
Percentage of DividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:RetainedEarnings, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value5942424142424142
Percentage of DividendsCommonStock63.449.349.749.850.253.453.454.5

us-gaap:RetainedEarnings, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value4236353636353435
Percentage of DividendsCommonStock45.342.342.442.843.044.544.545.4

us-gaap:DividendsPreferredStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value222222222222222222222222222104343464
Percentage of DividendsPreferredStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value22222222222222222222222222283333353
Percentage of DividendsPreferredStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.084.380.076.980.079.578.687.182.6

us-gaap:EarningsPerShareBasicAndDiluted



Period End2020-03-312019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-31
Value0.70.40.530.35999999999999990.870.430.520.39999999999999990.730.410.440.27999999999999980.570.370.850.29999999999999981.590.60.870.541.380.560.971.420.590.631.360.60.321.10.460.66
Percentage of EarningsPerShareBasicAndDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense



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
Value022111110220101222001301110100001010
Percentage of EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value011000000110001111000100000000000000
Percentage of EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense57.158.657.150.061.553.858.360.055.654.552.466.753.850.058.855.250.055.050.055.653.856.240.058.353.850.050.054.50.055.650.0100.050.055.645.560.0

lnt:Wpl



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
Value010000000000000100000100000000000000
Percentage of EmployeeServiceShareBasedCompensationTaxBenefitFromCompensationExpense42.937.938.140.038.538.541.733.344.440.942.950.038.550.041.244.840.945.00.044.446.240.660.041.738.543.837.545.50.033.350.00.040.044.436.440.0

us-gaap:Range, us-gaap:PublicUtility

us-gaap:EnvironmentalExitCostsAnticipatedCost

srt:Maximum, us-gaap:NaturalGasProcessingPlant



Period End2020-03-312019-12-312019-09-30
Value29-10
Percentage of EnvironmentalExitCostsAnticipatedCost100.0100.00.0

srt:Minimum, us-gaap:NaturalGasProcessingPlant



Period End2020-03-312019-12-312019-09-30
Value120-1
Percentage of EnvironmentalExitCostsAnticipatedCost41.4-0.00.0

us-gaap:Range, us-gaap:PublicUtility, dei:LegalEntity

srt:Maximum, us-gaap:NaturalGasProcessingPlant, lnt:Ipl



Period End2020-03-312019-12-312019-09-30
Value240-1
Percentage of EnvironmentalExitCostsAnticipatedCost82.8-0.00.0

srt:Minimum, us-gaap:NaturalGasProcessingPlant, lnt:Ipl



Period End2020-03-312019-12-312019-09-30
Value1000
Percentage of EnvironmentalExitCostsAnticipatedCost34.5-0.00.0

us-gaap:FairValueByAssetClass

us-gaap:FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value-31120-2-5260-9-1-48-3323-544-30-3-18-17
Percentage of FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByAssetClass, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-22110-1-716-1
Percentage of FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss74.2161.590.60.053.8132.864.41600.0

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0010-1191
Percentage of FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss25.8-61.59.40.046.2-32.835.6-1500.0

us-gaap:FairValueByAssetClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1

us-gaap:CommodityContract



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-31120-5-6250-9-1-48-3522-544-31-5-21-19-18-31-1216380-1-2-23-12
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByAssetClass, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value-22110-3-816-1
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings174.2161.590.6-400.057.1122.765.4800.0

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0010-2181
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings125.8-61.59.4500.042.9-22.734.6-700.0

us-gaap:FairValueByAssetClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value0000000000000000000003-10000
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales0.00.00.00.0100.0100.0100.00.00.00.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:FairValueByAssetClass, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value0.00.00.00.0100000.0300000.0100000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales0.00.00.00.050.0100.050.0

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value0.00.00.00.0100000.00.0100000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales0.00.00.00.050.00.050.0

us-gaap:FairValueByAssetClass

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements

lnt:DeferredProceedsOfReceivablesSold



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value049-22-36-58124-35-87101-10654-2162-106165791723-1224459-1633-2232-1752-55-72-48-202163-2346
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-30
Value333465677686618-40223412171916181512874-3-63-3-3
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements-1300.06.1-13.4-13.2-10.24.5-17.5-8.97.3-6.515.5-31.010.1-17.6-2.40.511.89.8-3.09.320.2-103.656.9-71.257.8-88.122.9-14.8-10.8-9.615.4-29.05.414.7-8.2

us-gaap:FairValueByAssetClass, dei:LegalEntity

lnt:DeferredProceedsOfReceivablesSold, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value049-22-36-58124-35-87
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value22235446
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements-966.74.1-9.8-10.2-8.73.6-13.8-7.3

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value11010111
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements-333.32.0-3.6-3.0-1.50.9-3.7-1.6

us-gaap:IncomeLossFromEquityMethodInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value13171112101391021111011111099104111166111111111010101091099999
Percentage of IncomeLossFromEquityMethodInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

lnt:InvestmentInAtc



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
Value111510109128789101111109810
Percentage of IncomeLossFromEquityMethodInvestments82.186.090.578.787.297.790.874.340.881.5100.098.2100.097.298.996.7101.9

lnt:NonutilityWindInvestmentInOklahoma



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value20110212000
Percentage of IncomeLossFromEquityMethodInvestments16.43.410.210.1-1.023.856.8-2.00.00.0

lnt:OtherEquityMethodInvestments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value00010010000000000000-1-3000000000000
Percentage of IncomeLossFromEquityMethodInvestments1.50.66.011.02.8-6.210.21.92.33.40.01.80.02.81.13.3-1.9-12.21.83.5-20.0-50.02.61.81.82.72.83.70.02.8-5.34.07.11.1

us-gaap:IncreaseDecreaseInAccountsPayable



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-03-312015-06-302015-03-312014-06-302014-03-312013-03-312011-03-312010-03-31
Value-659-42-1325-59440-41-317-32102512-36
Percentage of IncreaseDecreaseInAccountsPayable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Wpl



