SO


Line plots across dimensions of each concept
Line plots across concepts
Tables

Table of contents



us-gaap:CommonStockValue
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:SharesIssued
us-gaap:StatementEquityComponents
dei:LegalEntity
us-gaap:CommonStockSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:ComprehensiveIncomeNetOfTax
dei:LegalEntity

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest
dei:LegalEntity

us-gaap:CostOfGoodsAndServicesSold
dei:LegalEntity, us-gaap:ProductOrService
dei:LegalEntity, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService

us-gaap:CostsAndExpenses
dei:LegalEntity

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal
dei:LegalEntity
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:PublicUtility

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
dei:LegalEntity

us-gaap:IncomeTaxExpenseBenefit
dei:LegalEntity

us-gaap:IncomeTaxesPaidNet
dei:LegalEntity

us-gaap:InterestAndDebtExpense
dei:LegalEntity

us-gaap:InterestPaidNet
dei:LegalEntity

us-gaap:NetIncomeLoss
dei:LegalEntity
dei:LegalEntity, us-gaap:ConsolidationItems
dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest
dei:LegalEntity

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic
dei:LegalEntity
dei:LegalEntity, us-gaap:ConsolidationItems
dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService

us-gaap:NonoperatingIncomeExpense
dei:LegalEntity

us-gaap:OperatingIncomeLoss
dei:LegalEntity
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

us-gaap:OtherComprehensiveIncomeLossNetOfTax
dei:LegalEntity

us-gaap:OtherNonoperatingIncomeExpense
dei:LegalEntity

us-gaap:PreferredStockDividendsIncomeStatementImpact
dei:LegalEntity

us-gaap:ProfitLoss
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

us-gaap:Revenues
dei:LegalEntity
dei:LegalEntity, us-gaap:ConsolidationItems
dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
dei:LegalEntity, us-gaap:ProductOrService
dei:LegalEntity, us-gaap:StatementBusinessSegments
dei:LegalEntity, us-gaap:StatementBusinessSegments, us-gaap:Subsegments
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:ProductOrService
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
us-gaap:StatementBusinessSegments

us-gaap:Assets
dei:LegalEntity
dei:LegalEntity, us-gaap:ConsolidatedEntities, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
dei:LegalEntity, us-gaap:ConsolidationItems
dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:ProductOrService
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService

us-gaap:Liabilities
dei:LegalEntity
dei:LegalEntity, us-gaap:ConsolidatedEntities, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

us-gaap:LiabilitiesAndStockholdersEquity
dei:LegalEntity

us-gaap:StockholdersEquity
dei:LegalEntity

us-gaap:AssetsCurrent
dei:LegalEntity

us-gaap:CashAndCashEquivalentsAtCarryingValue
dei:LegalEntity

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents
dei:LegalEntity
dei:LegalEntity
us-gaap:InventoryNet

us-gaap:OtherAssetsCurrent
dei:LegalEntity

us-gaap:PropertyPlantAndEquipmentGross
dei:LegalEntity

us-gaap:ConstructionInProgressGross
dei:LegalEntity
dei:LegalEntity, us-gaap:BusinessAcquisition
dei:LegalEntity, us-gaap:PublicUtility

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
dei:LegalEntity
dei:LegalEntity, us-gaap:PropertyPlantAndEquipmentByType
us-gaap:PropertyPlantAndEquipmentByType

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

us-gaap:PropertyPlantAndEquipmentNet
dei:LegalEntity

us-gaap:LongTermInvestments
dei:LegalEntity

us-gaap:Goodwill
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:UnusualOrInfrequentItem

us-gaap:IntangibleAssetsNetExcludingGoodwill
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsNet
dei:LegalEntity
dei:LegalEntity, us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
dei:LegalEntity
us-gaap:IntangibleAssetsNetIncludingGoodwill
dei:LegalEntity
us-gaap:DeferredTaxAssetsLiabilitiesNet

us-gaap:OperatingLeaseRightOfUseAsset
dei:LegalEntity

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

us-gaap:AccountsPayableCurrent

us-gaap:AccruedIncomeTaxesCurrent
dei:LegalEntity

us-gaap:LiabilitiesCurrent
dei:LegalEntity

us-gaap:OperatingLeaseLiabilityCurrent
dei:LegalEntity

us-gaap:OtherLiabilitiesCurrent
dei:LegalEntity
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity
us-gaap:TaxesPayableCurrent

us-gaap:LongTermDebtAndCapitalLeaseObligations
dei:LegalEntity

us-gaap:DeferredIncomeTaxLiabilitiesNet
dei:LegalEntity

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

us-gaap:MinorityInterest
dei:LegalEntity

us-gaap:OtherLiabilitiesNoncurrent
dei:LegalEntity

us-gaap:OperatingLeaseLiabilityNoncurrent
dei:LegalEntity

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo
dei:LegalEntity

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree
dei:LegalEntity

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour
dei:LegalEntity

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive
dei:LegalEntity

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive
dei:LegalEntity

us-gaap:OperatingLeaseLiability
dei:LegalEntity
dei:LegalEntity, us-gaap:PropertyPlantAndEquipmentByType, us-gaap:RelatedPartyTransactionsByRelatedParty

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue
dei:LegalEntity

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount
dei:LegalEntity

us-gaap:StockholdersEquity
dei:LegalEntity

us-gaap:StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest
dei:LegalEntity
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType, us-gaap:StatementEquityComponents
dei:LegalEntity, us-gaap:RetirementPlanType, us-gaap:StatementEquityComponents
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType, us-gaap:StatementEquityComponents
us-gaap:RetirementPlanType, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue
dei:LegalEntity

us-gaap:AdditionalPaidInCapitalCommonStock
dei:LegalEntity

us-gaap:RetainedEarningsAccumulatedDeficit
dei:LegalEntity

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
dei:LegalEntity

us-gaap:TreasuryStockValue

us-gaap:MinorityInterest
dei:LegalEntity

us-gaap:StockIssuedDuringPeriodValueNewIssues
us-gaap:StatementEquityComponents

us-gaap:AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue
us-gaap:StatementEquityComponents

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

us-gaap:NetCashProvidedByUsedInOperatingActivities
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInInvestingActivities
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInFinancingActivities
dei:LegalEntity

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect
dei:LegalEntity

us-gaap:DeferredIncomeTaxExpenseBenefit
dei:LegalEntity

us-gaap:IncreaseDecreaseInAccountsPayable
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInOperatingActivities
dei:LegalEntity

us-gaap:NetIncomeLoss
dei:LegalEntity
dei:LegalEntity, us-gaap:ConsolidationItems
dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:ConsolidationItems
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService

us-gaap:ProfitLoss
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

us-gaap:NetCashProvidedByUsedInInvestingActivities
dei:LegalEntity

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment
dei:LegalEntity

us-gaap:NetCashProvidedByUsedInFinancingActivities
dei:LegalEntity

us-gaap:ProceedsFromIssuanceOfLongTermDebt

us-gaap:RepaymentsOfLongTermDebt

us-gaap:PaymentsOfDividendsCommonStock
dei:LegalEntity

us-gaap:EffectiveIncomeTaxRateContinuingOperations
dei:LegalEntity

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice

us-gaap:DeferredTaxLiabilities
dei:LegalEntity

us-gaap:DeferredTaxAssetsNet
dei:LegalEntity

us-gaap:UnrecognizedTaxBenefits

us-gaap:DeferredTaxAssetsValuationAllowance
dei:LegalEntity
dei:LegalEntity, so:CostCategory, us-gaap:PublicUtility
so:AdditionalConstructionCapitalCosts
dei:LegalEntity, so:CostCategory, us-gaap:PublicUtility
so:AdditionalConstructionCapitalCostsThreshold
dei:LegalEntity, so:CostCategory, us-gaap:Range, us-gaap:PublicUtility
dei:LegalEntity
so:AmortizationOfDeferredInvestmentTaxCredits

so:AmortizationofOtherIntangibleAssetsRecordedasaReductiontoOperatingRevenues
dei:LegalEntity
so:CapitalContributionsFromToParentCompany
dei:LegalEntity, us-gaap:StatementEquityComponents

so:ChangeInConstructionPayables
dei:LegalEntity
us-gaap:SubsequentEventType
so:CommonStockConversionPrice
dei:LegalEntity, us-gaap:PublicUtility
so:ConstructionFinancingCosts
dei:LegalEntity
so:CurrentBillingRatesUnderRateECRAnnualDecreaseAmount
dei:LegalEntity
so:CurrentBillingRatesUnderRateECRPercentageDecrease
dei:LegalEntity, us-gaap:StatementScenario
so:CurrentBillingRatesUnderRateECRinTermsofPerUnits
dei:LegalEntity, so:VogtleConstructionMonitoringReportNumber, us-gaap:PublicUtility
so:CustomerRefund

so:DepreciationAndAmortizationExcludingNuclearFuel
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtility
so:DisposalGroupNotDiscontinuedOperationGainLossOnDisposalNetOfTax
dei:LegalEntity, us-gaap:ConsolidatedEntities, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
so:DistributionMadeToLimitedPartnerCashDistributionsPaidPercentage
dei:LegalEntity, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteBaseProjectCapitalCostForecastMonthly

so:EstimatedLossOnPlantVogtleUnits3And4
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity
so:EstimatedLossOnPlantVogtleUnits3And4NetOfTax
dei:LegalEntity, us-gaap:PublicUtility

so:EstimatedLossOnPlantVogtleUnits3And4NonCashAdjusted
dei:LegalEntity

so:ExpectedVolumeOfNaturalGasSubjectToOptionToSellBackExcessGasDueToOperationalConstraints
dei:LegalEntity
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
so:GainLossOnDispositionOfPropertyPlantEquipmentNetOfTax

so:IncreaseDecreaseInAccruedTaxes
dei:LegalEntity

so:IncreaseDecreaseInCustomerRefunds
dei:LegalEntity

so:IncreaseDecreaseInNaturalGasCostUnderRecoveryCurrentPortion
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtility
so:IncreaseDecreaseInTariff

so:IncreaseDecreaseRetailFuelCostOverRecoveryShortTerm
dei:LegalEntity

so:IncreaseDecreaseinEnergyRelatedInventoryNaturalGasinStorage
dei:LegalEntity

so:IncreaseDecreaseinFairValueofFundsIncludingReinvestedInterestandDividends
dei:LegalEntity

so:LeaseImpairmentLoss
us-gaap:StatementBusinessSegments

so:LeaseImpairmentLossAfterTax
us-gaap:StatementBusinessSegments
dei:LegalEntity, us-gaap:StatementScenario
so:LiabilityForClaimsAndClaimsAdjustmentExpenseAnnualRecoveryAmount
dei:LegalEntity, us-gaap:StatementScenario
so:NaturalDisasterReserveExpectedRecoveryAmount

so:NaturalGasCostUnderRecoveryLongTerm
dei:LegalEntity

so:NetIncomeLossIncludingPortionAttributableToNoncontrollingInterestNetofPreferredStockDividends
us-gaap:StatementEquityComponents

so:NoncashOrPartNoncashTransactionContributionsFromNoncontrollingInterests
dei:LegalEntity

so:NoncontrollingInterestIncreasefromContributionsfromNoncontrollingInterestHolders
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
so:NotionalAmountofInterestRateDerivativesInterestRatePaid
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:VariableRate

so:PaymentsPursuantToLongTermServiceAgreements
dei:LegalEntity
dei:LegalEntity, so:CostCategory, us-gaap:CounterpartyName, us-gaap:PublicUtility
so:PercentageOfConstructionCostsResponsibilityToPay
dei:LegalEntity, so:CostCategory, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:PublicUtility
so:PercentageOfCostsDisallowedForRecovery
dei:LegalEntity
so:ProceedsFromFederalFinancingBankLoan
dei:LegalEntity, us-gaap:PublicUtility
so:ProceedsfromRecoveryofFinancingCosts
dei:LegalEntity, us-gaap:PublicUtility
so:ProductionTaxCreditsAggregatePurchasePriceMaximum
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesAllowanceforFundsUsedDuringConstructionMonthly
dei:LegalEntity
so:PublicUtilitiesApprovedRateIncreaseDecreaseAmountRecoveryOfInvestments
dei:LegalEntity
so:PublicUtilitiesIncreaseDecreaseInIncrementalCOVID19CostsDeferred
dei:LegalEntity
so:PublicUtilitiesInfrastructureReplacementProgramsAndCapitalProjectsExpenditures
dei:LegalEntity, so:Program
dei:LegalEntity, so:ConstructionMonitoringReportNumber, us-gaap:PublicUtility
so:PublicUtilitiesRequestedCapitalConstructionCosts
dei:LegalEntity, so:ConstructionMonitoringReportNumber, us-gaap:StatementScenario, us-gaap:PublicUtility
dei:LegalEntity, so:VogtleConstructionMonitoringReportNumber, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesRequestedFinancingCostsDeferredAmount
dei:LegalEntity
so:PublicUtilitiesRequestedRateIncreaseAdValoremTaxesPreviouslyRecoveredThroughPerformanceEvaluationPlanAmount
dei:LegalEntity, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:SubsequentEventType
so:PublicUtilitiesRequestedRateIncreaseDecreaseAmountRecoveryOfInvestments
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesRequestedRateIncreaseDecreaseAnnualAmount

so:PurchaseOfMembershipInterestsFromNoncontrollingInterests
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
dei:LegalEntity
so:RepaymentsOfFederalFinancingBankLoan
dei:LegalEntity
so:ReturnOfPaidInCapital
dei:LegalEntity, us-gaap:StatementEquityComponents
dei:LegalEntity
so:RightOfUseAssetObtainedInExchangeForOperatingAndFinanceLeaseLiability
dei:LegalEntity
so:TransferOfConstructionWorkInProgressToLeaseReceivables
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:AmortizationOfRegulatoryAsset

us-gaap:AssetRetirementObligationAccretionExpense
dei:LegalEntity

us-gaap:AssetRetirementObligationCashPaidToSettle
dei:LegalEntity

us-gaap:AssetRetirementObligationLiabilitiesIncurred
dei:LegalEntity

us-gaap:AssetRetirementObligationLiabilitiesSettled
dei:LegalEntity
dei:LegalEntity
us-gaap:AssetRetirementObligationPeriodIncreaseDecrease

us-gaap:AssetRetirementObligationRevisionOfEstimate
dei:LegalEntity

us-gaap:CapitalExpendituresIncurredButNotYetPaid
dei:LegalEntity

us-gaap:ContractWithCustomerLiabilityRevenueRecognized

us-gaap:ContributionOfProperty
dei:LegalEntity
dei:LegalEntity, 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:DefinedBenefitPlanServiceCost
us-gaap:RetirementPlanType

us-gaap:DepreciationAmortizationAndAccretionNet
dei:LegalEntity
dei:LegalEntity
us-gaap:DerivativeGainLossOnDerivativeNet
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation
us-gaap:DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet
us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation, us-gaap:IncomeStatementLocation

us-gaap:DividendsCommonStockCash
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents
dei:LegalEntity
us-gaap:ExciseTaxesCollected
dei:LegalEntity
us-gaap:FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationGainLossIncludedInEarnings
dei:LegalEntity
us-gaap:FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationSettlements
dei:LegalEntity
us-gaap:FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersIntoLevel3
dei:LegalEntity
us-gaap:FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputsReconciliationTransfersOutOfLevel3

us-gaap:GainLossOnDispositionOfAssets1
dei:LegalEntity
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:GainLossOnSaleOfPropertyPlantEquipment

us-gaap:IncomeLossFromEquityMethodInvestments
dei:LegalEntity
dei:LegalEntity, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
dei:LegalEntity, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:IncomeLossFromIndividuallySignificantComponentDisposedOfOrHeldForSaleExcludingDiscontinuedOperationsAttributableToParentBeforeIncomeTax

us-gaap:IncreaseDecreaseInAccruedSalaries
dei:LegalEntity
dei:LegalEntity
us-gaap:IncreaseDecreaseInContractWithCustomerLiability
dei:LegalEntity
us-gaap:IncreaseDecreaseInFossilFuelInventories

us-gaap:IncreaseDecreaseInInterestPayableNet

us-gaap:IncreaseDecreaseInMaterialsAndSupplies
dei:LegalEntity

us-gaap:IncreaseDecreaseInOtherOperatingAssets
dei:LegalEntity

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities
dei:LegalEntity

us-gaap:IncreaseDecreaseInPrepaidExpense
dei:LegalEntity
dei:LegalEntity
us-gaap:IncreaseDecreaseInPrepaidTaxes

us-gaap:IncreaseDecreaseInReceivables
dei:LegalEntity

us-gaap:IncrementalCommonSharesAttributableToShareBasedPaymentArrangements

us-gaap:InterestPaidCapitalized
dei:LegalEntity

us-gaap:InvestmentTaxCredit
dei:LegalEntity

us-gaap:LeaseIncome
dei:LegalEntity
dei:LegalEntity
us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpensePeriodIncreaseDecrease
dei:LegalEntity, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent
dei:LegalEntity, us-gaap:LitigationCase, us-gaap:LitigationStatus
us-gaap:LossContingencyDamagesSoughtValue

us-gaap:OperatingLeaseLeaseIncome
dei:LegalEntity

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

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax
dei:LegalEntity

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationTax
dei:LegalEntity

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax
dei:LegalEntity
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation
us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationBeforeTax
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship, us-gaap:IncomeStatementLocation

us-gaap:OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationTax
dei:LegalEntity

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

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax
dei:LegalEntity

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax
dei:LegalEntity

us-gaap:OtherNoncashIncomeExpense
dei:LegalEntity

us-gaap:PaymentsForProceedsFromOtherInvestingActivities
dei:LegalEntity

us-gaap:PaymentsForRemovalCosts
dei:LegalEntity
dei:LegalEntity
us-gaap:PaymentsOfCapitalDistribution

us-gaap:PaymentsToAcquireBusinessesNetOfCashAcquired
dei:LegalEntity

us-gaap:PaymentsToAcquireEquityMethodInvestments
dei:LegalEntity

us-gaap:PaymentsToInvestInDecommissioningFund
dei:LegalEntity

us-gaap:PaymentsToMinorityShareholders
dei:LegalEntity

us-gaap:PensionAndOtherPostretirementBenefitExpense
dei:LegalEntity
dei:LegalEntity
us-gaap:ProceedsFromContributionsFromParent

us-gaap:ProceedsFromDecommissioningFund
dei:LegalEntity
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:ProceedsFromDivestitureOfBusinesses

us-gaap:ProceedsFromIssuanceOfCommonStock
dei:LegalEntity
us-gaap:ProceedsFromIssuanceOfFirstMortgageBond
dei:LegalEntity
us-gaap:ProceedsFromIssuanceOfOtherLongTermDebt
dei:LegalEntity
us-gaap:ProceedsFromIssuanceOfSeniorLongTermDebt
dei:LegalEntity, us-gaap:CreditFacility
us-gaap:ProceedsFromLinesOfCredit

us-gaap:ProceedsFromMinorityShareholders
dei:LegalEntity

us-gaap:ProceedsFromNotesPayable
dei:LegalEntity

us-gaap:ProceedsFromOtherShortTermDebt
dei:LegalEntity
dei:LegalEntity, us-gaap:AssetAcquisition
us-gaap:ProceedsFromPartnershipContribution
dei:LegalEntity, us-gaap:BusinessAcquisition
dei:LegalEntity, us-gaap:Ownership, us-gaap:BusinessAcquisition
dei:LegalEntity, us-gaap:SubsequentEventType

us-gaap:ProceedsFromPaymentsForOtherFinancingActivities
dei:LegalEntity
dei:LegalEntity
us-gaap:ProceedsFromPollutionControlBond

us-gaap:ProceedsFromSaleOfProductiveAssets
dei:LegalEntity

us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtility
us-gaap:PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedInterest
dei:LegalEntity
us-gaap:PublicUtilitiesApprovedRateIncreaseDecreaseAmount
dei:LegalEntity, us-gaap:ProductOrService, us-gaap:StatementScenario
dei:LegalEntity, us-gaap:ProductOrService, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:PublicUtilitiesRegulatoryProceeding
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:SubsequentEventType
dei:LegalEntity
us-gaap:PublicUtilitiesApprovedRateIncreaseDecreasePercentage
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:StatementScenario
us-gaap:PublicUtilitiesApprovedReturnOnEquityPercentage
dei:LegalEntity, us-gaap:StatementScenario, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:SubsequentEventType
us-gaap:PublicUtilitiesRequestedEquityCapitalStructurePercentage
dei:LegalEntity
us-gaap:PublicUtilitiesRequestedRateIncreaseDecreaseAmount
dei:LegalEntity, us-gaap:PublicUtilitiesRegulatoryProceeding, us-gaap:SubsequentEventType
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:SubsequentEventType
dei:LegalEntity
us-gaap:PublicUtilitiesRequestedRateIncreaseDecreasePercentage
dei:LegalEntity, us-gaap:SubsequentEventType
us-gaap:PublicUtilitiesRequestedReturnOnEquityPercentage
dei:LegalEntity
us-gaap:RepaymentsOfMediumTermNotes

us-gaap:RepaymentsOfNotesPayable
dei:LegalEntity

us-gaap:RepaymentsOfOtherShortTermDebt
dei:LegalEntity
dei:LegalEntity
us-gaap:RepaymentsOfPollutionControlBond
dei:LegalEntity
us-gaap:RepaymentsOfSeniorDebt
dei:LegalEntity, us-gaap:ProductOrService
us-gaap:RevenueNotFromContractWithCustomer
us-gaap:ProductOrService

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability
dei:LegalEntity

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability
dei:LegalEntity

us-gaap:SalesTypeLeaseInterestIncome
dei:LegalEntity
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodSharesNewIssues

us-gaap:StockOptionPlanExpense

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

us-gaap:StormDamageProvision
dei:LegalEntity

us-gaap:TaxesExcludingIncomeAndExciseTaxes
dei:LegalEntity

us-gaap:UtilitiesOperatingExpenseMaintenanceAndOperations
dei:LegalEntity

us-gaap:VariableLeaseIncome
dei:LegalEntity

so:AccumulatedDeferredTaxAssets
dei:LegalEntity

so:AccumulatedDeferredTaxLiabilities
dei:LegalEntity
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:PublicUtility
so:AccumulatedProvisionsForDecommissioning
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:AccumulatedReserveBalanceForFutureStorms
dei:LegalEntity
so:AdjustingPointOfWeightedCostOfEquity
dei:LegalEntity, us-gaap:PublicUtility
so:AllowanceForFundsUsedDuringConstructionCapitalizedInterestAccrued

so:AmountOfVariableRatePollutionControlRevenueBondsOutstandingRequiringLiquiditySupport
dei:LegalEntity
dei:LegalEntity
so:AmountofFixedRatePollutionControlRevenueBondsOutstandingRequiringLiquiditySupport
dei:LegalEntity, us-gaap:StatementClassOfStock
so:AnnualDividendPreferredAndPreferenceStock
dei:LegalEntity, us-gaap:AssetAcquisition
so:ApproximateNameplateCapacity
dei:LegalEntity, us-gaap:BusinessAcquisition
dei:LegalEntity, us-gaap:StatementScenario, us-gaap:BusinessAcquisition

so:BankCreditArrangementsNoTermLoanDueWithInOneYear
dei:LegalEntity
dei:LegalEntity, us-gaap:CounterpartyName
so:CogenerationAssetsNet
dei:LegalEntity
so:CompositeRateUsedForAllowanceForFundsUsedDuringConstruction
dei:LegalEntity
so:ContractWithCustomerLiabilityBillCredits

so:CustomerDepositsCurrent1
dei:LegalEntity

so:DecommissioningFundInvestmentsNetOfReceivables
dei:LegalEntity
dei:LegalEntity, us-gaap:FinancialInstrument
us-gaap:FinancialInstrument

so:DeferredChargesAndOtherAssets
dei:LegalEntity
dei:LegalEntity, us-gaap:PropertyPlantAndEquipmentByType
dei:LegalEntity, us-gaap:RegulatoryAsset
us-gaap:PropertyPlantAndEquipmentByType

so:DeferredChargesRelatedToIncomeTaxes
dei:LegalEntity

so:DeferredCreditsRelatedToIncomeTaxes
dei:LegalEntity
dei:LegalEntity
so:DeferredUnderRecoveredRegulatoryClauseRevenues
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
so:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeRegulatoryAmortization
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
so:DerivativeCumulativeAmountofFairValueHedgingAdjustmentIncludedinCarryingAmount
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:HedgingDesignation, us-gaap:Position
so:DerivativeNonmonetaryNotionalAmountNetLongShortPositionVolume
dei:LegalEntity
so:DerivativeNotionalAmountReceive
us-gaap:DisposalGroupClassification
so:DisposalGroupIncludingDiscontinuedOperationLeveragedLeases
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
so:DisposalGroupIncludingDiscontinuedOperationNetBookValueExcludingWorkingCapital
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
so:DisposalGroupNotDiscontinuedOperationContingentMilestonePaymentAmount

so:ElectricUtilityPlantinService
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteAdditionalConstructionContingencyEstimateSubjectToRateRecoveryEvaluation
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteAmountInExcessOfInitialConstructionContingencyEstimate
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteBaseProjectCapitalCostForecast
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteConstructionContingencyEstimateFinancingCosts
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteConstructionContingencyEstimateFinancingCostsIncurredToDate

so:EstimatedCostToCompleteConstructionContingencyEstimateSubjectToRateRecoveryEvaluation
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCostToCompleteCostsNotSharedWithOtherOwners
dei:LegalEntity, us-gaap:PublicUtility
so:EstimatedCosttoCompleteConstructionContingencyEstimate
dei:LegalEntity, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
dei:LegalEntity, us-gaap:Range, us-gaap:BusinessAcquisition
so:EstimatedFutureConstructionPayments
dei:LegalEntity
so:FairMarketValueOfFundsSecuritiesOnLoanUnderFundsManagersSecuritiesLendingProgram
dei:LegalEntity
so:FairValueGainLoss
dei:LegalEntity, so:HedgingMaturityDate, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeInstrumentRisk
us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
dei:LegalEntity
so:FairValueOfCollateralReceivedAmount
dei:LegalEntity, us-gaap:PublicUtility
so:GuaranteeObligationsofContractorsParent
dei:LegalEntity
so:HeaderImprovementProjectScopeOfProject
dei:LegalEntity, us-gaap:RegulatoryAsset
so:IncrementalRestorationCosts
dei:LegalEntity, us-gaap:Range
so:IntegratedCapacityDeliveryPlanCapitalForecastPlanAmountYearsOneThroughTen
dei:LegalEntity, us-gaap:Range, us-gaap:SubsequentEventType
dei:LegalEntity
so:JointOwnerAccountsReceivable
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant
so:JointlyOwnedUtilityPlantFutureMinimumPaymentsReceivable

so:LeaseLiability
dei:LegalEntity
dei:LegalEntity, us-gaap:PropertyPlantAndEquipmentByType
us-gaap:PropertyPlantAndEquipmentByType
dei:LegalEntity
so:LesseeOperatingLeaseLeaseNotYetCommencedLiability
so:LeveragedLeases
so:LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureUnearnedIncome

so:LineOfCreditExpireRemainderOfFiscalYear
dei:LegalEntity

so:LineOfCreditExpireYearFive
dei:LegalEntity

so:LineOfCreditExpireYearFour
dei:LegalEntity

so:LineOfCreditExpireYearOne
dei:LegalEntity

so:LineOfCreditExpireYearThree
dei:LegalEntity
dei:LegalEntity, us-gaap:CreditFacility

so:LineOfCreditExpireYearTwo
dei:LegalEntity
dei:LegalEntity, us-gaap:CreditFacility
so:LineOfCreditFacilityRemainingBorrowingCapacityYearOne
dei:LegalEntity, us-gaap:CreditFacility
so:LineOfCreditFacilityRemainingBorrowingCapacityYearThree
dei:LegalEntity
so:LongTermDebtMaturityYearThreeIntendedToBePaidInYearOne
dei:LegalEntity
so:LongTermDebtMaturityYearTwentyIntendedToBePaidInYearOne

so:LongTermDebtandFinanceLeaseObligationNet
dei:LegalEntity
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:RelatedPartyTransactionsByRelatedParty
so:LongTermPurchaseCommitmentReimbursementPercentage
dei:LegalEntity, us-gaap:CounterpartyName
so:MRATariffTermsCounterpartysOptionToReduceUseOfServicesCumulativeAnnualAmount
dei:LegalEntity, us-gaap:CounterpartyName
so:MRATariffTermsCounterpartysOptionToReduceUseOfServicesMaximumTotalReductionPercentage
dei:LegalEntity
so:MinimumNaturalDisasterReserveBalanceTriggeringEstablishmentCharge
dei:LegalEntity
so:MotionFiledToWithdrawProjectApplicationHeaderImprovementProjectScopeOfProject
dei:LegalEntity, us-gaap:SubsequentEventType
dei:LegalEntity
so:NaturalDisasterReserve
dei:LegalEntity, us-gaap:StatementScenario
so:NaturalDisasterReserveAuthorizedLimit
dei:LegalEntity
so:NaturalGasPipelineCapacityEnergy
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk
so:NetQuantityPurchaseOfDerivativesNotDesignatedAsHedges
us-gaap:DerivativeInstrumentRisk
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
so:NonQualifiedDeferredCompensationTrustsFairValueDisclosure
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

so:NuclearFuelAtAmortizedCost
dei:LegalEntity

so:OperatingLeaseLiabilityIncludingHeldForSale

so:OtherAccountsNotesAndLoansReceivable
dei:LegalEntity

so:OtherCostOfRemovalObligations
dei:LegalEntity

so:OtherRegulatoryAssetsCurrent
dei:LegalEntity
dei:LegalEntity, us-gaap:RegulatoryAsset

so:OtherRegulatoryAssetsDeferred
dei:LegalEntity
dei:LegalEntity, us-gaap:RegulatoryAsset
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity
so:OtherRegulatoryAssetsUnderRecoveredEnvironmentalCostCurrent
dei:LegalEntity
so:OtherRegulatoryAssetsUnderRecoveredEnvironmentalCostsDeferred

so:OtherRegulatoryLiabilitiesCurrent
dei:LegalEntity

so:OtherRegulatoryLiabilitiesDeferred
dei:LegalEntity
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity
so:OverRecoveredFuelBalance
dei:LegalEntity, us-gaap:ProductOrService
so:OverRecoveredFuelCost
dei:LegalEntity
so:OverRecoveredRegulatoryClauseLiabilities
dei:LegalEntity
so:OverUnderRecoveredEnvironmentalClause
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:OverUnderRecoveredFuelBalance
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity
so:OverUnderRecoveredFuelCost
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:OverUnderRecoveredNaturalGasBalance
dei:LegalEntity
so:PSCRetailRateIncreaseDecrease
dei:LegalEntity
so:PercentOfBasisPoints
dei:LegalEntity, us-gaap:StatementScenario
dei:LegalEntity, us-gaap:Range, us-gaap:MeasurementInputType
so:PerformanceEvaluationPlanMeasurementInput

so:PlantInServiceNetOfDepreciation
dei:LegalEntity
dei:LegalEntity
so:PortionOfActualEarningsAboveApprovedROEBandRefundedToCustomersValue
dei:LegalEntity, us-gaap:StatementScenario
dei:LegalEntity
so:PowerPurchaseAgreementAdditionalGeneratingCapacity
dei:LegalEntity, us-gaap:PublicUtility
so:PreliminaryEstimatedCosttoComplete
dei:LegalEntity
so:PrepaidLongTermServiceAgreements
dei:LegalEntity, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent
so:PropertyDamageReserve
dei:LegalEntity, us-gaap:StatementOperatingActivitiesSegment
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesApprovedAdditionalGeneratingCapacityConstruction
dei:LegalEntity
so:PublicUtilitiesApprovedAdditionalGeneratingCapacityDemandsideManagementAndDistributedEnergyResourcePrograms
dei:LegalEntity
so:PublicUtilitiesApprovedAdditionalGeneratingCapacityPurchases
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesEstimatedInServiceCost
dei:LegalEntity
so:PublicUtilitiesIncrementalCOVID19CostsDeferred
dei:LegalEntity
so:PublicUtilitiesIncrementalCOVID19CostsDeferredCreditLossExpense
dei:LegalEntity
so:PublicUtilitiesIncrementalCOVID19CostsDeferredOther
dei:LegalEntity
so:PublicUtilitiesInfrastructureReplacementProgramsAndCapitalProjectsExpendituresSinceProjectInception
dei:LegalEntity, so:Program
dei:LegalEntity
so:PublicUtilitiesInfrastructureReplacementProgramsAndCapitalProjectsPipeInstalledSinceProjectInception
dei:LegalEntity, so:Program
dei:LegalEntity
so:PublicUtilitiesInfrastructureReplacementProgramsAndCapitalProjectsScopeOfProgram
dei:LegalEntity, so:Program

so:PublicUtilitiesPropertyPlantAndEquipmentOther
dei:LegalEntity

so:PublicUtilitiesPropertyPlantandEquipmentGeneral
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesPropertyPlantandEquipmentInvestmentNet

so:PublicUtilitiesPropertyPlantandEquipmentStorageFacilities
dei:LegalEntity

so:PublicUtilitiesPropertyPlantandEquipmentTransportationandDistribution
dei:LegalEntity
dei:LegalEntity, us-gaap:PublicUtilitiesRegulatoryProceeding, us-gaap:SubsequentEventType
so:PublicUtilitiesRequestedRateIncreaseDecreaseAmountDueInNextFiscalYear
dei:LegalEntity, us-gaap:PublicUtility
so:PublicUtilitiesRequiredFossilStreamGenerationRetirements
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:SubsequentEventType
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
so:PurchaseContractAdjustmentLiability
us-gaap:DebtInstrument, us-gaap:LongtermDebtType
so:PurchaseContractAdjustmentLiabilityCurrent
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:RatePowerPurchaseAgreement
dei:LegalEntity
so:RateRSEIncrease
dei:LegalEntity
so:RateRSEIncreaseAmount
dei:LegalEntity
so:RateRSERefundLiability
dei:LegalEntity, us-gaap:StatementScenario
so:RecoveryEstimateOfUnderRecoveredCCRRuleCosts

so:RegulatoryAssetAssetRetirementObligation
dei:LegalEntity

so:RegulatoryAssetAssetRetirementObligationCurrent
dei:LegalEntity
dei:LegalEntity
so:RegulatoryAssetStormDamageReservesCurrent
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:RegulatoryClauseAdValoremTax
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:RegulatoryClausePropertyDamageReserve

so:RequiredCollateralCreditRatingDowngrade
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:RetailEnergyCostRecovery
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant
so:SiteStudyCosts
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:PublicUtility
dei:LegalEntity
so:TemporaryLIFOLiquidationLiabilityCurrent

so:UnamortizedFairValueAdjustmentofLongtermDebt
dei:LegalEntity

so:UnbilledRevenuesCurrent
dei:LegalEntity
dei:LegalEntity
so:UnderRecoveredCertifiedPowerPurchaseAgreements
dei:LegalEntity, us-gaap:BalanceSheetLocation
so:UnderRecoveredRateBalance

so:UtilityPlantInService
dei:LegalEntity

so:WeatherDerivativePremium
dei:LegalEntity
dei:LegalEntity
us-gaap:AccountsPayableOtherCurrent

us-gaap:AccountsReceivableGrossCurrent
dei:LegalEntity

us-gaap:AccountsReceivableNet
dei:LegalEntity
dei:LegalEntity, us-gaap:ConcentrationRiskByBenchmark, us-gaap:ConcentrationRiskByType, us-gaap:StatementBusinessSegments

us-gaap:AccrualForTaxesOtherThanIncomeTaxesCurrent
dei:LegalEntity
dei:LegalEntity
us-gaap:AccruedEnvironmentalLossContingenciesCurrent

us-gaap:AccruedEnvironmentalLossContingenciesNoncurrent
dei:LegalEntity

us-gaap:AccruedSalariesCurrent
dei:LegalEntity

us-gaap:AccumulatedDeferredInvestmentTaxCredit
dei:LegalEntity

us-gaap:AllowanceForDoubtfulAccountsReceivableCurrent
dei:LegalEntity
dei:LegalEntity, us-gaap:FinancialInstrument
us-gaap:AlternativeInvestment
dei:LegalEntity, us-gaap:InvestmentType

us-gaap:AssetRetirementObligation
dei:LegalEntity

us-gaap:AssetRetirementObligationCurrent
dei:LegalEntity

us-gaap:AssetRetirementObligationsNoncurrent
dei:LegalEntity
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:AssetsFairValueDisclosure
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency

us-gaap:AssetsHeldForSaleNotPartOfDisposalGroupCurrent
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperation
us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupClassification, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:AssetsOfDisposalGroupIncludingDiscontinuedOperationCurrent
dei:LegalEntity
us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:BusinessCombinationContingentConsiderationLiability
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency
dei:LegalEntity, us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment
dei:LegalEntity, us-gaap:BusinessAcquisition
us-gaap:BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:CashAndCashEquivalentsFairValueDisclosure
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency

us-gaap:CollateralAlreadyPostedAggregateFairValue
dei:LegalEntity

us-gaap:ContractWithCustomerAssetNet
dei:LegalEntity
us-gaap:ProductOrService

us-gaap:ContractWithCustomerLiability
dei:LegalEntity
us-gaap:ProductOrService

us-gaap:DebtInstrumentCarryingAmount
dei:LegalEntity
dei:LegalEntity, us-gaap:LongtermDebtType
us-gaap:LongtermDebtType
dei:LegalEntity, us-gaap:CreditFacility
us-gaap:DebtInstrumentCollateralAmount

us-gaap:DebtInstrumentFairValue
dei:LegalEntity

us-gaap:DebtInstrumentUnamortizedDiscountPremiumNet
dei:LegalEntity
dei:LegalEntity, us-gaap:LongtermDebtType
us-gaap:DebtWeightedAverageInterestRate
us-gaap:LongtermDebtType

us-gaap:DecommissioningFundInvestments
dei:LegalEntity

us-gaap:DeferredCreditsAndOtherLiabilities
dei:LegalEntity

us-gaap:DeferredGasCost
dei:LegalEntity
dei:LegalEntity, us-gaap:BalanceSheetLocation
dei:LegalEntity
us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DeferredIncomeTaxLiabilities