Period End2020-03-312019-06-302019-03-312018-06-302018-03-312017-03-312016-03-312015-03-312012-03-312011-03-31
Value-29-2812-23-25-154-10-19
Percentage of IncreaseDecreaseInAccountsPayable46.894.867.249.438.661.749.0-12.20.0-872.7

us-gaap:IncreaseDecreaseInAccountsReceivable



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value11911215978121150-18236014743-25-11-3620411147-2522-27-647-48-1035512-630-23
Percentage of IncreaseDecreaseInAccountsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value12510115596112140-19237816620145-32-633-437-2825-19222-17-974834-18-10
Percentage of IncreaseDecreaseInAccountsReceivable105.590.397.6123.892.693.7105.4105.2112.947.0-59.0-49.189.6-33.381.4-41.078.5114.3114.570.5-33.348.136.794.287.9269.028.6-2600.0

us-gaap:IncreaseDecreaseInDeferredIncomeTaxes



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312014-09-302012-03-312011-03-312010-03-31
Value-49-8-11-17-16-23-3921-1419-40-28-32-30-25-8943-20-26-28-58-13-4513
Percentage of IncreaseDecreaseInDeferredIncomeTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Wpl



Period End2020-03-312019-03-312016-03-31
Value-32-419
Percentage of IncreaseDecreaseInDeferredIncomeTaxes65.123.745.4

us-gaap:IncreaseDecreaseInPensionAndPostretirementObligations



Period End2020-03-312019-03-312011-03-312010-03-31
Value-31-15-434
Percentage of IncreaseDecreaseInPensionAndPostretirementObligations100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInRegulatoryLiabilities



Period End2020-03-312019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302013-03-312012-03-312011-03-312010-03-31
Value-38-4014-13-6-1234-19-45-33143-370-28-6-21-33-6-501520-26159-11
Percentage of IncreaseDecreaseInRegulatoryLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-31
Value-39-13-10-15-3-6462-65-16-121265
Percentage of IncreaseDecreaseInRegulatoryLiabilities102.90.00.037.6-23.448.5-69.1-96.8-12.618.6-77.333.0-10.10.00.028.4

us-gaap:InterestPaidNet



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value6473626962755165545453535151445144504053404941494143384047
Percentage of InterestPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value40273522363128322827282728272227222718291825192519211919
Percentage of InterestPaidNet63.037.857.431.957.241.155.848.852.051.253.151.354.852.650.653.050.853.445.556.145.852.246.052.746.648.550.048.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value21282229222919272123222421232223212322232219231923232323
Percentage of InterestPaidNet33.039.135.841.835.839.036.942.539.743.641.545.142.346.049.046.449.247.056.244.856.238.856.738.756.053.860.658.5

us-gaap:LongTermPurchaseCommitmentAmount



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-30
Value1218-97-241351-30-4-52227810733-117238716263-382213-2338-62283-7815
Percentage of LongTermPurchaseCommitmentAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossNetOfTax



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value000-101000000000000000000000
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.00.0100.0100.0100.0100.0100.00.0100.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.0100.00.0

us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value000-10100
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.00.0100.0100.0100.0100.0100.0

us-gaap:OtherCostAndExpenseOperating



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value16218517317218117714815816218316914515216814814414517315101121133230417810869403338
Percentage of OtherCostAndExpenseOperating100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherNoncashIncomeExpense



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-5-220-471000-2314-13-327-44151117-186-30-2385731-1
Percentage of OtherNoncashIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value15-14-1410-22170024-17-5-321-200-311-6-12-12-248120-1-2
Percentage of OtherNoncashIncomeExpense-288.7507.1-8.5-10.2100.0-5550.02237.5-2.90.0-179.0514.7-193.1-40.8-47.8-137.5-1.8-18.2-62.6-100.0344.4-12500.0103.4103.530.431.919.4-72.2153.8

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value15332211334180-1-2-144410-6470-631210-4
Percentage of OtherNoncashIncomeExpense-292.5-132.115.5-5.719.82825.0487.5-14.331.8-131.223.5-48.3-34.231.230.342.961.936.370.0-200.0900.026.243.526.829.236.122.2330.8

us-gaap:PaymentsForProceedsFromOtherInvestingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value131815131213731464612440-19022-357303140-32
Percentage of PaymentsForProceedsFromOtherInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value101613161313109106778555-12721-158665545
Percentage of PaymentsForProceedsFromOtherInvestingActivities76.590.483.5120.3114.998.5134.6319.475.0106.2195.0102.971.9104.2145.05200.063.07600.092.156.2111.8120.0200.0857.1144.738.5-960.0-136.8

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value1111127766511120786666064321020-10
Percentage of PaymentsForProceedsFromOtherInvestingActivities85.359.477.853.662.846.685.9171.083.6186.220.0108.866.1131.2165.06700.0-32.8600.027.2-128.158.837.135.3114.368.42.7380.013.2

us-gaap:PaymentsOfDividendsCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value9385848483787877777272717166666666626262605656565652494743
Percentage of PaymentsOfDividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value594242414242414241393938393737383835353435353535353129
Percentage of PaymentsOfDividendsCommonStock63.449.349.749.850.253.453.454.554.153.953.754.354.756.856.957.057.356.356.456.157.761.962.162.161.960.559.5

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value42363536363534353531313131333333333131313129292929292827
Percentage of PaymentsOfDividendsCommonStock45.342.342.442.843.044.544.545.445.243.343.444.044.150.750.650.550.850.851.151.052.452.452.752.752.655.756.358.8

us-gaap:PaymentsToAcquireOtherProductiveAssets



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value10301722321714
Percentage of PaymentsToAcquireOtherProductiveAssets100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivables



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
Value1221571307253268-2342872842957159214
Percentage of ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value1221571307253268-2342872842957159214
Percentage of ProceedsFromCollectionOfRetainedInterestInSecuritizedReceivables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

us-gaap:ProceedsFromContributionsFromParent

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-31
Value10025001001951001300100010001252504065010000303030300
Percentage of ProceedsFromContributionsFromParent100.0100.00.00.0100.0100.0100.0100.00.0100.00.0100.00.0100.0100.00.0100.0100.00.0100.00.00.0100.0100.0100.0100.00.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302016-12-31
Value252510000050150504060
Percentage of ProceedsFromContributionsFromParent25.0100.00.00.00.00.050.0115.450.00.048.0

us-gaap:StatementEquityComponents, dei:LegalEntity

us-gaap:AdditionalPaidInCapital, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value1002500100195100130
Percentage of ProceedsFromContributionsFromParent100.0100.00.00.0100.0100.0100.0100.0

us-gaap:AdditionalPaidInCapital, lnt:Wpl



Period End2020-03-312019-12-312019-09-302018-12-312018-09-302018-06-30
Value2525100050150
Percentage of ProceedsFromContributionsFromParent25.0100.00.00.050.0115.4

us-gaap:ProceedsFromIssuanceOfCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value22820412465459193665667655171220000
Percentage of ProceedsFromIssuanceOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

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
Value228204124654591936
Percentage of ProceedsFromIssuanceOfCommonStock100.0100.0100.0100.0100.0100.099.9100.0100.0

us-gaap:SubsidiarySaleOfStock

us-gaap:ForwardContracts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value222199119048
Percentage of ProceedsFromIssuanceOfCommonStock97.297.195.40.087.9

us-gaap:DebtInstrument, us-gaap:LongtermDebtType, dei:LegalEntity

us-gaap:ProceedsFromIssuanceOfDebt

lnt:TermLoanCreditAgreementThroughMarchTwoThousandTwentyTwo, lnt:TermLoanCreditAgreement, lnt:AlliantEnergyFinanceLLC



Period End2020-03-31
Value300
Percentage of ProceedsFromIssuanceOfDebt100.0

us-gaap:DebtInstrument, us-gaap:LongtermDebtType, us-gaap:SubsequentEventType, dei:LegalEntity

lnt:ThreePointSixFivePercentDebenturesDueTwoThousandFifty, lnt:Debentures, us-gaap:SubsequentEvent, lnt:Wpl



Period End2020-04-30
Value350
Percentage of ProceedsFromIssuanceOfDebt0.0

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-312010-03-31
Value-7-11-1-2616-3423-185-2616-18-17-114-12-238-2015-35111159145-4
Percentage of ProceedsFromPaymentsForOtherFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value2-101-2317-3221-114-2420-230-814-16304-2218-301960-500
Percentage of ProceedsFromPaymentsForOtherFinancingActivities-31.691.3-61.187.5102.494.090.461.887.593.2126.8128.70.6725.098.6133.6-130.816.753.0109.8120.985.8175.255.20.0-61.70.01.8

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-03-312012-03-312011-03-31
Value-2-3-3-4-3-300-1-8-30-510-4-42-2910-3-1-1024-40-4
Percentage of ProceedsFromPaymentsForOtherFinancingActivities26.632.2194.415.5-19.99.2-1.7-3.2-33.930.7-22.61.733.9-841.7-32.232.0-96.2-819.414.5-3.9-22.24.6-94.721.680.4-45.70.0-83.9

us-gaap:Range, dei:LegalEntity

us-gaap:ProceedsFromSaleAndCollectionOfReceivables

srt:Maximum, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value960103251080110116
Percentage of ProceedsFromSaleAndCollectionOfReceivables100.00.0100.0100.0100.00.0100.0100.0

srt:WeightedAverage, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value23-74528133652
Percentage of ProceedsFromSaleAndCollectionOfReceivables24.60.044.110.475.00.033.145.1

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value232721182523181814139101718151513119869889875543223553
Percentage of PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value9141071513119764614151312108765766654321111112
Percentage of PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions42.655.049.343.262.258.458.554.749.748.549.060.484.186.887.379.178.075.475.377.977.981.179.571.465.968.267.167.936.235.439.546.459.345.222.043.6

lnt:Wpl



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
Value1312111099787644222322211112322133211133
Percentage of PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions57.445.050.756.837.841.641.545.350.351.551.039.615.913.212.720.922.024.624.722.122.118.920.528.634.131.832.932.163.864.660.553.640.754.878.056.4

us-gaap:RegulatedAndUnregulatedOperatingRevenue



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value915990790987928816916906
Percentage of RegulatedAndUnregulatedOperatingRevenue100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value518496596441555494547474525472527420450434516411458398504382489431476411528463494383477393497360398404484374477417534389454
Percentage of RegulatedAndUnregulatedOperatingRevenue56.70.060.255.856.20.059.058.257.40.058.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value375362372326415369370330381374370334393352397334375330382324397359354324410355360319369345376315354344374326388348369312392
Percentage of RegulatedAndUnregulatedOperatingRevenue41.00.037.641.342.10.039.940.541.70.040.80.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:PublicUtilityRegulatedOrUnregulatedStatus, us-gaap:StatementBusinessSegments

us-gaap:UnregulatedOperation, us-gaap:AllOtherSegments



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-03-31
Value212122161010891010119911101112131311141113131211
Percentage of RegulatedAndUnregulatedOperatingRevenue2.42.22.91.71.11.31.01.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments

lnt:Electric



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value730915691743704861726708695840680677666864675668623835640671622771643675798612633815612572796620842
Percentage of RegulatedAndUnregulatedOperatingRevenue79.892.587.575.30.092.789.077.30.092.70.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