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsOperatingLossCarryforwardsStateAndLocal
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementGeographical
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedBenefitObligation
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeBeforeTax
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetPriorServiceCostCreditBeforeTax
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:MeasurementInputType, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:MeasurementInputType, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:MeasurementInputType, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
us-gaap:MeasurementInputType, us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanTaxStatus, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanBenefitObligation
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:RetirementPlanTaxStatus, us-gaap:RetirementPlanType
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanFundedStatusOfPlan
us-gaap:RetirementPlanType
so:DefinedBenefitPlanHealthCareCostTrendRateCategory, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanHealthCareCostTrendRateAssumedNextFiscalYear
so:DefinedBenefitPlanHealthCareCostTrendRateCategory, us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanUltimateHealthCareCostTrendRate1
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeAmountOfHedgedItem
us-gaap:BalanceSheetLocation, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship

us-gaap:DerivativeAssetFairValueGrossLiability
dei:LegalEntity
dei:LegalEntity, us-gaap:Range, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FinancialInstrument, us-gaap:MeasurementInputType, us-gaap:ValuationTechnique
us-gaap:DerivativeAssetLiabilityNetMeasurementInput

us-gaap:DerivativeAssets
dei:LegalEntity
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

us-gaap:DerivativeAssetsCurrent
dei:LegalEntity
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FinancialInstrument
us-gaap:DerivativeAssetsLiabilitiesAtFairValueNet

us-gaap:DerivativeFairValueOfDerivativeAsset

us-gaap:DerivativeFairValueOfDerivativeLiability
dei:LegalEntity
us-gaap:DerivativeInstrumentsAndHedgesLiabilities

us-gaap:DerivativeLiabilities
dei:LegalEntity
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument
us-gaap:FairValueByMeasurementFrequency, us-gaap:FinancialInstrument

us-gaap:DerivativeLiabilityFairValueGrossAsset
dei:LegalEntity
dei:LegalEntity, so:HedgingMaturityDate, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeLiabilityNotionalAmount
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeInstrumentRisk
dei:LegalEntity, us-gaap:DerivativeInstrumentRisk, us-gaap:DerivativeInstrumentsGainLossByHedgingRelationship
us-gaap:DerivativeNotionalAmount
us-gaap:DerivativeInstrumentRisk
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationAccountsNotesAndLoansReceivableNet
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationAccountsPayableCurrent
us-gaap:DisposalGroupClassification

us-gaap:DisposalGroupIncludingDiscontinuedOperationCash
dei:LegalEntity
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType
us-gaap:DisposalGroupIncludingDiscontinuedOperationConsideration
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationDeferredTaxAssets
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationInventoryCurrent
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherCurrentAssets
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentAssets
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationOtherNoncurrentLiabilities
us-gaap:DisposalGroupClassification
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipment
us-gaap:DisposalGroupClassification
dei:LegalEntity
us-gaap:DueFromRelatedPartiesCurrent
dei:LegalEntity
us-gaap:DueToRelatedPartiesCurrent
us-gaap:AwardType
us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized

us-gaap:EnergyMarketingContractLiabilitiesCurrent
dei:LegalEntity

us-gaap:EnergyMarketingContractsAssetsCurrent
dei:LegalEntity

us-gaap:EnergyRelatedInventoryNaturalGasInStorage
dei:LegalEntity

us-gaap:EnergyRelatedInventoryOtherFossilFuel
dei:LegalEntity
dei:LegalEntity
us-gaap:EnvironmentalExitCostsAssetsPreviouslyDisposedLiabilityForRemediation
dei:LegalEntity, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:EquityMethodInvestmentOwnershipPercentage

us-gaap:EquityMethodInvestments
dei:LegalEntity
dei:LegalEntity, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
dei:LegalEntity, us-gaap:FinancialInstrument
us-gaap:FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
dei:LegalEntity, us-gaap:InvestmentType
dei:LegalEntity
us-gaap:FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisWithUnobservableInputs

us-gaap:FinanceLeaseLiability
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityCurrent
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityNoncurrent
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDue
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDueAfterYearFive
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDueNextTwelveMonths
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDueYearFive
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDueYearFour
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDueYearThree
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityPaymentsDueYearTwo
dei:LegalEntity

us-gaap:FinanceLeaseLiabilityUndiscountedExcessAmount
dei:LegalEntity

us-gaap:FinanceLeaseRightOfUseAsset
dei:LegalEntity

us-gaap:FinanceLeaseWeightedAverageDiscountRatePercent
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsAccumulatedAmortization
dei:LegalEntity
dei:LegalEntity, us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsByMajorClass

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFive
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearFour
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearThree
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo
dei:LegalEntity

us-gaap:FiniteLivedIntangibleAssetsGross
dei:LegalEntity
dei:LegalEntity, us-gaap:FiniteLivedIntangibleAssetsByMajorClass
us-gaap:FiniteLivedIntangibleAssetsByMajorClass
dei:LegalEntity
us-gaap:ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months
dei:LegalEntity, us-gaap:GainContingenciesByNature
us-gaap:GainContingencyUnrecordedAmount
dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations
us-gaap:GuaranteeObligationsCurrentCarryingValue
dei:LegalEntity
us-gaap:IncomeTaxesReceivableNoncurrent

us-gaap:IntangibleAssetsGrossExcludingGoodwill

us-gaap:InterestPayableCurrent
dei:LegalEntity

us-gaap:InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant
us-gaap:JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:RelatedPartyTransactionsByRelatedParty
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant
us-gaap:JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:RelatedPartyTransactionsByRelatedParty
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant
us-gaap:JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:RelatedPartyTransactionsByRelatedParty
dei:LegalEntity
us-gaap:JointlyOwnedUtilityPlantProportionateOwnershipShare
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant
dei:LegalEntity, us-gaap:JointlyOwnedUtilityPlant, us-gaap:RelatedPartyTransactionsByRelatedParty
dei:LegalEntity, us-gaap:PublicUtility
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:RelatedPartyTransactionsByRelatedParty
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:RelatedPartyTransactionsByRelatedParty, us-gaap:SubsequentEventType
dei:LegalEntity
us-gaap:LIFOInventoryAmount

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceived
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceivedFiveYears
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceivedFourYears
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceivedNextTwelveMonths
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceivedThereafter
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceivedThreeYears
dei:LegalEntity

us-gaap:LessorOperatingLeasePaymentsToBeReceivedTwoYears
dei:LegalEntity
so:LeveragedLeases
us-gaap:LeveragedLeasesBalanceSheetInvestmentInLeveragedLeases

us-gaap:LeveragedLeasesBalanceSheetInvestmentInLeveragedLeasesNet
so:LeveragedLeases
us-gaap:LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureDeferredTaxesArisingFromLeveragedLeases
so:LeveragedLeases
us-gaap:LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureInvestmentInLeveragedLeasesNet
so:LeveragedLeases
us-gaap:LeveragedLeasesNetInvestmentInLeveragedLeasesDisclosureRentalReceivablesNet
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:LiabilitiesFairValueDisclosure
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency
dei:LegalEntity, us-gaap:DisposalGroupClassification
us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation
us-gaap:DisposalGroupClassification
us-gaap:DisposalGroupClassification, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations

us-gaap:LiabilitiesOfDisposalGroupIncludingDiscontinuedOperationCurrent
dei:LegalEntity
dei:LegalEntity
us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent
dei:LegalEntity, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent
dei:LegalEntity, us-gaap:StatementScenario, us-gaap:BalanceSheetLocation, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent

us-gaap:LineOfCreditFacilityRemainingBorrowingCapacity
dei:LegalEntity
dei:LegalEntity, us-gaap:CreditFacility

us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths
dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive
dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour
dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree
dei:LegalEntity

us-gaap:LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo
dei:LegalEntity
dei:LegalEntity, us-gaap:Range, us-gaap:PublicUtility, us-gaap:UnusualOrInfrequentItem
us-gaap:LossContingencyEstimateOfPossibleLoss

us-gaap:NetRegulatoryAssets
dei:LegalEntity, us-gaap:ConsolidatedEntities, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName
us-gaap:NoncontrollingInterestInVariableInterestEntity

us-gaap:OperatingLeaseWeightedAverageDiscountRatePercent
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementGeographical, us-gaap:IncomeTaxAuthority
us-gaap:OperatingLossCarryforwardsValuationAllowance
dei:LegalEntity, us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:OtherAssetsFairValueDisclosure
dei:LegalEntity, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency

us-gaap:OtherInventorySupplies
dei:LegalEntity

us-gaap:OtherLongTermInvestments
dei:LegalEntity
dei:LegalEntity
us-gaap:PreferredStockValueOutstanding

us-gaap:PrepaidExpenseCurrent
dei:LegalEntity
dei:LegalEntity
us-gaap:PrepaidTaxes

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentDistribution
dei:LegalEntity

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentGenerationOrProcessing
dei:LegalEntity

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentOtherPropertyPlantAndEquipment

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentPlantInService
dei:LegalEntity

us-gaap:PublicUtilitiesPropertyPlantAndEquipmentTransmission
dei:LegalEntity
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligation
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueAfterFifthYear
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInFifthYear
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInFourthYear
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInSecondYear
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueInThirdYear
dei:LegalEntity, us-gaap:RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:RecordedUnconditionalPurchaseObligationDueWithinOneYear
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
us-gaap:RegulatoryAssets
dei:LegalEntity, us-gaap:ProductOrService, us-gaap:RegulatoryAsset
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:RegulatoryAsset
dei:LegalEntity, us-gaap:RegulatoryAsset
dei:LegalEntity, us-gaap:RetirementPlanType
us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
dei:LegalEntity, us-gaap:BalanceSheetLocation, us-gaap:RetirementPlanType
us-gaap:RegulatoryLiabilities
dei:LegalEntity, us-gaap:ProductOrService, us-gaap:RegulatoryAsset
dei:LegalEntity, us-gaap:ProductOrService, us-gaap:RegulatoryLiability
dei:LegalEntity, us-gaap:PublicUtility, us-gaap:RegulatoryLiability
dei:LegalEntity, us-gaap:RegulatoryAsset
dei:LegalEntity, us-gaap:RegulatoryLiability
dei:LegalEntity, us-gaap:RestrictedCashAndCashEquivalentsCashAndCashEquivalents
us-gaap:RestrictedCash
us-gaap:RestrictedCashAndCashEquivalentsCashAndCashEquivalents
dei:LegalEntity, us-gaap:RestrictedCashAndCashEquivalentsCashAndCashEquivalents
us-gaap:RestrictedCashAndCashEquivalents
us-gaap:RestrictedCashAndCashEquivalentsCashAndCashEquivalents
dei:LegalEntity
us-gaap:RetainedEarningsUnappropriated

us-gaap:RevenueRemainingPerformanceObligation
dei:LegalEntity
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivable
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceived
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedFiveYears
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedFourYears
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedNextTwelveMonths
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedThereafter
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedThreeYears
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedTwoYears
dei:LegalEntity
us-gaap:SalesTypeAndDirectFinancingLeasesLeaseReceivableUndiscountedExcessAmount
dei:LegalEntity
us-gaap:SalesTypeLeaseLeaseReceivable
dei:LegalEntity, us-gaap:BalanceSheetLocation
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
us-gaap:StatementClassOfStock
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant

us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
dei:LegalEntity

us-gaap:SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
dei:LegalEntity

us-gaap:ShortTermBorrowings
dei:LegalEntity
dei:LegalEntity, us-gaap:RelatedPartyTransactionsByRelatedParty
dei:LegalEntity, us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtType

us-gaap:ShortTermDebtWeightedAverageInterestRate
dei:LegalEntity
dei:LegalEntity, us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtType
dei:LegalEntity, us-gaap:TaxCreditCarryforward
us-gaap:TaxCreditCarryforwardAmount
us-gaap:TaxCreditCarryforward

us-gaap:TemporaryEquityCarryingAmountAttributableToParent
dei:LegalEntity
dei:LegalEntity, us-gaap:StatementClassOfStock, us-gaap:StatementScenario
us-gaap:TemporaryEquityRedemptionPricePerShare
dei:LegalEntity, us-gaap:StatementScenario, us-gaap:StatementClassOfStock

us-gaap:UnamortizedDebtIssuanceExpense
dei:LegalEntity

us-gaap:UnamortizedLossReacquiredDebtNoncurrent
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
dei:LegalEntity, us-gaap:UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchased
us-gaap:UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears
dei:LegalEntity, us-gaap:ValuationAllowancesAndReservesType
us-gaap:ValuationAllowancesAndReservesBalance
us-gaap:ValuationAllowancesAndReservesType

Plots across concepts


IncomeStatement
Other Comprehensive Income Loss Net Of Tax
Expenses
Income Tax Expense Benefit
Balance Sheet
Intangible Assets Net Excluding Goodwill
Assets
Derivative Assets
Current Assets
Other Assets Current
NonCurrent Assets
Intangible Assets Net Excluding Goodwill
PropertyPlantAndEquipmentNet
Accumulated Depreciation Depletion And Amortization Property Plant And Equipment
Liabilities
Derivative Liabilities
Current Liabilities
Accrued Income Taxes Current
Noncurrent Liabilities
Other Liabilities Noncurrent
Stockholders Equity
Accumulated Other Comprehensive Income Loss Net Of Tax
CashFlow
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInOperatingActivities
Increase Decrease In Accounts Payable
NetCashProvidedByUsedInInvestingActivities
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInFinancingActivities
Net Cash Provided By Used In Financing Activities
Shares
Weighted Average Number Of Shares Outstanding Basic
OperatingLeaseLiability
Operating Lease Liability Current
NonoperatingIncomeExpense
Nonoperating Income Expense
LesseeOperatingLeaseLiabilityPaymentsDue
Lessee Operating Lease Liability Payments Due Year Four
FiniteLivedIntangibleAssets
Finite Lived Intangible Assets Accumulated Amortization