lnt:Gas



Period End2020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value15241652151474468185138456215410639571529338511981524776240397319746501674622946
Percentage of RegulatedAndUnregulatedOperatingRevenue16.64.28.321.90.04.88.420.30.05.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

lnt:OtherUtility



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value1113111011111210131311111113912131313141615121522171717121313151615
Percentage of RegulatedAndUnregulatedOperatingRevenue1.30.01.11.41.10.01.31.31.40.01.20.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

lnt:UtilityBusiness



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-03-312010-09-30
Value894859968767970863918805907846897755843786913745834729887706886790830736939855703847874676753859866904
Percentage of RegulatedAndUnregulatedOperatingRevenue97.60.097.897.198.30.098.998.799.00.099.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:StatementBusinessSegments, dei:LegalEntity

lnt:Electric, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value424560392419509422
Percentage of RegulatedAndUnregulatedOperatingRevenue46.456.649.642.554.851.7

lnt:Electric, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value305355298323352304
Percentage of RegulatedAndUnregulatedOperatingRevenue33.435.937.832.837.937.3

lnt:Gas, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value8324381242642
Percentage of RegulatedAndUnregulatedOperatingRevenue9.12.54.912.62.95.2

lnt:Gas, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value691626911826
Percentage of RegulatedAndUnregulatedOperatingRevenue7.61.73.49.21.93.2

lnt:OtherUtility, lnt:Ipl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value111010101110
Percentage of RegulatedAndUnregulatedOperatingRevenue1.21.11.31.11.31.3

lnt:OtherUtility, lnt:Wpl



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value500000.0400000.0400000.0400000.0600000.0200000.0
Percentage of RegulatedAndUnregulatedOperatingRevenue0.10.00.10.00.10.0

us-gaap:RegulatedOperatingRevenueElectricNonNuclear



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value730713915691743704861726708695840
Percentage of RegulatedOperatingRevenueElectricNonNuclear100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value424408560392419394509422405381489
Percentage of RegulatedOperatingRevenueElectricNonNuclear58.257.261.256.856.556.059.158.157.254.858.2

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value305304355298323310352304303314351
Percentage of RegulatedOperatingRevenueElectricNonNuclear41.842.838.843.243.544.040.941.942.845.241.8

us-gaap:RegulatedOperatingRevenueGas



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1521324165215147446818513845
Percentage of RegulatedOperatingRevenueGas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value837624381248926421087827
Percentage of RegulatedOperatingRevenueGas54.557.659.858.957.760.459.661.558.257.059.8

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value6956162691581826775918
Percentage of RegulatedOperatingRevenueGas45.542.440.241.142.339.640.438.541.843.040.2

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
Value1113111011111210131311
Percentage of RegulatedOperatingRevenueOther100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1112101010101110121211
Percentage of RegulatedOperatingRevenueOther95.791.796.496.396.491.595.198.190.992.498.2

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value01000100110
Percentage of RegulatedOperatingRevenueOther4.38.33.63.73.68.54.91.99.17.61.8

us-gaap:CounterpartyName, us-gaap:RelatedPartyTransaction, us-gaap:RelatedPartyTransactionsByRelatedParty

us-gaap:RelatedPartyTransactionAmountsOfTransaction

lnt:AmericanTransmissionCompanyLlcAtc, lnt:AtcBillingsToWpl, us-gaap:EquityMethodInvestee



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-30
Value282827272626272627262827
Percentage of RelatedPartyTransactionAmountsOfTransaction100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:AmericanTransmissionCompanyLlcAtc, lnt:WplBillingsToAtc, us-gaap:EquityMethodInvestee



Period End2020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-30
Value333433223343
Percentage of RelatedPartyTransactionAmountsOfTransaction10.710.711.114.811.511.57.47.711.111.514.311.1

us-gaap:CounterpartyName, us-gaap:RelatedPartyTransaction, us-gaap:RelatedPartyTransactionsByRelatedParty, dei:LegalEntity

lnt:CorporateServices, lnt:AdministrativeandGeneralServicesBillings, us-gaap:SubsidiaryOfCommonParent, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value3748474743424344
Percentage of RelatedPartyTransactionAmountsOfTransaction132.10.0167.9174.1159.30.0165.4169.2

lnt:CorporateServices, lnt:AdministrativeandGeneralServicesBillings, us-gaap:SubsidiaryOfCommonParent, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value3238363533323334
Percentage of RelatedPartyTransactionAmountsOfTransaction114.30.0128.6129.6122.20.0126.9130.8

lnt:CorporateServices, lnt:TransmissionPurchasesBilled, us-gaap:SubsidiaryOfCommonParent, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value8180937484909580
Percentage of RelatedPartyTransactionAmountsOfTransaction289.30.0332.1274.1311.10.0365.4307.7

lnt:CorporateServices, lnt:TransmissionPurchasesBilled, us-gaap:SubsidiaryOfCommonParent, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value2029322930251920
Percentage of RelatedPartyTransactionAmountsOfTransaction71.40.0114.3107.4111.10.073.176.9

lnt:CorporateServices, lnt:TransmissionSalesCredited, us-gaap:SubsidiaryOfCommonParent, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value1518231215141118
Percentage of RelatedPartyTransactionAmountsOfTransaction53.60.082.144.455.60.042.369.2

lnt:CorporateServices, lnt:TransmissionSalesCredited, us-gaap:SubsidiaryOfCommonParent, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value212311278
Percentage of RelatedPartyTransactionAmountsOfTransaction7.10.07.111.13.70.026.930.8

us-gaap:AwardType

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue

lnt:PerformanceRestrictedStockUnit



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312017-03-312016-12-312016-09-302016-06-302016-03-31
Value59.570.00.469999999999998860.045.6339.110.00.0-33.8899999999999967.85
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue100.00.0100.00.0100.0100.00.00.0100.0100.0

us-gaap:PerformanceShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value64.040.00.87999999999999550.046.35
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue107.50.0187.20.0101.6

us-gaap:RestrictedStockUnitsRSU



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value59.570.00.34999999999999430.045.63
Percentage of ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue100.00.074.50.0100.0

us-gaap:ShortTermDebtWeightedAverageInterestRateOverTime



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.018-0.00099999999999999740.0250.0270.0270.00099999999999999740.0220.022
Percentage of ShortTermDebtWeightedAverageInterestRateOverTime100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.0180.00.00.00.0280.00.00.023
Percentage of ShortTermDebtWeightedAverageInterestRateOverTime100.0-0.00.00.0103.70.00.0104.5

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value0.018-0.00100000000000000090.0230.0250.0250.00200000000000000180.020.018
Percentage of ShortTermDebtWeightedAverageInterestRateOverTime100.0100.092.092.692.6200.090.981.8

us-gaap:ShorttermDebtAverageOutstandingAmount



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-06-30
Value382-223995314981380234310-29386307276-31220213199412293127-263072622752281911701331006622855129
Percentage of ShorttermDebtAverageOutstandingAmount100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value000000050001000000000000000417121181068
Percentage of ShorttermDebtAverageOutstandingAmount0.00.40.00.00.1-1.40.02.20.0-0.00.10.30.0-0.00.00.00.00.00.40.10.00.40.10.00.10.00.12.81.07.519.365.463.82.20.052.8

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-06-30
Value167-92714113810234511-262171347943637252000-34157141173140125721114130145577
Percentage of ShorttermDebtAverageOutstandingAmount43.740.46.826.627.772.528.619.33.787.856.243.828.6-15.516.517.613.046.80.00.00.0133.151.454.062.861.665.742.78.914.819.70.049.5100.059.8

us-gaap:ShorttermDebtMaximumAmountOutstandingDuringPeriod



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-06-30
Value462047159060001534463360424397325324822924201811521510353311316284223243185162102229496264
Percentage of ShorttermDebtMaximumAmountOutstandingDuringPeriod100.00.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value000050190313020149031001891038610062619303518541211133
Percentage of ShorttermDebtMaximumAmountOutstandingDuringPeriod0.20.00.00.08.40.00.07.00.90.04.73.72.80.01.20.70.00.010.26.40.90.010.71.93.20.02.710.810.518.634.481.457.712.50.050.4

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-06-30
Value21208919319516751093602712121135555625524000018516820416515916035353204496152
Percentage of ShorttermDebtMaximumAmountOutstandingDuringPeriod45.80.019.032.832.50.049.224.510.90.063.953.434.91457.922.327.423.00.00.00.00.00.052.354.064.758.271.465.719.221.931.80.047.0100.057.6

us-gaap:SubsidiarySaleOfStock

us-gaap:StockIssuedDuringPeriodSharesNewIssues

us-gaap:ForwardContracts



Period End2020-03-312019-12-312019-09-302019-06-302019-03-31
Value44201
Percentage of StockIssuedDuringPeriodSharesNewIssues100.0100.0100.00.0100.0

us-gaap:StockholdersEquityOther



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0-4-3-20-1-1-10
Percentage of StockholdersEquityOther100.0100.0100.0100.00.0100.0100.0100.0100.0

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
Value0-4-3-20-20-20
Percentage of StockholdersEquityOther200.095.5105.7114.30.0117.6-5.6117.6100.0

us-gaap:DeferredCompensationShareBasedPayments



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value000000-10
Percentage of StockholdersEquityOther-100.04.5-5.7-14.30.0-17.6105.6-17.6

us-gaap:TaxesExcludingIncomeAndExciseTaxes



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value27262727292626242726272526252525262525262625252426242326232425252526242525
Percentage of TaxesExcludingIncomeAndExciseTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value141414151614141113131413131313131313131414131312131313131313131313131213
Percentage of TaxesExcludingIncomeAndExciseTaxes53.654.753.355.156.754.053.247.551.552.553.351.850.853.053.752.052.153.453.954.053.254.253.553.552.953.858.453.354.953.952.652.051.650.652.152.0

lnt:Wpl



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
Value1111121111111112121111111211111111101011111010101110811910111110111010
Percentage of TaxesExcludingIncomeAndExciseTaxes42.443.043.841.740.643.743.549.644.443.843.744.745.543.842.544.844.143.442.642.643.042.342.644.042.942.637.843.341.842.944.743.342.642.942.642.0

us-gaap:UnregulatedOperatingRevenue



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value21212122161010108991010101199101110111312131311141113131216211879473942
Percentage of UnregulatedOperatingRevenue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:UtilitiesOperatingExpenseFuelUsed



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value184175218164218215227208
Percentage of UtilitiesOperatingExpenseFuelUsed100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value1069512683128115122116
Percentage of UtilitiesOperatingExpenseFuelUsed57.754.658.050.559.053.453.856.1

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-30
Value777991818910010591
Percentage of UtilitiesOperatingExpenseFuelUsed42.345.442.049.541.046.646.243.9

us-gaap:UtilitiesOperatingExpenseGasAndPetroleumPurchased



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value85709201218211271117515
Percentage of UtilitiesOperatingExpenseGasAndPetroleumPurchased100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value4439510634561660419
Percentage of UtilitiesOperatingExpenseGasAndPetroleumPurchased52.056.564.852.952.155.756.661.154.554.066.0

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value403039583641050345
Percentage of UtilitiesOperatingExpenseGasAndPetroleumPurchased48.043.535.247.147.944.343.438.945.546.034.0

dei:LegalEntity

us-gaap:UtilitiesOperatingExpenseMaintenanceAndOperations

lnt:Ipl



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
Value86991009710810594971051151048994103949392102941009210289929790839086838684100968691
Percentage of UtilitiesOperatingExpenseMaintenanceAndOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:Wpl