Tables

  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:CommonStockValue NANA5268.0NANANA5257.0NANANA5164.05140.05066.05054.05038.05018.04997.04973.04952.04900.04708.04604.04572.0NANANA4539.0NANA4467.04461.04447.04417.04400.04389.04386.04377.04346.04328.04312.04291.04248.04219.0NANANA4101.0NANANA
 us-gaap:CommonStockValue dei:LegalEntity so:MississippiPowerNANA38.0NANANA38.0NANANA38.038.038.038.038.038.038.038.038.038.038.038.038.038.038.038.037.69137.69137.69137.69137.69137.69137.69137.69137.69137.69137.69137.69137.69137.69137.691NA37.691NANANANANANANA
 us-gaap:CommonStockValue dei:LegalEntity so:SouthernCompanyGasNANA9930.0NANANA9697.0NANANANA0.00.00.00.00.00.00.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:SharesIssued dei:LegalEntity,us-gaap:StatementEquityComponents so:AlabamaPower,us-gaap:CommonStock▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄31.031.031.031.031.031.031.031.031.031.031.031.031.031.031.0NANANA31.0NANANA31.0NANANA31.0NANANA31.0NANANA31.0NANANA31.0NANANA31.0NANANA31.0NANANA
 us-gaap:SharesIssued dei:LegalEntity,us-gaap:StatementEquityComponents so:MississippiPower,us-gaap:CommonStock▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄1.01.01.01.01.01.01.01.01.01.01.01.01.01.01.0NANANA1.0NANANA1.0NANANA1.121NANANA1.121NANANA1.121NANANA1.121NANANA1.121NANANA1.121NANANA
 us-gaap:SharesIssued us-gaap:StatementEquityComponents us-gaap:CommonStock█████████▇▇▇▇▇▆▆▆▆▆▆▅▄▄▄▄▄▄▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▁▁▁1060.01060.01058.01057.01057.01057.01054.01050.01046.01041.2881034.7411029.8741015.1221012.5871008.5321004.5211000.342995.453991.213980.798942.37921.645915.073912.271911.724911.596908.502900.514896.631894.073892.733889.849883.947880.441877.803877.25875.361869.235865.664862.448858.151849.598843.814839.146831.148825.024820.152NANANA
 us-gaap:SharesIssued us-gaap:StatementEquityComponents us-gaap:TreasuryStock█████████▇▃██▄▁1.01.01.01.01.01.01.01.01.00.9920.9531.01.00.9620.929NANANA0.819NANANA3.3523.3323.2993.3350.7250.7020.9353.2615.6478.10910.04410.0510.0353.1440.5650.545-0.539-0.519-0.499-0.475-0.474-0.475-0.442-0.488-0.505NANANA
 us-gaap:CommonStockSharesOutstanding dei:LegalEntity so:MississippiPowerNANA1.0NANANA1.121NANANA1.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.121NA1.121NANANANANANANA
us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding █▁1067.01066.0NA1064.01063.01067.0NA1057.01052.01045.0NA1029.01014.01016.0NA1010.01005.01000.0NA975.0940.0922.0NA912.0912.0915.0NANANA893.0NA881.0879.0875.0NA883.0880.0877.0NA868.0862.0853.939NA842.0833.0824.787NANANANA
us-gaap:WeightedAverageNumberOfSharesOutstandingBasic █▁1061.01060.0NA1058.01058.01057.0NA1048.01044.01038.0NA1023.01014.01011.0NA1003.0998.0993.0NA968.0934.0916.0NA910.0909.0910.0NANANA890.0NA878.0874.0870.0NA876.0872.0868.0NA860.0855.0847.51NA836.0828.0822.526NANANANA
us-gaap:EarningsPerShareBasic ▅▆▅▆▅▆▅▆▆█▄▆▄▆▅▆▁▅▄▆▅▅▄▆▅▅▄▆▅▅▅▆▅▄▅▆▅▅▄▆▅▅▄▆▅▅▄▆▅▄0.351.070.37000000000000011.180.580.820.421.260.862.010.271.14-0.150.930.491.07-1.380.660.21.170.650.530.31.050.690.560.310.80.680.390.470.970.340.090.441.110.710.420.31.070.710.50.180.980.620.60.310.990.610.16
us-gaap:EarningsPerShareDiluted ▅▆▅▆▅▆▅▆▆█▄▆▄▆▅▆▁▅▄▆▅▅▄▆▅▅▄▆▅▅▅▆▅▄▅▆▅▅▄▆▅▅▄▆▅▅0.351.060.36000000000000031.180.580.810.421.250.851.990.271.13-0.150.920.491.06-1.370.660.21.160.650.530.31.050.690.560.310.80.680.390.470.970.340.090.441.110.710.420.290000000000000041.060.70.490.169999999999999930.970.610.6NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
 COGS Ratio dei:LegalEntity,us-gaap:ProductOrService so:SouthernCompanyGas,us-gaap:NaturalGasUsRegulated▂█▄▁▂▅▅▁▂▇▄▁▂█▄▁675.01692.01075.0478.0638.01240.01132.0498.0688.01476.01045.0487.0710.01631.01050.0532.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 COGS Ratio us-gaap:ProductOrService us-gaap:NaturalGasUsRegulated▂█▄▁▂▅▅▁▂▇▄▁▂▇▄▁677.01694.01072.0477.0636.01249.01131.0498.0689.01474.01048.0492.0706.01607.01045.0532.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 COGS Ratio us-gaap:ProductOrService us-gaap:ProductAndServiceOther▆▅▆▅▅▅▆▆▅▆▁███▇▆201.0159.0245.0152.0162.0122.0206.0197.0166.0187.0-277.0369.0395.0413.0309.0168.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 Cost Ratio dei:LegalEntity so:AlabamaPower▅▅▃▇▃▃▃█▄▃▂▇▄▄▃▇▄▃▂▇▄▂▁▆▄▃▂▆▃▄▂▅▃▂▂▆▃▁▂▆▄▂▂▆▄1556.01559.01385.01729.01365.01351.01363.01841.01513.01408.01316.01740.01503.01473.01433.01740.01484.01382.01329.01785.01444.01331.01217.01695.01455.01401.01328.01669.01437.01508.01314.01604.01392.01308.01290.01637.01377.01216.01271.01671.01440.01320.01313.01706.01462.0NANANANANA
 Cost Ratio dei:LegalEntity so:GeorgiaPower▅▃▃▇▃▂▁█▄▂▂▇▃▃▂▇▃▂▂▇▄▂▁▇▃▃▃▇▄▅▂▆▃▂▂▆▃▂▂█▅▃▂▇▃2225.01970.01938.02617.01928.01825.01703.02755.02117.01833.01818.02593.02048.01961.01884.02546.02048.01832.01762.02698.02051.01872.01641.02691.02016.01978.01902.02631.02186.02269.01866.02484.02042.01882.01735.02498.02020.01745.01758.02788.02265.01989.01737.02628.02000.0NANANANANA
 Cost Ratio dei:LegalEntity so:MississippiPower▅▅▃▆▄▃▄█▅▄▅▇▄▅▃▇▅▃▃▇▃▂▂▇▃▃▂▇▅▆▃▆▅▂▁▅▃▁▁▆▄▃▂▆▃303.0307.0277.0336.0283.0277.0294.0370.0313.0287.0308.0358.0297.0302.0271.0341.0303.0272.0277.0352.0277.0257.0246.0341.0275.0276.0245.852354.623310.975331.161267.582325.206306.435245.934235.779305.419266.084228.714237.794325.766286.041263.276255.526327.083276.821NANANANANA
 Cost Ratio dei:LegalEntity so:SouthernCompanyGas▂█▄▁▂▅▅▁▂▇▄▁▂█▄▂▂▇▅▁677.01694.01072.0477.0636.01249.01131.0498.0689.01474.01048.0492.0730.01639.01079.0565.0716.01560.01109.0543.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 Cost Ratio dei:LegalEntity so:SouthernPower▅▄▄▆▄▃▄▇▆▅▆█▇▆▅█▆▅▄▆▃▂▂▄▃▃▃▄▂▃▂▃▂▂▂▃▂▁▂▃▂▂▁▃▁490.0440.0396.0523.0439.0375.0411.0574.0510.0443.0506.0635.0555.0509.0478.0618.0529.0450.0389.0500.0373.0315.0304.0401.0337.0348.0386.336435.256328.803350.854300.257364.767307.255302.947291.591354.971285.805253.681286.4362.565305.209281.787268.547356.83248.476NANANANANA
 EBT Margin dei:LegalEntity so:AlabamaPower▅▅▃▇▃▃▃█▄▃▂▇▄▄▃▇▄▃▂▇▄▂▁▆▄▃▂▆▃▄▂▅▃▂▂▆▃▁▂▆▄▂▂▆▄1556.01559.01385.01729.01365.01351.01363.01841.01513.01408.01316.01740.01503.01473.01433.01740.01484.01382.01329.01785.01444.01331.01217.01695.01455.01401.01328.01669.01437.01508.01314.01604.01392.01308.01290.01637.01377.01216.01271.01671.01440.01320.01313.01706.01462.0NANANANANA
 EBT Margin dei:LegalEntity so:GeorgiaPower▅▃▃▇▃▂▁█▄▂▂▇▃▃▂▇▃▂▂▇▄▂▁▇▃▃▃▇▄▅▂▆▃▂▂▆▃▂▂█▅▃▂▇▃2225.01970.01938.02617.01928.01825.01703.02755.02117.01833.01818.02593.02048.01961.01884.02546.02048.01832.01762.02698.02051.01872.01641.02691.02016.01978.01902.02631.02186.02269.01866.02484.02042.01882.01735.02498.02020.01745.01758.02788.02265.01989.01737.02628.02000.0NANANANANA
 EBT Margin dei:LegalEntity so:MississippiPower▅▅▃▆▄▃▄█▅▄▅▇▄▅▃▇▅▃▃▇▃▂▂▇▃▃▂▇▅▆▃▆▅▂▁▅▃▁▁▆▄▃▂▆▃303.0307.0277.0336.0283.0277.0294.0370.0313.0287.0308.0358.0297.0302.0271.0341.0303.0272.0277.0352.0277.0257.0246.0341.0275.0276.0245.852354.623310.975331.161267.582325.206306.435245.934235.779305.419266.084228.714237.794325.766286.041263.276255.526327.083276.821NANANANANA
 EBT Margin dei:LegalEntity so:SouthernCompanyGas▂█▄▁▂▅▅▁▂▇▄▁▂█▄▂▂▇▅▁677.01694.01072.0477.0636.01249.01131.0498.0689.01474.01048.0492.0730.01639.01079.0565.0716.01560.01109.0543.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 EBT Margin dei:LegalEntity so:SouthernPower▅▄▄▆▄▃▄▇▆▅▆█▇▆▅█▆▅▄▆▃▂▂▄▃▃▃▄▂▃▂▃▂▂▂▃▂▁▂▃▂▂▁▃▁490.0440.0396.0523.0439.0375.0411.0574.0510.0443.0506.0635.0555.0509.0478.0618.0529.0450.0389.0500.0373.0315.0304.0401.0337.0348.0386.336435.256328.803350.854300.257364.767307.255302.947291.591354.971285.805253.681286.4362.565305.209281.787268.547356.83248.476NANANANANA
 Net profit Margin dei:LegalEntity so:AlabamaPower▅▅▃▇▃▃▃█▄▃▂▇▄▄▃▇▄▃▂▇▄▂▁▆▄▃▂▆▃▄▂▅▃▂▂▆▃▁▂▆▄▂▂▆▄1556.01559.01385.01729.01365.01351.01363.01841.01513.01408.01316.01740.01503.01473.01433.01740.01484.01382.01329.01785.01444.01331.01217.01695.01455.01401.01328.01669.01437.01508.01314.01604.01392.01308.01290.01637.01377.01216.01271.01671.01440.01320.01313.01706.01462.0NANANANANA
 Net profit Margin dei:LegalEntity so:GeorgiaPower▅▃▃▇▃▂▁█▄▂▂▇▃▃▂▇▃▂▂▇▄▂▁▇▃▃▃▇▄▅▂▆▃▂▂▆▃▂▂█▅▃▂▇▃2225.01970.01938.02617.01928.01825.01703.02755.02117.01833.01818.02593.02048.01961.01884.02546.02048.01832.01762.02698.02051.01872.01641.02691.02016.01978.01902.02631.02186.02269.01866.02484.02042.01882.01735.02498.02020.01745.01758.02788.02265.01989.01737.02628.02000.0NANANANANA
 Net profit Margin dei:LegalEntity so:MississippiPower▅▅▃▆▄▃▄█▅▄▅▇▄▅▃▇▅▃▃▇▃▂▂▇▃▃▂▇▅▆▃▆▅▂▁▅▃▁▁▆▄▃▂▆▃303.0307.0277.0336.0283.0277.0294.0370.0313.0287.0308.0358.0297.0302.0271.0341.0303.0272.0277.0352.0277.0257.0246.0341.0275.0276.0245.852354.623310.975331.161267.582325.206306.435245.934235.779305.419266.084228.714237.794325.766286.041263.276255.526327.083276.821NANANANANA
 Net profit Margin dei:LegalEntity so:SouthernCompanyGas▂█▄▁▂▅▅▁▂▇▄▁▂█▄▂▂▇▅▁677.01694.01072.0477.0636.01249.01131.0498.0689.01474.01048.0492.0730.01639.01079.0565.0716.01560.01109.0543.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 Net profit Margin dei:LegalEntity so:SouthernPower▅▄▄▆▄▃▄▇▆▅▆█▇▆▅█▆▅▄▆▃▂▂▄▃▃▃▄▂▃▂▃▂▂▂▃▂▁▂▃▂▂▁▃▁490.0440.0396.0523.0439.0375.0411.0574.0510.0443.0506.0635.0555.0509.0478.0618.0529.0450.0389.0500.0373.0315.0304.0401.0337.0348.0386.336435.256328.803350.854300.257364.767307.255302.947291.591354.971285.805253.681286.4362.565305.209281.787268.547356.83248.476NANANANANA
 Net profit Margin us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee so:SNG,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesNANANA150.0149.0NANA152.0155.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 Operating Margin dei:LegalEntity so:AlabamaPower▅▅▃▇▃▃▃█▄▃▂▇▄▄▃▇▄▃▂▇▄▂▁▆▄▃▂▆▃▄▂▅▃▂▂▆▃▁▂▆▄▂▂▆▄1556.01559.01385.01729.01365.01351.01363.01841.01513.01408.01316.01740.01503.01473.01433.01740.01484.01382.01329.01785.01444.01331.01217.01695.01455.01401.01328.01669.01437.01508.01314.01604.01392.01308.01290.01637.01377.01216.01271.01671.01440.01320.01313.01706.01462.0NANANANANA
 Operating Margin dei:LegalEntity so:GeorgiaPower▅▃▃▇▃▂▁█▄▂▂▇▃▃▂▇▃▂▂▇▄▂▁▇▃▃▃▇▄▅▂▆▃▂▂▆▃▂▂█▅▃▂▇▃2225.01970.01938.02617.01928.01825.01703.02755.02117.01833.01818.02593.02048.01961.01884.02546.02048.01832.01762.02698.02051.01872.01641.02691.02016.01978.01902.02631.02186.02269.01866.02484.02042.01882.01735.02498.02020.01745.01758.02788.02265.01989.01737.02628.02000.0NANANANANA
 Operating Margin dei:LegalEntity so:MississippiPower▅▅▃▆▄▃▄█▅▄▅▇▄▅▃▇▅▃▃▇▃▂▂▇▃▃▂▇▅▆▃▆▅▂▁▅▃▁▁▆▄▃▂▆▃303.0307.0277.0336.0283.0277.0294.0370.0313.0287.0308.0358.0297.0302.0271.0341.0303.0272.0277.0352.0277.0257.0246.0341.0275.0276.0245.852354.623310.975331.161267.582325.206306.435245.934235.779305.419266.084228.714237.794325.766286.041263.276255.526327.083276.821NANANANANA
 Operating Margin dei:LegalEntity so:SouthernCompanyGas▂█▄▁▂▅▅▁▂▇▄▁▂█▄▂▂▇▅▁677.01694.01072.0477.0636.01249.01131.0498.0689.01474.01048.0492.0730.01639.01079.0565.0716.01560.01109.0543.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 Operating Margin dei:LegalEntity so:SouthernPower▅▄▄▆▄▃▄▇▆▅▆█▇▆▅█▆▅▄▆▃▂▂▄▃▃▃▄▂▃▂▃▂▂▂▃▂▁▂▃▂▂▁▃▁490.0440.0396.0523.0439.0375.0411.0574.0510.0443.0506.0635.0555.0509.0478.0618.0529.0450.0389.0500.0373.0315.0304.0401.0337.0348.0386.336435.256328.803350.854300.257364.767307.255302.947291.591354.971285.805253.681286.4362.565305.209281.787268.547356.83248.476NANANANANA
 Operating Margin us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName,us-gaap:EquityMethodInvestmentNonconsolidatedInvestee so:SNG,us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvesteesNANANA150.0149.0NANA152.0155.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
 TTM Greenblatt ROC _ _▄▅▄▆▅▅▄▆▅█▄▆▃▅▄▆▁▅▄▆▅▄▄▅▅▄▄▅▅▄▄▅▄▄▄▅▅▄▄▅▅▄▄▅▄▄▄708.01598.0729.01835.01058.01263.0690.02013.01342.03691.0578.02174.063.01376.0794.02045.0-1594.01306.0587.01917.01185.0933.0578.01649.01098.0957.0561.01278.01103.0700.0799.01491.0640.0325.0814.01740.01143.0766.0589.01652.01136.0854.0470.01459.0951.0922.0477.0NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:ComprehensiveIncomeNetOfTax ▅▆▄▆▅▅▅▆▆█▄▆▄▆▅▆▁▅▄▆▅384.01163.0335.01271.0616.0821.0399.01275.0864.02084.0252.01175.0-142.0968.0488.01078.0-1383.0649.0242.01161.0620.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest ▁█388.01135.0NA1303.0625.0794.0NA1304.0896.02059.0NA1233.0-115.0966.0NA1118.0-1350.0649.0NA1152.0609.0371.0276.0944.0651.0493.0NANANA353.0451.0854.0302.085.0372.0976.0616.0374.0231.0897.0608.0426.0155.0819.0515.0504.0NANANANA
us-gaap:CostOfGoodsAndServicesSold ▁█231.0583.0NA71.0144.0439.0NA79.0191.0686.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:CostsAndExpenses ▅▄▅▄▃▄▄▄▄▁▅▄▆▅▅▄█▅▅▄▃▃▃▄▃▃4490.04312.04388.03785.03562.03755.04224.03982.03756.01721.04759.03985.05564.04996.04834.04156.07024.04465.04594.04347.03274.03032.02990.03752.03239.03226.0NANANA3944.03128.03526.03606.03572.02889.03309.03038.02838.03107.03776.03385.03158.03301.03861.03257.03235.0NANANANA
us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal NA41.030.01.0-3.038.0-5086.05.09.02503.0-615.0359.0-34.0-1.0-62.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal dei:LegalEntity so:SouthernPower▁█▁▁▁█▁▁▅▁0.039.00.00.00.039.00.01.023.00.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal dei:LegalEntity,us-gaap:DisposalGroupClassification,us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations,us-gaap:SubsequentEventType so:SouthernCompanyGas,us-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperations,so:Sequent,us-gaap:SubsequentEventNANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal dei:LegalEntity,us-gaap:PublicUtility so:SouthernPower,so:WindGeneratingFacility▁█0.037.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest ▄▅▄▆▄▅▄▆▅█▄▆▃▅▄▆▁▅▄▆▅▄▄▅▅▅364.01297.0307.01576.0626.0986.0335.01712.01076.03419.0120.01845.0-266.01049.0324.01699.0-1935.0980.0239.01616.0908.0719.0415.01470.0945.0799.0NANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeTaxExpenseBenefit ▃▄▃▄▃▄▃▄▄█▃▅▃▄▂▅▁▄▃▅▄▄▄▅▄▄-12.0190.0-50.0293.05.0145.0-74.0367.0145.01360.0-149.0623.0-139.0113.0-175.0590.0-587.0315.09.0448.0272.0222.0118.0500.0302.0274.0NANANA176.0192.0468.0158.031.0236.0569.0329.0200.096.0543.0349.0231.0101.0442.0247.0236.0NANANANA
 us-gaap:IncomeTaxExpenseBenefit dei:LegalEntity so:AlabamaPower▅▅▃▅▄▄▁▆▄▃▂▅▄▄▄█▆▅▄█▆▅▄▇▅▅▄▇▅▅▄▇▅▄▄▇▅▄▄▇▅▄▄▆▅104.0110.030.0130.093.084.0-25.0144.089.062.019.0127.064.082.075.0216.0151.0126.065.0221.0142.0103.079.0192.0122.0113.083.0183.0119.0127.088.0174.0119.097.083.0184.0126.084.071.0180.0131.096.064.0158.0119.0NANANANANA
 us-gaap:IncomeTaxExpenseBenefit dei:LegalEntity so:GeorgiaPower▂▃▂▅▃▃▃▆▅▄▃▇▁▄▅█▆▅▄█▆▅▅█▅▅▄▇▅▅▅▇▅▅▅▇▅▄▄▇▅▄▃▆▅-50.018.0-46.0172.011.016.06.0255.0129.081.02.0262.0-143.093.0125.0350.0199.0156.043.0365.0213.0160.0112.0337.0180.0140.069.0317.0177.0166.0123.0299.0177.0124.0130.0314.0152.092.042.0303.0169.0111.020.0224.0116.0NANANANANA
 us-gaap:IncomeTaxExpenseBenefit dei:LegalEntity so:MississippiPower▆▆▆▆▆▆▆▆▆▆▅▆▆▆█▆▁▆▆▆▆▆▆▆▆▆▆▅▆▅▆▆▅▅▆▆▆▆▆▆▆▆▆▆▆8.04.0-6.012.02.06.03.015.05.07.0-125.014.013.0-4.0353.024.0-881.0-27.0-75.0-2.0-17.0-10.0-61.0-31.016.04.0-32.198-139.3315.92-129.597-12.679-32.687-153.327-169.1428.04721.70512.2148.4253.8718.57812.5877.1588.64418.7599.129NANANANANA
 us-gaap:IncomeTaxExpenseBenefit dei:LegalEntity so:SouthernCompanyGas▁▄▃▂▂▃▃▁▂▃▁█▃▄▄▃▂▅▃▂-29.0121.075.03.016.079.069.0-22.06.077.0-11.0316.055.0104.0134.052.031.0150.069.07.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:IncomeTaxExpenseBenefit dei:LegalEntity so:SouthernPower▇▇▇█▇▇▇█▇▇█▇▇▇▁▇▇▇▇▇▇▇▇▇▇█▇█▇▇▇█▇█████▇█████▇-2.0-10.0-24.014.06.07.0-15.019.0-51.0-9.075.0-38.0-73.0-99.0-810.0-39.0-38.0-52.0-29.0-102.0-41.0-23.07.01.01.012.0-25.40521.96-2.9693.1868.6317.5924.84314.8316.78733.12629.29313.415-1.72732.59324.15720.83428.38430.0677.469NANANANANA
us-gaap:IncomeTaxesPaidNet ▆▄▅▆▅▄▅▅▇▅▅▆▅▅▂▂▅▅▅▄▅▃▅▅█▁139.0-51.0-2.074.08.0-16.011.055.0210.00.035.0133.05.0-1.0-223.0-188.07.0-6.03.0-13.03.0-141.04.03.0273.0-289.0NANANA-7.0-10.07.0138.04.032.040.0-36.02.0-43.0-3.02.0-357.0-2.0-7.0279.06.0NANANANA
us-gaap:InterestAndDebtExpense ▄▄█▃▃▅▃▂▁▁▅▅▇▅450.0450.0478.0443.0444.0456.0442.0434.0429.0430.0456.0458.0470.0458.0NANA424.0416.0404.0374.0293.0246.0228.0218.0180.0213.0NANANA206.0196.0202.0215.0211.0210.0218.0220.0211.0219.0217.0199.0222.0229.0225.0219.0222.0NANANANA
us-gaap:InterestPaidNet ▅█▄█▅▇▄▇▅▇▅▇▆█▆▇▅▇▄▄▂▂▂▂▁▂365.0519.0337.0494.0362.0490.0333.0474.0382.0462.0392.0475.0428.0499.0414.0453.0372.0461.0334.0308.0234.0224.0219.0216.0167.0207.0NANANA186.0195.0180.0197.0187.0214.0198.0213.0178.0463.0-50.0222.0197.0200.0202.0205.0182.0NANANANA
us-gaap:NetIncomeLoss 372.0NANANA612.0NA440.01316.0899.02084.0278.01164.0-154.0938.0496.01069.0-1381.0658.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:NetIncomeLossAttributableToNoncontrollingInterest ▄▁▁▆▄▁▁▆▆▂▃█▆▃▄▆▆▃▄▆▅▄▅▄▄▄-1.0-32.0-34.028.05.0-31.0-36.025.029.0-29.0-13.054.023.0-6.0-2.030.022.0-4.0-3.027.012.01.014.00.00.00.0NANANA17.017.017.016.016.016.017.016.016.016.017.016.016.016.017.016.016.0NANANANA
 us-gaap:NetIncomeLossAttributableToNoncontrollingInterest dei:LegalEntity so:SouthernPower▄▁▁▆▄▁▁▆▆▂▃█▆▃▄▆▆▃▄▆▅▄▄▄▄▄▄▄▄▄▄▄▄▄-1.0-32.0-34.028.05.0-31.0-36.025.029.0-29.0-12.054.023.0-6.0-2.030.022.0-4.0-3.027.012.01.0-1.09.06.00.0-0.9191.6471.2320.8160.00.00.00.0NANANANANANANANANANANANANANANANA
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic ▅▆▅▆▅▆▅▆▆█▄▆▃▆▅▆▁▅▄▆▅▅▄▆▅▅▄▅▅▄▅▆▄▄▅▆▅▅▄▆▅▅▄▅▅▅▄▅▅▄372.01135.0387.01251.0612.0868.0409.01316.0899.02084.0269.01164.0-154.0938.0496.01069.0-1381.0658.0197.01130.0612.0485.0271.0959.0629.0508.0283.0718.0611.0351.0414.0852.0297.081.0383.0976.0623.0368.0261.0916.0604.0422.0153.0817.0510.0495.0249.0790.0478.0126.0
us-gaap:NonoperatingIncomeExpense ▄▅▂▆▂▅▄▅▆▅▁▄▄▄▁▄▄▄▄▅▅▇█▇██-344.0-301.0-422.0-259.0-432.0-277.0-355.0-301.0-266.0-272.0-458.0-329.0-329.0-327.0-470.0-346.0-341.0-326.0-348.0-301.0-277.0-214.0-163.0-179.0-153.0-158.0NANANA-156.0-176.0-154.0-169.0-197.0-179.0-178.0-175.0-182.0-216.0-176.0-167.0-185.0-200.0-183.0-178.0-175.0NANANANA
 us-gaap:NonoperatingIncomeExpense dei:LegalEntity so:AlabamaPower██▆▇▇▅▃▄▅▅▃▅▅▄▂▂▃▂▁▂▂▂▄▄▃▅▅▇▅▅▂▅▅▄▃▂▃▂▁▃▂▂▁▂▂-39.0-40.0-49.0-42.0-46.0-54.0-67.0-59.0-57.0-55.0-68.0-57.0-54.0-61.0-70.0-70.0-68.0-72.0-78.0-75.0-72.0-71.0-60.0-64.0-69.0-54.0-56.0-45.0-55.0-57.0-75.0-58.0-55.0-59.0-66.0-70.0-69.0-71.0-76.0-69.0-73.0-71.0-76.0-70.0-70.0NANANANANA
 us-gaap:NonoperatingIncomeExpense dei:LegalEntity so:GeorgiaPower██▄▆▆▆▄▅▅▆▄▅▅▅▁▂▃▄▃▃▃▄▅▅▃▅▃▅▄▄▅▄▃▃▄▄▄▄▅▅▆▅▅▅▆-34.0-32.0-79.0-52.0-54.0-59.0-78.0-67.0-70.0-56.0-83.0-65.0-67.0-68.0-117.0-100.0-88.0-81.0-95.0-87.0-91.0-77.0-64.0-72.0-92.0-74.0-92.0-74.0-79.0-80.0-69.0-82.0-88.0-87.0-85.0-81.0-83.0-81.0-66.0-68.0-54.0-72.0-63.0-66.0-52.0NANANANANA
 us-gaap:NonoperatingIncomeExpense dei:LegalEntity so:MississippiPower▃▃▂▃▃▃▂▂▂▂▁▂▄▂▁▄▅▅▄▅▅▄▄▅█▅▅▅▅▅▆▅▅▅▄▄▃▄▄▄▃▃▃▃▃-3.0-6.0-17.0-8.0-9.0-8.0-19.0-13.0-12.0-12.0-28.0-19.06.0-18.0-24.013.020.015.03.015.014.011.012.014.054.015.014.89915.04322.82724.24825.08823.52116.39114.11810.01910.6120.6883.94.1553.859-0.753-2.943-2.994-2.248-4.754NANANANANA
 us-gaap:NonoperatingIncomeExpense dei:LegalEntity so:SouthernCompanyGas▁▃▇▇▇█▇▇▇█▆▇▇█▆█▇███-125.0-82.0-17.0-12.0-15.0-6.0-12.0-16.0-22.0-6.0-38.0-12.0-25.0-5.0-36.0-1.0-16.0-2.0-6.0-1.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NonoperatingIncomeExpense dei:LegalEntity so:SouthernPower▃▄▃▅▃▃▂▃█▂▂▄▂▂▁▂▂▁▃▄▅▅▆▆▅▅▅▆▅▅▅▆▅▅▆▆▆▆▂▅▆▆▆▅▅-36.0-31.0-37.0-23.0-37.0-37.0-43.0-37.0-1.0-42.0-44.0-28.0-44.0-44.0-49.0-44.0-46.0-51.0-36.0-33.0-21.0-19.0-15.0-17.0-22.0-22.0-22.076-17.472-21.998-21.885-21.885-13.752-22.259-20.651-18.038-17.732-14.143-13.612-41.515-20.044-18.034-18.77-17.684-19.01-19.866NANANANANA
us-gaap:OperatingIncomeLoss ▄▅▄▆▅▅▄▆▅█▄▆▃▅▄▆▁▅▄▆▅▄▄▅▅▄▄▅▅▄▄▅▄▄▄▅▅▄▄▅▅▄▄▅▄▄▄▅▄▄708.01598.0729.01835.01058.01263.0690.02013.01342.03691.0578.02174.063.01376.0794.02045.0-1594.01306.0587.01917.01185.0933.0578.01649.01098.0957.0561.01278.01103.0700.0799.01491.0640.0325.0814.01740.01143.0766.0589.01652.01136.0854.0470.01459.0951.0922.0477.01415.0886.0490.0
us-gaap:OtherComprehensiveIncomeLossNetOfTax ▆▇▁▆▅▁▂▂▂▅▃▆▆▇▄▅▅▄█▆▅12.028.0-52.020.04.0-47.0-42.0-41.0-35.00.0-26.011.012.030.0-7.09.0-2.0-9.045.022.0-3.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherNonoperatingIncomeExpense █▆▅███▄▆▇▇▁▆▇▆▂▄▄▄▂▅▃▃▃▃▃▄108.058.017.0113.0101.0103.013.061.099.078.0-81.057.078.060.0-57.011.0-3.0-6.0-55.021.0-29.0-21.0-21.0-21.0-12.0-8.0NANANA-7.0-61.0-10.0-4.0-6.0-50.01.013.0-2.0-37.0-1.0-4.02.0-67.0-3.0-5.0-2.0NANANANA
us-gaap:PreferredStockDividendsIncomeStatementImpact ▂▂▂▂▂▂▂▂▁▂▂▂▂▂▂▄▅▅▅▅▆▅▆▅▆█4.04.04.04.04.04.04.04.03.04.04.04.04.04.06.010.011.011.011.011.012.011.012.011.014.017.0NANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ProfitLoss ▅▆▅▆▅▅▅▇▆█▄▆▄▆▅▆▁▅▄▆▅▅▄▆▅▅376.01107.0357.01283.0621.0841.0409.01345.0931.02059.0269.01222.0-127.0936.0499.01109.0-1348.0665.0230.01168.0636.0497.0297.0970.0643.0525.0NANANA368.0431.0869.0313.097.0399.0993.0639.0384.0277.0933.0620.0438.0169.0834.0526.0511.0NANANANA
us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax ▅█▅▆▄▄▄▇▅▅▅▆▅▇▅▇▅▆▄▇▃▂▁▅▃▂▂▅▃▃▂▄▃▂▁▄▂▁▁▅▃▂▂▅▂▂▁▃▂▁5422.06900.05326.05755.04765.05018.04914.06282.05222.05412.05337.06159.05627.06372.05629.06201.05430.05771.05181.06264.04459.03965.03568.05401.04337.04183.04017.05339.04467.04644.03927.05017.04246.03897.03703.05049.04181.03604.03696.05428.04521.04012.03771.05320.04208.04157.03510.04682.03885.03666.0
us-gaap:Revenues ▅▇▅▆▄▅▄▇▅▆▅▇▆█▆█▆▇▅█▃▂▁▆▃▃▂▅▃▄▂▅▃▂▁▅▃▁▁▆▃▂▂▅▃▃▁▄▂▁5198.05910.05117.05620.04620.05018.04914.05995.05098.05412.05337.06159.05627.06372.05629.06201.05430.05771.05181.06264.04459.03965.03568.05401.04337.04183.04017.05339.04467.04644.03927.05017.04246.03897.03703.05049.04181.03604.03696.05428.04521.04012.03771.05320.04208.04157.03510.04682.03885.03666.0
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:Assets ████▇▇▇▇▇▇▇▇▇▇▇▆▆▆▆▆▅▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁125907.0125393.0122935.0123158.0119731.0118852.0118700.0117591.0114867.0114096.0116914.0111717.0112777.0111567.0111005.0110315.0108684.0109760.0109697.0106362.090873.078735.078318.075215.074181.071610.070923.067654.066400.064838.064546.064697.063961.063274.063149.061963.060897.059874.059267.057343.056023.055019.055032.0NANANA52046.0NANANA
us-gaap:Liabilities ████▇▇▇▇▆▆▇▆▇▇▇▆▆▆▆▆▃▁▁92870.092034.090410.090367.087479.086645.086650.085509.083445.083118.087584.083328.085761.085218.085153.083956.083274.082482.082803.080015.067262.056389.056175.0NANANA49583.0NANA44637.044407.044788.044790.044155.043770.042242.041691.041093.040607.038628.037959.037472.037748.0NANANA36086.0NANANA
us-gaap:LiabilitiesAndStockholdersEquity ████▇▇▇▇▆▆▇▆▆▆▆▆▅▆▆▅▃▁▁125907.0125393.0122935.0123158.0119731.0118852.0118700.0117591.0114867.0114096.0116914.0111717.0112777.0111567.0111005.0110315.0108684.0109760.0109697.0106362.090873.078735.078318.0NANANA70923.0NANA64838.064546.064697.063961.063274.063149.061963.060897.059874.059267.057343.056023.055019.055032.0NANANA52046.0NANANA
us-gaap:StockholdersEquity NANA27972.0NANANA27505.0NANANA24723.024877.023636.024676.024167.024082.023372.025094.024758.024547.022015.020797.020592.0NANANA19949.0NANA19070.019008.018778.018040.0NA18297.0NANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity dei:LegalEntity so:AlabamaPowerNANA9810.0NANANA8955.0NANANA7477.07585.07401.07335.06829.06866.06707.06641.06323.06402.06224.06199.05992.06000.05849.05789.05752.05762.05608.05563.05502.05602.05466.0NA5398.0NANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity dei:LegalEntity so:GeorgiaPowerNANA16501.0NANANA15065.0NANANA14323.013851.012702.013420.011931.012007.011713.011650.011356.011265.010935.010889.010719.010755.010453.010406.010421.010027.09722.09635.09591.09599.09328.0NA9273.0NANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity dei:LegalEntity so:MississippiPowerNANA1742.0NANANA1652.0NANANA1609.01443.01398.01351.01358.01914.01873.02926.02943.02628.02601.02373.02359.02303.02248.02197.02084.262021.0272170.3921951.2712176.5511731.1591548.679NA1749.208NANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity dei:LegalEntity so:SouthernCompanyGasNANA9767.0NANANA9506.0NANANA8570.08623.09061.0NA9022.0NANANA9109.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity dei:LegalEntity so:SouthernPowerNANA2369.0NANANA2368.0NANANA2968.04113.04518.05209.05138.04448.04407.04409.04430.03405.02776.02466.02483.02061.01767.01753.01751.8561590.1791559.4561561.9791563.9521573.2991519.586NA1522.357NANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:AssetsCurrent ▄▄▃▅▄▄▄▄▃▃▄▄▅▄▄▄▃▃▄▄█▁▂9551.09469.08617.010574.09069.09430.09817.09917.08352.08709.09583.09384.011619.09524.010072.09202.08837.08427.09722.09658.015149.05461.06526.0NANANA6370.0NANA5140.05599.05785.06001.05932.06162.06696.06373.06041.06272.06495.05502.05240.05883.0NANANA5873.0NANANA
us-gaap:CashAndCashEquivalentsAtCarryingValue ▃▄▂█▄▅▄▇▃▃▃▄▄▅▅▄▃▂▄▆▄▁▃▂▁▂▁1582.01770.01065.03379.01879.02164.01975.02931.01383.01361.01396.01847.01980.02284.02130.01841.01433.01094.01975.02669.01897.0754.01404.01109.0813.01112.0710.0NANA590.0659.0682.0424.0515.0628.01256.0659.01044.01315.01516.0437.0410.0447.01259.0266.0339.0690.0NANANA
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents ▃▃▁█▃▄▄▇▂▂▂▃▄▅▄▃▂▁▄1617.01801.01068.03383.01885.02168.01978.02935.01386.01364.01519.01891.02017.02290.02147.01858.01455.01116.01992.0NANANA1420.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:InventoryNet dei:LegalEntity so:NicorGasNANA259.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAssetsCurrent ▅▆▆▆▅▅▅▅▃▃▄▆▄█▆▅▅▇▆▄▁▂▁184.0232.0222.0210.0190.0179.0188.0208.0138.0132.0162.0232.0172.0286.0211.0209.0206.0249.0230.0168.071.090.071.0NANANA50.0NANA70.039.033.035.060.074.060.066.059.046.0100.051.053.059.0NANANA49.0NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:PropertyPlantAndEquipmentGross ███▇▇▇▇▆▆▆▆▆▆▆▆▆▆▆▅▅▂▁▁112783.0111579.0110516.0108831.0107320.0105931.0105114.0103529.0103428.0102673.0103706.0100672.099626.0104499.0103542.0102014.0101021.099774.098416.094174.078112.076553.075118.0NANANA70013.0NANA66369.066021.064793.064150.063586.063251.061980.061577.060073.059744.058079.057817.057408.056731.0NANANA53588.0NANANA
us-gaap:ConstructionInProgressGross ▆▇▅▅▄▄▃▃▂▃▂▃▁▂▁▃▂▇▆█▇▇▆9264.09525.08697.08861.08351.08360.07880.07804.07568.07598.07254.07655.06947.07460.06904.08026.07440.09465.08977.010069.09451.09406.09082.0NANANA7792.0NANA7425.07151.07144.06593.06193.05989.06363.05745.06225.05591.05809.05301.04872.04775.0NANANA4170.0NANANA
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment ██▇▇▇▆▆▆▆▆▆▆▆▇▇▆▆▆▅▅▁▁▁33240.032887.032397.032099.031477.031180.030765.030469.030693.030834.031038.030739.030255.031920.031457.031164.030667.030330.029852.029590.024778.024566.024253.0NANANA24059.0NANA23329.023059.022821.022533.022219.021964.021906.021616.021327.021154.020891.020657.020384.020174.0NANANA19121.0NANANA
us-gaap:AmortizationOfIntangibleAssets ▁▁▂▂▂▂▃▂▂▃▄▄▅▅▇▆▆█▅▅10.011.012.012.013.012.016.014.015.017.019.021.023.026.030.029.029.035.023.025.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:PropertyPlantAndEquipmentNet ███▇▇▇▆▆▆▆▆▅▅▆▆▆▅▆▅▅▂▁▁89623.089037.087634.086397.085029.083965.083080.081713.081174.081637.080797.078432.077192.080947.079872.079741.078686.079811.078446.075554.063893.062552.061114.0NANANA54868.0NANA51573.051208.050200.049317.048687.048390.047274.046566.045855.045010.043797.043279.042701.042002.0NANANA39230.0NANANA
us-gaap:LongTermInvestments ▇▇▇▇▇▇▇▇▇▇▇▇▇███████▁▁▁10553.010496.010386.010302.010194.010178.010334.010528.010649.010511.010296.010482.010427.011474.011510.011613.011566.011552.011420.011340.03325.02789.02752.0NANANA2492.0NANA2407.02348.02275.02224.02230.02189.02159.02155.02194.02118.02056.02232.02266.02271.0NANANA1963.0NANANA
us-gaap:Goodwill ▇▇▇▇▇▇▇▇▇▇▇▇▇███████▁5280.05280.05280.05280.05280.05280.05280.05280.05282.05284.05315.05315.05315.06226.06268.06267.06271.06251.06251.06223.0264.0NA2.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IntangibleAssetsNetExcludingGoodwill ▁▁▁▁▂▂▂▂▂▃▃▄▄▆▇▇▇███▁466.0477.0487.0499.0511.0523.0536.0550.0550.0585.0613.0674.0702.0848.0873.0902.0929.0935.0970.0942.0490.0NA317.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:FiniteLivedIntangibleAssetsNet ▁▂▂▃▃▄▄▅▅▇█391.0402.0412.0424.0436.0448.0461.0475.0475.0510.0538.0NANA773.0798.0827.0854.0860.0895.0867.0415.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:IntangibleAssetsNetIncludingGoodwill dei:LegalEntity so:SouthernPower▁▁▁▂▂▂▂▃▂▃▄▆▆▆▇▇▇██292.0297.0302.0307.0312.0317.0322.0326.0313.0340.0345.0391.0398.0404.0411.0417.0423.0430.0436.0NANANA319.0NANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredTaxAssetsLiabilitiesNet dei:LegalEntity so:SouthernPowerNANA139.0NANANA436.0NANANA1081.0NANANA726.0NANANA442.0NANANA792.0NANANA472.7NANANA120.2NANANA-550.5NANANA-317.9NANANANANANANANANANANA
us-gaap:OperatingLeaseRightOfUseAsset ▁▄▃▂▁▁▃▄▇█1775.01821.01802.01791.01776.01770.01800.01818.01862.01881.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherAssetsNoncurrent ▅▅▅▇▆▅▄▄▄▅▇▆▇█▇▇▆▆▆▄▂▁▁1307.01264.01288.01524.01384.01267.01071.01156.01141.01292.01463.01436.01497.01653.01577.01513.01387.01357.01395.01133.0833.0771.0737.0NANANA904.0NANA705.0551.0586.0547.0570.0549.0568.0455.0451.0481.0491.0479.0433.0436.0NANANA395.0NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:AccountsPayableCurrent ▅▅▆▄▃▂▅▄▄▅█▆▅▅█▇▄▃▆▃▁▂▄2075.02058.02312.01924.01787.01653.02115.01898.01978.02037.02580.02246.02162.02089.02530.02353.01920.01750.02228.01732.01493.01584.01905.0NANANA1593.0NANA1386.01376.01281.01467.01369.01387.01280.01253.01262.01553.01355.01423.01315.01275.0NANANA1329.0NANANA
us-gaap:AccruedIncomeTaxesCurrent ▁▂▂▂▁▁▁▃▃▅█40.071.0130.075.027.025.00.0179.0171.0340.0656.0NANANA6.0176.0125.0258.0193.0375.013.014.019.0NANANA151.0NANA114.013.087.091.038.07.065.017.051.013.046.013.013.08.0NANANA13.0NANANA
us-gaap:LiabilitiesCurrent ▅▅▆▅▃▃▆▄▄▃█▆█▇▇▆▆▆▆▄▂▁▂11660.011586.012079.011750.09334.09553.012546.010534.010999.09919.014286.012965.014366.013630.013594.012603.012751.012284.012917.010567.08514.07856.09129.0NANANA8967.0NANA4835.05536.05704.07346.06439.07014.06569.06088.06317.06577.05657.05699.06037.06472.0NANANA5584.0NANANA
us-gaap:OperatingLeaseLiabilityCurrent ██▇▄▄▂▂▂▂▁245.0244.0241.0235.0235.0230.0229.0229.0228.0226.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesCurrent ▆█▆▅▅▅▄▅▄▃▅▄▄▆▅▃▄▅▃▅▃▁▁956.01118.0968.0848.0915.0868.0830.0881.0793.0754.0852.0763.0808.0923.0868.0752.0799.0867.0683.0851.0694.0564.0590.0NANANA544.0NANA358.0347.0429.0465.0462.0483.0426.0443.0393.0426.0380.0440.0493.0535.0NANANA292.0NANANA
 us-gaap:TaxesPayableCurrent dei:LegalEntity so:AlabamaPower▂▇▁▄█173.0257.0152.0210.0274.0NA78.0NANANANANA137.0NA54.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:TaxesPayableCurrent dei:LegalEntity so:GeorgiaPower▄▁▇▇█322.0239.0407.0415.0442.0NA407.0NANANANA345.0NANA344.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:TaxesPayableCurrent dei:LegalEntity so:MississippiPower▃▁▇█▅63.039.0114.0120.084.0NA105.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:TaxesPayableCurrent dei:LegalEntity so:SouthernCompanyGas▁█▃▁79.094.083.078.0NANA71.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:TaxesPayableCurrent dei:LegalEntity so:SouthernPowerNANA30.0NANANA26.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:LongTermDebtAndCapitalLeaseObligations ██▇▇▇▇▆▆▆▆▆▆▆▇▇▇▇▆▆▆▄▁▁47828.046727.045073.045581.045138.044235.041798.042098.039682.040457.040736.041425.042483.044446.044462.044042.043885.042786.042629.041550.035368.026091.024688.0NANANA20841.0NANA22288.021344.021053.019943.020223.019274.018955.019459.019051.018647.018733.018554.018133.018154.0NANANA18131.0NANANA
us-gaap:DeferredIncomeTaxLiabilitiesNet ▃▃▃▃▃▃▃▃▂▃▂▁▁▂▂█▇8710.08839.08175.08342.08298.08398.07888.07737.07728.07937.06558.06035.05934.06930.06842.014321.013529.0NA14092.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:PensionAndOtherPostretirementDefinedBenefitPlansLiabilitiesNoncurrent ▂▃▄▁▁▁▁▂▃▃▃▂▂▃▄▃▃▄▄█▅▅▆2004.02091.02213.01753.01789.01778.01814.01999.02058.02084.02147.02017.02009.02206.02256.02139.02156.02234.02299.03022.02485.02546.02582.0NANANA2432.0NANA1446.01461.02548.02504.02526.02540.02449.02409.02432.02442.01608.01563.01575.01580.0NANANA2304.0NANANA