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
Value547262626368546256696656576254505267575654776668636564595854636268635660
Percentage of UtilitiesOperatingExpenseMaintenanceAndOperations62.673.462.264.158.865.257.364.253.460.263.363.360.160.357.254.756.666.160.456.458.376.474.574.565.672.776.966.067.564.672.673.568.166.165.065.6

dei:EntityCommonStockSharesOutstanding



Period End2020-03-312020-01-312019-09-302019-06-302019-03-312019-01-312018-09-302018-06-302018-03-312018-01-312017-09-302017-06-302017-03-312017-01-312016-09-302016-06-302016-03-312016-01-292015-09-302015-06-302015-03-312015-01-302014-09-302014-06-302014-03-312014-01-312013-09-302013-06-302013-03-312013-01-312012-09-302012-06-30
Value249245240237237236235233231231231231227227227227113113113113112110110110110110110110110110110110
Percentage of EntityCommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:AllowanceForDoubtfulAccountsReceivableSold

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value116899
Percentage of AllowanceForDoubtfulAccountsReceivableSold100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:CashProceedsFromReceivablesSold

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value162715108
Percentage of CashProceedsFromReceivablesSold100.0100.0100.0100.0100.0

lnt:CommonStockHeldInTrustShares



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value360852.0381232.0385343.0380863.0375542.0384580.0377723.0465450.0458639.0463365.0454532.0450173.0440704.0441695.0432619.0430964.0214881.0215093.0210647.0206419.0232550.0238935.0234836.0229489.0224076.0227469.0222415.0217404.0212456.0216030.0261057.0255319.0249298.0262735.0259247.0258405.0251729.0246301.0262161.0
Percentage of CommonStockHeldInTrustShares100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

lnt:CommonStockHeldInTrustWeightedAverageValuePerShare



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value27.4426.2426.5226.2225.9325.625.2724.4724.1723.9123.5223.2522.8922.7122.5422.2540.3639.6939.2838.8238.2737.4536.9436.4435.8935.2534.8734.4834.0733.6132.6832.3732.131.6831.4731.2131.030.7530.25
Percentage of CommonStockHeldInTrustWeightedAverageValuePerShare100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:CustomerAccountsReceivableSoldAmount

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value131124154138140
Percentage of CustomerAccountsReceivableSoldAmount100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:DeferredProceedsOfReceivablesSold

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value199194245224129
Percentage of DeferredProceedsOfReceivablesSold100.0100.0100.0100.0100.0

us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value188187237214178119243208120222115170149211239172
Percentage of DeferredProceedsOfReceivablesSold94.496.796.595.70.092.30.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueByMeasurementBasis, dei:LegalEntity

us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value188187237214119
Percentage of DeferredProceedsOfReceivablesSold94.496.796.595.792.3

lnt:FairValueOfDeferredProceedsOfReceivablesSold



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-312015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-31
Value1881872372141781192432081202221151701492112391721171771601931702038669122663253
Percentage of FairValueOfDeferredProceedsOfReceivablesSold100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-312015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value188187237214178119243208120222115170149211239172117177160193170203866912266153813253
Percentage of FairValueOfDeferredProceedsOfReceivablesSold100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value188187237214119
Percentage of FairValueOfDeferredProceedsOfReceivablesSold100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:FairValueInputsLevel3



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-31
Value18818723721417811924320812022211517014921123974154172195731171771601931702038669122663253
Percentage of FairValueOfDeferredProceedsOfReceivablesSold100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity

us-gaap:FairValueInputsLevel3, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value188187237214119
Percentage of FairValueOfDeferredProceedsOfReceivablesSold100.0100.0100.0100.0100.0

lnt:InvestmentsBusinessLine1



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value319320309302295293285283275274339335327317309303302293296293288286285281276272268264259257253247242238237233231227218
Percentage of InvestmentsBusinessLine1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:OtherReceivablesSoldAmount

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value900000.0900000.0400000.0400000.0100000.0
Percentage of OtherReceivablesSoldAmount100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:ReceivablesSold

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value215221246229237
Percentage of ReceivablesSold100.0100.0100.0100.0100.0

us-gaap:AccountsNotesLoansAndFinancingReceivableByReceivableType, dei:LegalEntity

lnt:UnbilledUtilityRevenuesSoldAmount

us-gaap:FinanceReceivables, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value8395929097
Percentage of UnbilledUtilityRevenuesSoldAmount100.0100.0100.0100.0100.0

dei:LegalEntity

us-gaap:AccountsPayableRelatedPartiesCurrent

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-312018-03-312017-12-312017-09-302016-12-312016-09-302015-12-31
Value4939404328355056435537
Percentage of AccountsPayableRelatedPartiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AccountsReceivableGrossCurrent



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value10091911031119388
Percentage of AccountsReceivableGrossCurrent100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value0000040
Percentage of AccountsReceivableGrossCurrent0.00.00.00.00.04.90.0

lnt:Wpl



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-31
Value908384971048181
Percentage of AccountsReceivableGrossCurrent89.991.293.294.693.586.991.8

us-gaap:PublicUtility

us-gaap:AccrualForEnvironmentalLossContingencies

us-gaap:NaturalGasProcessingPlant



Period End2020-03-312019-12-312019-09-302019-06-30
Value16181919
Percentage of AccrualForEnvironmentalLossContingencies100.0100.0100.0100.0

us-gaap:PublicUtility, dei:LegalEntity

us-gaap:NaturalGasProcessingPlant, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-30
Value13151616
Percentage of AccrualForEnvironmentalLossContingencies81.283.384.284.2