us-gaap:MinorityInterest NANA4262.0NANANA4254.0NANANANA3188.03056.0NA1361.0NANANA1854.0NANANA1390.0NANANA977.0NANA756.0756.0756.0756.0707.0707.0707.0707.0707.0707.0707.0707.0707.0707.0NANANA707.0NANANA
 us-gaap:MinorityInterest dei:LegalEntity so:SouthernPowerNANA4262.0NANANA4254.0NANANA4316.03188.03056.01349.01360.01395.01407.01293.01245.01024.0822.0778.0781.0649.0353.0219.0219.488NANANA0.0NANANANANANANANANANANANANANANANANANANA
us-gaap:OtherLiabilitiesNoncurrent ▃▃▂▃▄▄▃▃▁▁▂▂▂▄▄█▅▆▆▄▅▅▅587.0557.0480.0571.0630.0701.0609.0562.0384.0405.0465.0454.0516.0660.0691.01048.0805.0873.0880.0641.0724.0754.0720.0NANANA594.0NANA568.0584.0550.0508.0633.0668.0641.0588.0578.0514.0483.0456.0508.0517.0NANANA346.0NANANA
us-gaap:OperatingLeaseLiabilityNoncurrent ▃▅▃▁▃▃▃▂▇█1604.01652.01611.01570.01611.01610.01615.01601.01702.01720.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo NANA287.0NANANA268.0284.0295.0291.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity so:AlabamaPowerNANA58.0NANANA52.054.053.053.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity so:GeorgiaPowerNANA202.0NANANA198.0205.0203.0202.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity so:MississippiPowerNANA4.0NANANA1.02.02.02.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity so:SouthernCompanyGasNANA14.0NANANA17.017.017.016.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo dei:LegalEntity so:SouthernPowerNANA25.0NANANA23.022.022.022.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree NANA230.0NANANA260.0269.0279.0274.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity so:AlabamaPowerNANA9.0NANANA53.053.052.052.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity so:GeorgiaPowerNANA200.0NANANA197.0198.0198.0197.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity so:SouthernCompanyGasNANA12.0NANANA14.017.016.016.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree dei:LegalEntity so:SouthernPowerNANA27.0NANANA23.023.023.023.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive dei:LegalEntity so:SouthernPowerNANA27.0NANANA24.024.024.024.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity so:AlabamaPowerNANA74.0NANANA1.02.02.01.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity so:GeorgiaPowerNANA701.0NANANA831.0991.0990.0984.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
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 us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive dei:LegalEntity so:SouthernPowerNANA873.0NANANA812.0847.0849.0848.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
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 us-gaap:StockholdersEquity dei:LegalEntity so:AlabamaPowerNANA9810.0NANANA8955.0NANANA7477.07585.07401.07335.06829.06866.06707.06641.06323.06402.06224.06199.05992.06000.05849.05789.05752.05762.05608.05563.05502.05602.05466.0NA5398.0NANANANANANANANANANANANANANANA
 us-gaap:StockholdersEquity dei:LegalEntity so:GeorgiaPowerNANA16501.0NANANA15065.0NANANA14323.013851.012702.013420.011931.012007.011713.011650.011356.011265.010935.010889.010719.010755.010453.010406.010421.010027.09722.09635.09591.09599.09328.0NA9273.0NANANANANANANANANANANANANANANA
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  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
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 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:GeorgiaPower▂▂▁▂▂▂▁▁▂▁▂▂▂▂█▃▂▃▃▃▃▂▃▃▃▃▂▃▃▃▃▃▄▃▃▄▃▂▃▄▃▃▃▃-817.0-913.0-977.0-867.0-864.0-795.0-1092.0-959.0-854.0-980.0-896.0-820.0-725.0-668.0922.0-509.0-759.0-566.0-589.0-588.0-481.0-689.0-556.0-497.0-486.0-405.0-748.0-541.0-437.0-480.0-639.0-444.0-328.0-479.0-506.0-259.0-527.0-681.0-502.0-368.0-493.0-428.0-578.0-548.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:MississippiPower█▇▆▇▇▇▇▇▇▇▇▇▇██▆▆▅▅▅▇▅▅▅▅▅▄▃▃▃▁▂▂▃▁▃▃▃▃▆▆█▆▇-50.0-67.0-123.0-55.0-74.0-71.0-65.0-70.0-65.0-63.0-62.0-62.0-56.0-52.0-21.0-122.0-171.0-190.0-188.0-213.0-82.0-214.0-220.0-226.0-227.0-233.0-289.608-316.536-372.031-361.432-449.118-379.215-421.986-352.426-470.557-367.099-366.736-344.383-327.473-156.992-145.84-52.378-121.025-74.925NANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:SouthernCompanyGas▄▄▄▄▄▄▄▄▄▄▃█▄▄▄▄▄▄▄▁-360.0-308.0-444.0-403.0-377.0-193.0-397.0-403.0-296.0-290.0-451.01830.0-20.0-361.0-378.0-411.0-376.0-405.0-352.0-1715.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:SouthernPower▆▅▆▆▆█▆▆▇▆▇▆▆▆▆▆▆▃▁▃▃▄▃▄▅▆▅▆▆▆▆▅▆▆▆▆▆▆▆▆▆▆▆▆-97.0-504.0-50.0-66.0-110.0600.0-203.0-218.0333.0-79.097.0-47.0-124.0-153.0-132.0-100.0-156.0-1235.0-1789.0-1023.0-1112.0-873.0-1084.0-884.0-532.0-38.0-526.109-26.074-246.581-14.9-58.102-338.132-232.937-66.814-51.183-89.597-143.965-47.712-64.272-59.779-119.577-84.744-200.43-80.539NANANANANANA
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▄▂▃▂▃▃▃▃▁▃▁▃▃▃▃▃▃▄▄█▃▃▂▃▃-63.01734.0-1653.01362.0-470.0185.0462.01256.0-295.0-3353.0527.0-2576.0-393.0629.0-349.0-305.0580.01025.02082.02590.010371.0682.01509.0-571.0166.0596.0NANANA43.0-69.0-733.049.0429.0-72.0-723.0-210.0588.0-221.0-296.0-184.0-151.0-26.0-149.0198.0-1.0NANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:AlabamaPower▅▆▁▆▃▅▃▆▃█▃▃▄▆▃▄▃▆▃▃▃▅▁▃▃▅▃▅▃▃▃▃▃▃▃▃▂▄▁▃▃▃▃▃165.0341.0-489.0389.0-157.0273.0-227.0375.0-194.0811.0-192.0-196.047.0518.0-176.033.0-171.0477.0-194.0-178.0-192.0279.0-539.0-145.0-194.0145.0-136.0227.0-115.0-140.0-205.0-180.0-134.0-95.0-232.0-134.0-389.0106.0-467.0-148.0-156.0-98.0-181.0-200.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:GeorgiaPower▅▇▄▅▆█▆▆▅█▆▅▁▇▂▄▇▇▇▃▅▆▆▂▄▇▇▃▆▅▅▂▄▆▄▃▆▇▅▃▅▆▅▅13.0444.0-191.0-2.0127.0742.0153.0145.0-45.0665.092.028.0-1121.0601.0-768.0-314.0458.0473.0380.0-577.0-64.0119.0181.0-828.0-314.0431.0414.0-667.0121.0-31.0-22.0-729.0-225.085.0-198.0-560.099.0369.0-104.0-655.0-158.081.0-144.060.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:MississippiPower▆▄▃▂▂▂▃▂▂▃▁▁▁▃▂▃▄▃▆▃▃▄▆▃▅▃▄▁▆▅▆▄▅▆▆▆▃█▆▄▄▂▄▃425.090.0-8.0-36.0-80.0-98.0-14.0-43.0-31.05.0-172.0-146.0-200.0-9.0-104.0-13.0130.012.0396.00.0-1.0199.0398.070.0200.030.0102.502-165.927386.737269.247391.404137.595206.001420.334321.338316.7189.792598.94376.58118.991105.782-99.359142.89269.706NANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:SouthernCompanyGas▃▄▄▄▃▃▄▄▄▃▅▁▃▂▅▄▄▃▄█-75.050.0217.0364.0-216.0-185.0366.0287.047.0-402.0431.0-1261.0-345.0-595.0696.0396.0-7.0-344.0309.02090.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:SouthernPower▂▄▂▂▂▁▃▂▁▃▃▂▃▃▂▂▃▃▇▅█▃▇▄▄▃▄▃▃▃▂▃▃▃▃▂▃▃▂▃▃▃▃▃-282.0478.0-312.0-252.0-176.0-632.0-50.0-286.0-705.0-79.0-73.0-442.0206.0-54.0-177.0-368.0-90.0133.01727.0874.01920.0206.01359.0467.0459.05.0282.584-87.94157.266-34.759-230.952212.509102.30447.913-63.11-215.73860.314-10.491-208.491124.1632.072-29.009142.369-89.624NANANANANANA
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect ▁█-184.0733.0NA1498.0-283.0190.0NA1549.022.0-155.0NA-126.0-273.0143.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity so:AlabamaPower█▁108.089.0NA136.03.04.0NA714.0-136.0446.0NA16.033.0109.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity so:GeorgiaPower▄▄20.020.0NA132.0174.0160.0NA439.01.0-103.0NA369.0-1147.0306.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity so:MississippiPower█▁454.0-15.0NA24.0-66.0-186.0NA69.0-13.0-81.0NA151.0103.0-123.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity so:SouthernCompanyGas▁█-263.0292.0NA37.0-190.0265.0NA2.0-1.0-9.0NA-13.0-25.022.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect dei:LegalEntity so:SouthernPower▁█-155.0161.0NA261.0-174.051.0NA-2.0237.0-48.0NA50.060.0-58.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:DeferredIncomeTaxExpenseBenefit ▂▅▃▄▃▃▆▄▄▅▆▄▁▄▅▆▁▅▃▂▆▄▇▄█▄-241.0140.0-45.022.0-160.0-58.0358.0-21.083.0191.0380.052.0-372.034.0151.0285.0-431.0161.0-105.0-301.0283.0-4.0583.038.0670.0113.0NANANA-37.0233.0404.0-49.0-92.0451.0318.0223.0104.0241.0487.0253.0174.0465.0358.0108.0107.0NANANANA
 us-gaap:DeferredIncomeTaxExpenseBenefit dei:LegalEntity so:AlabamaPower▂▂▁▂▂▁▂▁▄▁▃▂▁▂▄▃▄▂▄▃▄▃█▂▂▁▆▁▂▂▁▄▂▂▂▂▂▂▄▅▄▂▄▅54.033.07.033.028.010.049.010.0138.00.070.056.016.032.0149.068.0133.059.0140.092.0107.068.0303.025.044.016.0202.019.024.025.0-2.0147.028.025.032.047.054.031.0109.0176.0115.059.0109.0177.0NANANANANANA
 us-gaap:DeferredIncomeTaxExpenseBenefit dei:LegalEntity so:GeorgiaPower▁▃▃▅▂▃▅▄▅▆▃▆▁▄▆▇▆▆▅▇▆▅▇▅▄▄█▄▅▆▆█▅▅▆▆▆▅▆█▆▅▆▇-223.0-86.0-106.035.0-129.0-73.034.0-8.026.0127.0-75.071.0-218.0-38.0130.0169.088.071.037.0189.0102.055.0161.018.01.0-7.0231.00.025.096.0122.0228.067.059.0134.0115.090.038.078.0233.0133.056.0117.0140.0NANANANANANA
 us-gaap:DeferredIncomeTaxExpenseBenefit dei:LegalEntity so:MississippiPowerNANA15.0-6.0-9.0-4.027.026.0-8.0-8.055.0131.0134.0155.0432.0-299.0-813.0-47.0-101.050.0-12.0-4.0259.0-176.0553.0141.0-13.135266.10816.602-124.158-5.257-53.976-163.085-174.08238.9967.2472.49-1.2136.53943.361-18.15110.01542.1143.036NANANANANANA
 us-gaap:DeferredIncomeTaxExpenseBenefit dei:LegalEntity so:SouthernCompanyGas▂█▅▂▄▄▇▄▄▄▆▁▁▅▂▇▆▅▇▂-50.0160.057.0-41.018.022.0117.037.017.042.082.0-71.0-59.047.0-29.0121.098.046.0122.0-30.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:DeferredIncomeTaxExpenseBenefit dei:LegalEntity so:SouthernPower▆▆▇▆▇▆▇▆▆▇▇▆▅▆▂█▇▇▃▁▇▅▅██▆▅▆▇▆▇▇▆▇▇▇▇▇▇▆▇▇▇▆-12.0-8.034.0-25.02.0-36.048.0-59.0-80.017.098.0-85.0-202.0-50.0-503.0149.055.036.0-395.0-597.061.0-132.0-180.0163.0113.0-54.0-161.77-3.17810.925-14.08787.9769.6380.10613.58780.78789.07249.0049.9174.007-11.8413.7148.60154.529-6.005NANANANANANA
us-gaap:IncreaseDecreaseInAccountsPayable ▅▄▇▅▅▂█▅▄▁█▆▅▃▆▅▆▂▇▅▅▅▅▅▆▃39.0-216.0401.039.037.0-504.0462.0-110.0-262.0-783.0539.0158.019.0-425.0187.0-114.0180.0-533.0310.062.01.0-72.0-87.045.0115.0-426.0NANANA-109.0212.0-88.0-5.0-47.0151.0-73.0-31.0-136.0150.0-213.0166.0-108.086.0-30.048.0-100.0NANANANA
us-gaap:NetCashProvidedByUsedInOperatingActivities ▄▃▄▆▅▂▂▆▄▁▃▆▄▄▃▇▅▂▁▆▃▂▃█▃▂1662.01242.01476.02373.01953.0894.0900.02368.01769.0744.01361.02326.01749.01509.01142.02511.01845.0897.0632.02147.01250.0865.01186.02981.01194.0913.0NANANA1103.01686.02464.01210.0737.0854.02287.01189.0568.01305.02209.01391.0998.0464.02112.0677.0738.0NANANANA
us-gaap:NetIncomeLoss 372.0NANANA612.0NA440.01316.0899.02084.0278.01164.0-154.0938.0496.01069.0-1381.0658.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:ProfitLoss ▅▆▅▆▅▅▅▇▆█▄▆▄▆▅▆▁▅▄▆▅▅▄▆▅▅376.01107.0357.01283.0621.0841.0409.01345.0931.02059.0269.01222.0-127.0936.0499.01109.0-1348.0665.0230.01168.0636.0497.0297.0970.0643.0525.0NANANA368.0431.0869.0313.097.0399.0993.0639.0384.0277.0933.0620.0438.0169.0834.0526.0511.0NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ▆▅▆▅▆▆▅▆▆█▅▇▆▆▆▆▆▅▅▅▁▅▅▆▆▆-1783.0-2243.0-2138.0-2237.0-1766.0-889.0-2319.0-2075.0-1452.02454.0-2260.0124.0-1629.0-1995.0-504.0-1798.0-2086.0-2803.0-3408.0-3965.0-10478.0-2197.0-2400.0-2114.0-1659.0-1107.0NANANA-1215.0-1640.0-1473.0-1350.0-1279.0-1410.0-967.0-1364.0-1427.0-1285.0-834.0-1180.0-884.0-1250.0-970.0-948.0-1088.0NANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:AlabamaPower▅▅▄▁▆▅▄▅▅▄▂▄▄▄▃▅▅▆▆▆▆▆▅▅▆▆▄▆▆▇▆▇▇▇▇█▇▇▇█▆▇▇█-427.0-466.0-531.0-808.0-359.0-424.0-524.0-437.0-491.0-511.0-689.0-525.0-511.0-564.0-659.0-458.0-430.0-329.0-356.0-341.0-373.0-368.0-439.0-423.0-313.0-313.0-564.0-394.0-354.0-255.0-381.0-233.0-281.0-247.0-288.0-182.0-229.0-235.0-255.0-177.0-333.0-224.0-251.0-189.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:GeorgiaPower▂▂▁▂▂▂▁▁▂▁▂▂▂▂█▃▂▃▃▃▃▂▃▃▃▃▂▃▃▃▃▃▄▃▃▄▃▂▃▄▃▃▃▃-817.0-913.0-977.0-867.0-864.0-795.0-1092.0-959.0-854.0-980.0-896.0-820.0-725.0-668.0922.0-509.0-759.0-566.0-589.0-588.0-481.0-689.0-556.0-497.0-486.0-405.0-748.0-541.0-437.0-480.0-639.0-444.0-328.0-479.0-506.0-259.0-527.0-681.0-502.0-368.0-493.0-428.0-578.0-548.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:MississippiPower█▇▆▇▇▇▇▇▇▇▇▇▇██▆▆▅▅▅▇▅▅▅▅▅▄▃▃▃▁▂▂▃▁▃▃▃▃▆▆█▆▇-50.0-67.0-123.0-55.0-74.0-71.0-65.0-70.0-65.0-63.0-62.0-62.0-56.0-52.0-21.0-122.0-171.0-190.0-188.0-213.0-82.0-214.0-220.0-226.0-227.0-233.0-289.608-316.536-372.031-361.432-449.118-379.215-421.986-352.426-470.557-367.099-366.736-344.383-327.473-156.992-145.84-52.378-121.025-74.925NANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:SouthernCompanyGas▄▄▄▄▄▄▄▄▄▄▃█▄▄▄▄▄▄▄▁-360.0-308.0-444.0-403.0-377.0-193.0-397.0-403.0-296.0-290.0-451.01830.0-20.0-361.0-378.0-411.0-376.0-405.0-352.0-1715.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NetCashProvidedByUsedInInvestingActivities dei:LegalEntity so:SouthernPower▆▅▆▆▆█▆▆▇▆▇▆▆▆▆▆▆▃▁▃▃▄▃▄▅▆▅▆▆▆▆▅▆▆▆▆▆▆▆▆▆▆▆▆-97.0-504.0-50.0-66.0-110.0600.0-203.0-218.0333.0-79.097.0-47.0-124.0-153.0-132.0-100.0-156.0-1235.0-1789.0-1023.0-1112.0-873.0-1084.0-884.0-532.0-38.0-526.109-26.074-246.581-14.9-58.102-338.132-232.937-66.814-51.183-89.597-143.965-47.712-64.272-59.779-119.577-84.744-200.43-80.539NANANANANANA
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▅▅▇█▄▄█▆▅▅█▆▇▅█▆▆▃▇▅▄▆█▂▁▁1706.01678.02076.02163.01642.01560.02138.01933.01806.01678.02208.01965.02047.01781.02181.01844.01910.01488.02058.01766.01614.01872.02184.01251.01148.01091.0NANANA1180.01485.01381.01400.01197.01251.01202.01125.01231.01410.0989.01040.01086.01192.0958.0882.01054.0NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▄▂▃▂▃▃▃▃▁▃▁▃▃▃▃▃▃▄▄█▃▃▂▃▃-63.01734.0-1653.01362.0-470.0185.0462.01256.0-295.0-3353.0527.0-2576.0-393.0629.0-349.0-305.0580.01025.02082.02590.010371.0682.01509.0-571.0166.0596.0NANANA43.0-69.0-733.049.0429.0-72.0-723.0-210.0588.0-221.0-296.0-184.0-151.0-26.0-149.0198.0-1.0NANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:AlabamaPower▅▆▁▆▃▅▃▆▃█▃▃▄▆▃▄▃▆▃▃▃▅▁▃▃▅▃▅▃▃▃▃▃▃▃▃▂▄▁▃▃▃▃▃165.0341.0-489.0389.0-157.0273.0-227.0375.0-194.0811.0-192.0-196.047.0518.0-176.033.0-171.0477.0-194.0-178.0-192.0279.0-539.0-145.0-194.0145.0-136.0227.0-115.0-140.0-205.0-180.0-134.0-95.0-232.0-134.0-389.0106.0-467.0-148.0-156.0-98.0-181.0-200.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:GeorgiaPower▅▇▄▅▆█▆▆▅█▆▅▁▇▂▄▇▇▇▃▅▆▆▂▄▇▇▃▆▅▅▂▄▆▄▃▆▇▅▃▅▆▅▅13.0444.0-191.0-2.0127.0742.0153.0145.0-45.0665.092.028.0-1121.0601.0-768.0-314.0458.0473.0380.0-577.0-64.0119.0181.0-828.0-314.0431.0414.0-667.0121.0-31.0-22.0-729.0-225.085.0-198.0-560.099.0369.0-104.0-655.0-158.081.0-144.060.0NANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:MississippiPower▆▄▃▂▂▂▃▂▂▃▁▁▁▃▂▃▄▃▆▃▃▄▆▃▅▃▄▁▆▅▆▄▅▆▆▆▃█▆▄▄▂▄▃425.090.0-8.0-36.0-80.0-98.0-14.0-43.0-31.05.0-172.0-146.0-200.0-9.0-104.0-13.0130.012.0396.00.0-1.0199.0398.070.0200.030.0102.502-165.927386.737269.247391.404137.595206.001420.334321.338316.7189.792598.94376.58118.991105.782-99.359142.89269.706NANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:SouthernCompanyGas▃▄▄▄▃▃▄▄▄▃▅▁▃▂▅▄▄▃▄█-75.050.0217.0364.0-216.0-185.0366.0287.047.0-402.0431.0-1261.0-345.0-595.0696.0396.0-7.0-344.0309.02090.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:NetCashProvidedByUsedInFinancingActivities dei:LegalEntity so:SouthernPower▂▄▂▂▂▁▃▂▁▃▃▂▃▃▂▂▃▃▇▅█▃▇▄▄▃▄▃▃▃▂▃▃▃▃▂▃▃▂▃▃▃▃▃-282.0478.0-312.0-252.0-176.0-632.0-50.0-286.0-705.0-79.0-73.0-442.0206.0-54.0-177.0-368.0-90.0133.01727.0874.01920.0206.01359.0467.0459.05.0282.584-87.94157.266-34.759-230.952212.509102.30447.913-63.11-215.73860.314-10.491-208.491124.1632.072-29.009142.369-89.624NANANANANANA
us-gaap:ProceedsFromIssuanceOfLongTermDebt █▁2496.02150.0NA3250.01640.02653.0NA3347.0170.01220.0NA850.0500.0600.0NA1110.01549.01409.0NA2053.010041.01997.0NA917.02525.0550.0NANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:RepaymentsOfLongTermDebt █▁2093.0384.0NA28.0963.01481.0NA656.0131.02429.0NA1119.02096.01283.0NA503.0870.0608.0NA1133.0384.0888.0NA1623.0606.0333.0NANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:PaymentsOfDividendsCommonStock █▇▇▇▇▇▆▆▆▆▅▅▅▄▄▄▄▃▃▃▃▂▂▁▂▁699.0678.0677.0676.0677.0655.0651.0650.0646.0623.0620.0611.0608.0586.0584.0582.0578.0556.0551.0530.0526.0497.0494.0493.0494.0478.0NANANA451.0448.0444.0444.0426.0426.0430.0427.0410.0408.0406.0402.0385.0382.0379.0376.0359.0NANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value5268525751645140506650545038501849974973495249004708460445724539446744614447441744004389438643774346432843124291424842194101
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.34.44.44.64.54.54.54.54.64.54.54.65.25.85.86.46.96.96.96.97.07.07.17.27.37.37.57.77.77.77.9