us-gaap:AdditionalPaidInCapitalCommonStock



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value267424452236210821002045203819471851184518381830169916931686168116731663165616491631150915081507150615071506150615041511151215111510151015091509150715061499
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value2447234723222322232222222027192717971797169716971597159714721447144714071342134212421242124212121182115211221092106210371007977927927873903974
Percentage of AdditionalPaidInCapitalCommonStock91.596.0103.8110.2110.6108.799.599.097.197.492.492.894.094.487.486.186.584.781.181.476.282.482.480.578.576.574.572.670.668.766.664.761.461.457.959.864.6

lnt:Wpl



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
Value14591434140913091309130913091259110911091059101910191019959959959959959959959959959959959959959959959959869869869869869869844
Percentage of AdditionalPaidInCapitalCommonStock54.658.663.062.162.364.064.264.759.960.157.655.760.060.256.957.057.357.757.958.258.863.563.663.663.763.663.663.763.863.557.557.557.657.557.657.656.0

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value97101284544
Percentage of AllowanceForDoubtfulAccountsReceivableCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value113110000
Percentage of AllowanceForDoubtfulAccountsReceivableCurrent11.116.429.510.812.612.57.814.617.5

lnt:Wpl



Period End2020-03-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-31
Value8671073411
Percentage of AllowanceForDoubtfulAccountsReceivableCurrent88.983.670.589.281.677.182.435.445.0

us-gaap:AssetRetirementObligation



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value2241961972032041771841952142162142141951841121141281271261091061061021019781829190817675716563
Percentage of AssetRetirementObligation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302009-12-31
Value161133135143144118134124135137134132122107505165646447474746454546475656474443434341
Percentage of AssetRetirementObligation72.068.268.670.470.866.672.763.763.363.862.762.162.558.344.345.450.850.850.843.744.544.244.944.847.256.557.561.761.958.657.757.461.265.866.2

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations



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
Value581719917417252471228331512151311
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value259185661223656774547
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations42.752.592.83.738.848.695.444.223.021.248.739.333.332.164.3

lnt:Wpl



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
Value2249164497452435463
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations38.724.94.894.426.436.13.138.320.971.423.045.132.052.727.7

us-gaap:CommercialPaper



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-03-312010-12-312009-12-31
Value8033734939051444113682336320390368302244238220213159109120411413533072212792372232432177016257102223247190
Percentage of CommercialPaper100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-06-302010-12-31
Value016800138105382630252242129152114525190000146158155183143148160860352325047
Percentage of CommercialPaper0.049.90.00.026.923.928.132.09.17.857.557.730.121.45.020.811.912.50.00.00.00.041.551.370.365.760.466.765.739.80.021.940.925.00.0100.0

us-gaap:CommonStockHeldInTrust



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value9101010999111111101010109988888888887777888888777
Percentage of CommonStockHeldInTrust100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DeferredCosts



Period End2020-03-312019-12-31
Value5972
Percentage of DeferredCosts100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-31
Value2831
Percentage of DeferredCosts47.643.9

lnt:Wpl



Period End2020-03-312019-12-31
Value2323
Percentage of DeferredCosts38.731.9

us-gaap:DeferredCreditsAndOtherLiabilities



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
Value3692370837473834388137493702367936803646403539303886383437833733369936893765378136513624341532843218
Percentage of DeferredCreditsAndOtherLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



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
Value2025202720292140215220211989199820122012235222702228218021822147212821252168220521242123202419271882
Percentage of DeferredCreditsAndOtherLiabilities54.954.754.255.855.553.953.754.354.755.258.357.857.356.957.757.557.557.657.658.358.258.659.358.758.5

lnt:Wpl



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
Value1632166916981679172217231711167816701645165816371634162917341665164516321653162815831562144214111386
Percentage of DeferredCreditsAndOtherLiabilities44.245.045.343.844.446.046.245.645.445.141.141.742.142.545.944.644.544.243.943.143.443.142.243.043.1

us-gaap:DeferredIncomeTaxLiabilitiesNet



Period End2020-03-312019-12-31
Value17361714
Percentage of DeferredIncomeTaxLiabilitiesNet100.0100.0

dei:LegalEntity

lnt:Ipl



Period End2020-03-312019-12-31
Value10101008
Percentage of DeferredIncomeTaxLiabilitiesNet58.258.8

lnt:Wpl



Period End2020-03-312019-12-31
Value647626
Percentage of DeferredIncomeTaxLiabilitiesNet37.336.5

us-gaap:StatementScenario, us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear

srt:ScenarioForecast, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit



Period End2020-12-31
Value8
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear100.0

srt:ScenarioForecast, us-gaap:PensionPlansDefinedBenefit



Period End2020-12-31
Value59
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear738.3

us-gaap:StatementScenario, us-gaap:RetirementPlanType, dei:LegalEntity

srt:ScenarioForecast, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Ipl



Period End2020-12-31
Value1
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear22.2

srt:ScenarioForecast, us-gaap:OtherPostretirementBenefitPlansDefinedBenefit, lnt:Wpl



Period End2020-12-31
Value6
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear74.1

srt:ScenarioForecast, us-gaap:PensionPlansDefinedBenefit, lnt:Ipl



Period End2020-12-31
Value19
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear239.5

srt:ScenarioForecast, us-gaap:PensionPlansDefinedBenefit, lnt:Wpl



Period End2020-12-31
Value21
Percentage of DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear269.1

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeAssets

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-312015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value1826302121284831142529371341271816388311941263660232610152416
Percentage of DerivativeAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value1622231317
Percentage of DerivativeAssets88.283.276.963.562.5

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value247810
Percentage of DerivativeAssets11.816.823.136.537.5

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value44881581654421141312232261011431314443710
Percentage of DerivativeAssets21.417.926.737.473.331.434.417.429.116.39.92.912.811.16.80.00.013.60.00.013.06.77.68.927.117.68.722.661.018.347.121.731.262.1

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel3



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value1422221351931261021263611362533615173214367610830223346921512176
Percentage of DerivativeAssets78.682.173.362.626.768.665.682.670.983.790.197.187.288.993.20.00.086.40.00.087.093.392.491.172.982.491.377.439.081.752.978.368.837.9

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel2, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value22444
Percentage of DerivativeAssets13.410.415.818.714.1

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel2, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value12344
Percentage of DerivativeAssets8.07.510.918.717.3

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel3, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value141918913
Percentage of DerivativeAssets74.972.861.144.748.4

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel3, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value02335
Percentage of DerivativeAssets3.79.312.217.820.1

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

us-gaap:CommodityContract, us-gaap:CarryingReportedAmountFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value18263021212848311425293713412718
Percentage of DerivativeAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis, dei:LegalEntity

us-gaap:CommodityContract, us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value1622231317
Percentage of DerivativeAssets88.283.276.963.562.5

us-gaap:CommodityContract, us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value247810
Percentage of DerivativeAssets11.816.823.136.537.5

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeAssetsCurrent

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value10151818152439281021263512292531615193493063963125345117235122214
Percentage of DerivativeAssetsCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value812121216
Percentage of DerivativeAssetsCurrent82.276.668.865.265.4

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value13568
Percentage of DerivativeAssetsCurrent17.823.431.234.834.6

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeAssetsNoncurrent

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value811113538334221122513007819229129624321
Percentage of DerivativeAssetsNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value8101011
Percentage of DerivativeAssetsNoncurrent95.392.789.754.343.2

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value00112
Percentage of DerivativeAssetsNoncurrent4.77.310.345.756.8

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeLiabilities

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-312015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value51373128152322424641454545283664423714139202737174083785267
Percentage of DerivativeLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2217131211
Percentage of DerivativeLiabilities43.846.342.143.648.1

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2820181512
Percentage of DerivativeLiabilities56.253.757.956.451.9

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel2



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value503631271016145781417003411161615141956231032123062644763
Percentage of DerivativeLiabilities99.097.998.498.265.669.166.813.815.620.433.039.21.81.78.40.00.024.80.00.034.951.939.745.931.115.439.588.474.976.575.283.190.395.1

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel3



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value00005773639333027442833337248423127188761716449201353
Percentage of DerivativeLiabilities1.02.11.61.834.430.933.286.284.479.667.060.898.298.391.60.00.075.20.00.065.148.160.354.168.984.660.511.625.123.524.816.99.74.9

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByFairValueHierarchyLevel, dei:LegalEntity

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel2, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value211612116
Percentage of DerivativeLiabilities42.944.140.641.827.9

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel2, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value282018159
Percentage of DerivativeLiabilities56.253.757.956.441.2

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel3, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value00004
Percentage of DerivativeLiabilities1.02.11.61.820.2

us-gaap:CommodityContract, us-gaap:FairValueInputsLevel3, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value00002
Percentage of DerivativeLiabilities0.00.00.00.010.7

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis

us-gaap:CommodityContract, us-gaap:CarryingReportedAmountFairValueDisclosure



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302015-12-31
Value51373128152322424641454545283664
Percentage of DerivativeLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, us-gaap:FairValueByMeasurementBasis, dei:LegalEntity

us-gaap:CommodityContract, us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2217131211
Percentage of DerivativeLiabilities43.846.342.143.648.1

us-gaap:CommodityContract, us-gaap:CarryingReportedAmountFairValueDisclosure, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value2820181512
Percentage of DerivativeLiabilities56.253.757.956.451.9

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeLiabilitiesCurrent

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value2919131235711151818171313212356473527242897461121133161554155
Percentage of DerivativeLiabilitiesCurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value128553
Percentage of DerivativeLiabilitiesCurrent42.546.841.845.055.4

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value1710772
Percentage of DerivativeLiabilitiesCurrent57.553.258.255.044.6

us-gaap:DerivativeInstrumentRisk

us-gaap:DerivativeLiabilitiesNoncurrent

us-gaap:CommodityContract



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-03-312011-12-312011-09-302010-12-31
Value21181815121714313023262731151513271723191895541415153921221112
Percentage of DerivativeLiabilitiesNoncurrent100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DerivativeInstrumentRisk, dei:LegalEntity

us-gaap:CommodityContract, lnt:Ipl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value98768
Percentage of DerivativeLiabilitiesNoncurrent45.845.742.442.445.8

us-gaap:CommodityContract, lnt:Wpl



Period End2020-03-312019-12-312019-09-302019-06-302018-12-31
Value11101089
Percentage of DerivativeLiabilitiesNoncurrent54.254.357.657.654.2

us-gaap:Energy, us-gaap:TradingActivityByType

us-gaap:DerivativeNonmonetaryNotionalAmount

srt:NaturalGasPerThousandCubicFeet, us-gaap:Commodity



Period End2020-03-312019-12-312019-09-30
Value185189184
Percentage of DerivativeNonmonetaryNotionalAmount100.0100.0100.0

us-gaap:Energy, us-gaap:TradingActivityByType, dei:LegalEntity

srt:NaturalGasPerThousandCubicFeet, us-gaap:Commodity, lnt:Ipl



Period End2020-03-312019-12-312019-09-30
Value106102101
Percentage of DerivativeNonmonetaryNotionalAmount57.354.355.2

srt:NaturalGasPerThousandCubicFeet, us-gaap:Commodity, lnt:Wpl



Period End2020-03-312019-12-312019-09-30
Value798682
Percentage of DerivativeNonmonetaryNotionalAmount42.745.744.8

us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized



Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value125710134811145810145
Percentage of EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

dei:LegalEntity

lnt:Ipl



<
Period End2020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value73