us-gaap:CommonStockValue dei:LegalEntity

so:MississippiPower


Common
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value38383838383838383838383838383838383837373737373737373737373737373737
Percentage of CommonStockValue0.70.70.70.70.80.80.80.80.80.80.80.80.80.80.80.00.00.00.80.00.00.80.80.80.90.90.90.90.90.90.90.90.90.9
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.1
Percentage of Assets so:MississippiPower0.80.80.80.80.80.80.80.80.70.50.50.50.50.50.50.50.50.50.60.60.60.60.60.70.70.70.70.70.80.91.01.31.51.5

so:SouthernCompanyGas


Common
Period End2020-12-312019-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value993096970.00.00.00.00.00.00.00.0
Percentage of CommonStockValue188.5184.50.00.00.00.00.00.00.00.0
Percentage of Assets8.18.20.00.00.00.00.00.00.00.0
Percentage of Assets so:SouthernCompanyGas43.944.70.00.00.00.00.00.00.00.0

Shares Issued

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

us-gaap:SharesIssued

so:AlabamaPower, us-gaap:CommonStock


Shares
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-31
Value313131313131313131313131313131313131313131313125
Percentage of SharesIssued100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:MississippiPower, us-gaap:CommonStock


Shares
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312014-12-312013-12-312012-12-312011-12-312010-12-312009-12-312008-12-31
Value1.01.01.01.01.01.01.01.01.01.01.01.01.01.01.01.01.01.1211.1211.1211.1211.1211.1211.121
Percentage of SharesIssued3.23.23.23.23.23.23.23.23.23.23.23.23.23.23.23.23.23.63.63.63.63.63.64.5

us-gaap:SharesIssued us-gaap:StatementEquityComponents

us-gaap:CommonStock


Shares
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value10601060105810571057105710541050104610411034102910151012100810041000995991980942921915912911911908900896894892889883880877877875869865862858849843839831825820777763
Percentage of SharesIssued3419.43419.43412.93409.73409.73409.73400.03387.13374.23359.03337.93322.23274.63266.43253.30.00.00.03197.50.00.00.02951.80.00.00.02930.70.00.00.02879.80.00.00.02831.60.00.00.02792.50.00.00.02722.00.00.00.02645.73110.50.0

us-gaap:TreasuryStock


Shares
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value1.01.01.01.01.01.01.01.01.00.9920.9531.01.00.9620.9290.8193.3523.3323.2993.3350.7250.7020.9353.2615.6478.1091010103.1440.5650.545-0.539-0.519-0.499-0.475-0.474-0.475-0.442-0.488-0.505-0.424-0.399
Percentage of SharesIssued3.23.23.23.23.23.23.23.23.23.23.13.23.23.13.02.610.80.00.00.02.30.00.00.018.20.00.00.032.40.00.00.0-1.70.00.00.0-1.50.00.00.0-1.6-1.70.0

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding dei:LegalEntity

us-gaap:CommonStockSharesOutstanding

so:MississippiPower


Common
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value1.01.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.1211.121
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Diluted Shares Outstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding

us-gaap:WeightedAverageNumberOfDilutedSharesOutstanding


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value10671066106410631067105710521045102910141016101010051000975940922912912915893881879875883880877868862853842833824
Percentage of WeightedAverageNumberOfDilutedSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Weighted Average Number Of Shares Outstanding Basic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic

us-gaap:WeightedAverageNumberOfSharesOutstandingBasic


Weighted
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-302015-06-302015-03-312014-03-312013-09-302013-06-302013-03-312012-09-302012-06-302012-03-312011-09-302011-06-302011-03-312010-09-302010-06-302010-03-31
Value106110601058105810571048104410381023101410111003998993968934916910909910890878874870876872868860855847836828822
Percentage of WeightedAverageNumberOfSharesOutstandingBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value0.351.070.371.180.580.820.421.260.862.010.271.14-0.150.930.491.07-1.380.660.21.170.650.530.31.050.690.560.310.80.680.390.470.970.340.090.441.110.710.420.31.070.710.50.180.980.620.60.310.990.610.16
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.351.060.361.180.580.810.421.250.851.990.271.13-0.150.920.491.06-1.370.660.21.160.650.530.31.050.690.560.310.80.680.390.470.970.340.090.441.110.710.420.291.060.70.490.170.970.610.6
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value38411633351271616821399127586420842521175-142.09684881078-1383.06492421161620
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax7.116.90.022.112.916.48.120.316.538.54.719.1-2.515.28.717.4-25.511.24.718.513.9

us-gaap:ComprehensiveIncomeNetOfTax dei:LegalEntity

so:SouthernPower


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value33113128260421.07816652-62.0922614579512977584219878
Percentage of ComprehensiveIncomeNetOfTax8.69.73.66.59.75.10.36.119.22.5-24.67.8-18.315.0162.912.0-5.68.917.417.112.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.61.60.01.41.30.80.01.23.21.0-1.21.50.52.314.12.11.41.00.83.21.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower10.438.20.024.722.411.20.221.052.711.7-12.314.54.728.5166.320.914.612.910.839.620.9

Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value38811351303625794130489620591233-115.09661118-1350.0649115260937127694465149335345185430285372976616374231897608426155819515504
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax7.216.422.613.115.820.817.238.020.0-2.015.218.0-24.911.218.413.79.47.717.515.011.87.611.517.07.12.210.019.314.710.46.216.513.410.64.115.412.212.1

us-gaap:ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest dei:LegalEntity

so:AlabamaPower


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3363644493032854743002223782632303312361793552171581272932121751242921831971492681841511522781741309825618915453259189
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest86.632.134.548.535.936.333.510.830.7-228.723.829.6-17.527.630.835.642.646.031.032.635.50.00.00.055.833.031.460.9177.640.928.528.234.842.428.531.136.234.231.636.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.25.37.86.45.77.55.74.16.14.73.65.34.33.15.74.94.03.65.44.94.23.15.54.14.23.85.34.33.94.15.54.23.62.74.74.23.81.44.94.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower23.624.726.923.121.125.420.115.821.717.515.619.015.913.019.915.011.910.417.314.612.59.317.512.713.111.316.713.211.511.817.012.610.77.715.313.111.70.015.212.9

so:GeorgiaPower


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value144353775310330804421312665-395.035358535326560335327320154529722612352931727021249228720219852629516811052130920756422241
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest37.131.159.549.641.661.747.015.253.9343.536.552.3-26.140.852.358.073.672.857.745.645.80.00.00.076.547.057.695.0237.653.253.947.944.947.658.150.848.636.151.546.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.75.113.56.56.612.88.15.810.8-7.05.59.46.54.69.67.96.95.610.16.85.43.19.97.15.85.49.86.85.25.310.47.14.73.09.66.85.21.57.95.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower6.918.530.616.018.128.820.317.025.6-19.318.023.017.214.522.317.214.612.220.314.711.46.520.114.511.911.419.814.110.711.421.114.69.66.318.713.610.40.016.112.0

so:MississippiPower


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value38456739326537374747-8.039-2053.0-19.0263.011-69.0-21.05035-23.412-194.42563-171.40413-23.47-218.464-245.6763554352416282514163315
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest9.84.05.16.24.05.04.11.83.8-40.9-0.83.5152.1-2.92.30.53.0-25.0-2.27.77.10.00.00.0-48.63.0-2.7-72.3-289.09.45.65.76.67.13.24.23.410.44.13.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.71.20.80.61.00.70.70.80.8-0.10.6-37.8-0.30.40.10.3-1.9-0.41.20.8-0.6-3.61.4-3.70.3-0.5-5.1-6.30.91.10.80.70.40.50.60.40.40.60.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower13.115.420.014.111.617.211.912.913.115.8-2.611.4-677.6-7.07.41.14.3-28.0-6.218.212.7-9.5-54.820.3-51.85.1-7.2-71.3-99.914.918.013.210.86.98.98.85.60.010.35.5

so:SouthernCompanyGas


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-30
Value-57.04021971260-32.010326952-30.028115482371.0
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest-14.735.41.511.432.7-2.511.513.14.226.129.11.3-3.636.50.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.15.80.31.55.2-0.52.05.00.8-0.54.40.20.94.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-4.213.52.07.220.8-3.59.618.210.6-4.117.12.76.715.20.2

so:SouthernPower


Comprehensive
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3381110651110319523146491391599958198785135102463344633033238529303270483025574640226531
Percentage of ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest8.57.18.410.41.47.921.81.111.8-42.614.414.2-7.38.917.212.813.712.710.87.16.70.00.00.09.55.210.09.836.38.77.27.88.211.16.47.69.414.78.06.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.61.21.91.40.21.63.70.42.40.92.22.61.81.03.21.71.31.01.91.10.81.11.20.70.70.61.70.70.80.91.41.20.80.71.11.01.00.61.20.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower10.427.433.124.32.927.761.95.223.08.827.325.718.712.939.620.916.211.525.413.69.511.514.69.49.67.823.49.610.211.119.816.912.09.015.915.114.20.018.512.5

Cost Of Goods And Services Sold

us-gaap:CostOfGoodsAndServicesSold

us-gaap:CostOfGoodsAndServicesSold


Cost
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value2315837114443979191686
Percentage of CostOfGoodsAndServicesSold100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.38.41.23.08.71.33.712.7

us-gaap:CostOfGoodsAndServicesSold dei:LegalEntity, us-gaap:ProductOrService

so:AlabamaPower, so:ElectricityPurchasedAffiliates


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value393035443018367369216769433755
Percentage of CostOfGoodsAndServicesSold16.95.10.062.020.84.10.092.436.13.10.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.40.00.80.60.40.71.21.30.41.31.10.80.60.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower so:ElectricityPurchasedAffiliates0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:AlabamaPower, srt:Fuel


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value263291249306199215248310252301273356
Percentage of CostOfGoodsAndServicesSold113.949.90.0431.0138.249.00.0392.4131.943.90.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.94.20.05.34.24.35.04.94.85.65.15.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower srt:Fuel0.00.00.00.00.00.00.00.00.00.00.00.0

so:AlabamaPower, us-gaap:ElectricityPurchased


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value485038644940437747374064486457
Percentage of CostOfGoodsAndServicesSold20.88.60.090.134.09.10.097.524.65.40.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.90.70.01.11.00.80.91.20.90.70.71.00.91.00.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower us-gaap:ElectricityPurchased0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:GeorgiaPower, so:ElectricityPurchasedAffiliates


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value149136116142122129115150134176168206178171161
Percentage of CostOfGoodsAndServicesSold64.523.30.0200.084.729.40.0189.970.225.70.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.72.00.02.52.62.62.32.42.63.33.13.33.22.72.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower so:ElectricityPurchasedAffiliates0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:GeorgiaPower, srt:Fuel


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value343313315368226231312443390299429480
Percentage of CostOfGoodsAndServicesSold148.553.70.0518.3156.952.60.0560.8204.243.60.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.34.50.06.44.74.66.37.17.55.58.07.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower srt:Fuel0.00.00.00.00.00.00.00.00.00.00.00.0

so:GeorgiaPower, us-gaap:ElectricityPurchased


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value14414413114613312912815112411892106111121119
Percentage of CostOfGoodsAndServicesSold62.324.70.0205.692.429.40.0191.164.917.20.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.72.10.02.52.82.62.62.42.42.21.71.72.01.91.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower us-gaap:ElectricityPurchased0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:MississippiPower, srt:Fuel


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value91101841038379881211059393116
Percentage of CostOfGoodsAndServicesSold39.417.30.0145.157.618.00.0153.255.013.60.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.71.50.01.81.71.61.81.92.01.71.71.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower srt:Fuel0.00.00.00.00.00.00.00.00.00.00.00.0

so:MississippiPower, us-gaap:ElectricityPurchased


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value115.04.06.07.05.05.06.06.03.014117.09.06.0
Percentage of CostOfGoodsAndServicesSold4.80.90.08.54.91.10.07.63.10.40.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.20.10.00.10.10.10.10.10.10.10.30.20.10.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower us-gaap:ElectricityPurchased0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:NaturalGasUsRegulated


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2315833187114443936379191686486104228720516134
Percentage of CostOfGoodsAndServicesSold100.0100.00.0100.0100.0100.00.0100.0100.0100.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.38.40.01.23.08.77.41.33.712.79.11.74.111.39.22.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:NaturalGasUsRegulated0.00.00.00.00.00.00.00.00.00.00.021.40.00.00.025.2

so:SouthernPower, srt:Fuel


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value140141124137102107128166139145188190
Percentage of CostOfGoodsAndServicesSold60.624.20.0193.070.824.40.0210.172.821.10.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.62.00.02.42.12.12.62.62.72.73.53.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower srt:Fuel0.00.00.00.00.00.00.00.00.00.00.00.0

so:SouthernPower, us-gaap:ElectricityPurchased


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-30
Value252022191814262632243937396143
Percentage of CostOfGoodsAndServicesSold10.83.40.026.812.53.20.032.916.83.50.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.50.30.00.30.40.30.50.40.60.40.70.60.71.00.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower us-gaap:ElectricityPurchased0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

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

so:SouthernCompanyGas, so:WholesaleGasServices


Cost
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value142923531134891116312121238
Percentage of CostOfGoodsAndServicesSold618.6403.61597.2618.8264.91534.2648.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax26.434.119.718.723.219.323.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas so:WholesaleGasServices0.00.00.00.00.00.00.0

us-gaap:CostOfGoodsAndServicesSold us-gaap:ProductOrService

srt:Fuel


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value848848777933621636786107291485011231310
Percentage of CostOfGoodsAndServicesSold367.1145.50.01314.1431.2144.90.01357.0478.5123.90.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax15.612.30.016.213.012.716.017.117.515.721.021.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax srt:Fuel0.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ElectricityPurchased


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value217207188230200181191254201170211257236267217256
Percentage of CostOfGoodsAndServicesSold93.935.50.0323.9138.941.20.0321.5105.224.80.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.03.00.04.04.23.63.94.03.83.14.04.24.24.23.94.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ElectricityPurchased0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NaturalGasUsRegulated


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2315833187114443936379191686486104228720516134
Percentage of CostOfGoodsAndServicesSold100.0100.00.0100.0100.0100.00.0100.0100.0100.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.38.40.01.23.08.77.41.33.712.79.11.74.111.39.22.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:NaturalGasUsRegulated0.00.00.00.00.00.00.00.00.00.00.021.10.00.00.025.2

us-gaap:ProductAndServiceOther


Cost
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value103821267274551191148411811812027928922090
Percentage of CostOfGoodsAndServicesSold44.614.10.0101.451.412.50.0144.344.017.20.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.91.20.01.31.61.12.41.81.62.22.21.95.04.53.91.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ProductAndServiceOther0.00.00.00.00.00.00.00.00.00.00.060.30.00.00.053.6

Costs And Expenses

us-gaap:CostsAndExpenses

us-gaap:CostsAndExpenses


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value4490431243883785356237554224398237561721475939855564499648344156702444654594434732743032299037523239322639443128352636063572288933093038283831073776338531583301386132573235
Percentage of CostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax82.862.50.065.874.874.886.063.471.931.889.264.798.978.485.967.0129.477.488.769.473.476.583.869.574.777.184.979.770.384.991.778.065.572.778.784.169.674.978.787.572.677.477.8

us-gaap:CostsAndExpenses dei:LegalEntity

so:AlabamaPower


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value10781046117411099249291229116510681070115211791123110111651124103010061076113510149989531140105710551061114910801127100211041035100110191093987925101311481036991110912091073
Percentage of CostsAndExpenses24.024.326.829.325.924.729.129.328.462.224.229.620.222.024.127.014.722.523.426.131.032.931.930.432.632.70.00.00.028.632.031.328.728.035.333.032.532.632.630.430.631.433.631.332.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax19.915.20.019.319.418.525.018.520.519.821.619.120.017.320.718.119.017.420.818.122.725.226.721.124.425.226.421.524.224.325.522.024.425.727.521.623.625.727.421.122.924.729.422.725.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower75.970.90.066.470.468.890.262.471.776.087.567.874.774.781.364.669.472.881.063.670.275.078.367.372.675.379.968.875.274.776.368.874.476.579.066.871.776.179.768.771.975.10.070.973.4

so:GeorgiaPower


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value209815691741162015551419149615941470138515621602252014481415151214091331150416441395136312651727146215241614171116141753146216121490147013351574148514011536189317281596159619141589
Percentage of CostsAndExpenses46.736.439.742.843.737.835.440.039.180.532.840.245.329.029.336.420.129.832.737.842.645.042.346.045.147.20.00.00.044.446.745.741.341.246.247.648.949.449.450.151.050.548.349.648.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax38.722.70.028.132.628.330.425.428.225.629.326.044.822.725.124.425.923.129.026.231.334.435.532.033.736.440.232.036.137.737.232.135.137.736.131.235.538.941.634.938.239.842.336.037.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower100.782.10.064.180.477.887.857.171.075.685.961.8123.073.875.159.468.872.785.460.968.072.877.164.272.577.084.965.073.877.378.364.973.078.176.963.073.580.387.467.976.380.20.072.879.5

so:MississippiPower


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value2542522522492332312722772592312572782432954502903257334444343305267387407263252316703254656291405694675204239219198221272246238227272247
Percentage of CostsAndExpenses5.75.85.76.66.56.26.47.06.913.45.47.04.45.99.37.046.47.59.77.99.38.812.910.88.17.80.00.00.016.69.311.519.318.97.17.27.27.07.17.27.37.56.97.07.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.73.70.04.34.94.65.54.45.04.34.84.54.34.68.04.760.05.88.65.56.86.710.87.56.16.07.913.25.714.17.48.116.417.35.54.75.25.56.05.05.55.96.05.15.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower87.686.30.074.384.483.492.573.583.580.583.477.781.897.7166.185.01074.9122.8160.397.4110.1103.9157.3119.495.691.3128.8198.482.0198.3109.1124.6226.7274.586.678.382.386.893.183.786.390.40.083.289.3

so:SouthernCompanyGas


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value6461093750448534889812533555112194311868112519694976201169924531
Percentage of CostsAndExpenses14.425.317.111.815.023.719.213.414.865.119.83.012.225.020.012.08.826.220.112.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax11.915.80.07.811.217.716.58.510.620.717.71.912.119.617.28.011.420.317.88.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas47.936.70.047.253.971.271.858.452.076.190.024.093.376.389.888.086.674.983.397.8

so:SouthernPower


Costs
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value420354391384328287396407357383476499539449446459417385360366292268249272262281346330277291246248252238225235195197222253218204200245189
Percentage of CostsAndExpenses9.48.28.910.19.27.69.410.29.522.310.012.59.79.09.211.05.98.67.88.48.98.88.37.28.18.70.00.00.07.47.97.07.06.77.87.16.47.07.26.76.56.56.16.45.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax7.75.10.06.76.95.78.16.56.87.18.98.19.67.07.97.47.76.76.95.86.56.87.05.06.06.78.66.26.26.36.34.95.96.16.14.74.75.56.04.74.85.15.34.64.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower132.9119.60.0115.7122.476.596.4109.4113.386.594.178.697.188.293.374.378.885.692.573.278.385.181.967.877.780.789.675.984.583.182.168.182.178.777.466.468.577.877.870.071.672.60.068.776.3

Disposal Group Not Discontinued Operation Gain Loss On Disposal

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal


Disposal
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-31
Value41301.0-3.038-5086.05.09.02503-615.0359-34.0-1.0-62.0
Percentage of DisposalGroupNotDiscontinuedOperationGainLossOnDisposal100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.60.00.0-0.10.8-103.50.10.246.2-11.55.8-0.6-0.0-1.1

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal dei:LegalEntity

so:SouthernPower


Disposal
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0390.00.00.0390.01.0230.0
Percentage of DisposalGroupNotDiscontinuedOperationGainLossOnDisposal0.095.10.00.0-0.0102.6-0.020.0255.60.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.60.00.00.00.80.00.00.40.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower0.013.20.00.00.010.40.00.37.30.0

us-gaap:DisposalGroupNotDiscontinuedOperationGainLossOnDisposal dei:LegalEntity, us-gaap:DisposalGroupClassification, us-gaap:IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperations, us-gaap:SubsequentEventType

so:SouthernCompanyGas, us-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperations, so:Sequent, us-gaap:SubsequentEvent


Disposal
Period End2021-07-01
Value90
Percentage of DisposalGroupNotDiscontinuedOperationGainLossOnDisposal0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:DisposalGroupDisposedOfBySaleNotDiscontinuedOperations so:Sequent us-gaap:SubsequentEvent0.0

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

so:SouthernPower, so:WindGeneratingFacility


Disposal
Period End2021-06-302021-03-31
Value0.037
Percentage of DisposalGroupNotDiscontinuedOperationGainLossOnDisposal0.090.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower so:WindGeneratingFacility0.00.0

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

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value364129730715766269863351712107634191201845-266.010493241699-1935.098023916169087194151470945799
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.718.80.027.413.119.66.827.320.663.22.230.0-4.716.55.827.4-35.617.04.625.820.418.111.627.221.819.1

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest dei:LegalEntity

so:AlabamaPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value4394731625783953686761738828396504326311198546386304174575358262204491329292211475302324237442302248205474321220182454331258128427319
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest120.636.552.836.763.137.320.036.036.18.380.027.3-122.629.661.132.1-19.931.072.835.639.436.449.233.434.836.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax8.16.90.010.08.37.31.49.87.45.21.88.25.84.93.58.87.15.33.49.28.06.65.79.17.67.05.38.96.87.06.08.87.16.45.59.47.76.14.98.47.36.43.48.07.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower30.932.10.034.630.127.24.933.126.020.17.329.021.721.113.831.426.022.013.132.224.819.716.829.022.620.815.928.521.021.518.027.621.719.015.929.023.318.114.327.223.019.50.025.021.8

so:GeorgiaPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value933691189453193471281094577392174926-539.044535293455142016396756543231289246238019684649343633579046432531584345226315682748332178648359
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest25.528.538.460.051.035.238.263.953.611.5145.050.2202.642.4108.655.0-28.542.968.259.862.260.175.260.748.947.60.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.75.30.016.46.76.92.617.411.07.23.315.0-9.67.06.315.110.17.33.115.412.710.98.716.510.79.14.915.811.09.48.515.710.98.38.516.710.87.34.215.210.78.02.112.28.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower4.519.30.037.416.519.07.539.227.921.49.635.7-26.322.718.736.726.922.99.335.827.523.119.033.122.919.210.332.222.619.218.031.822.717.318.233.722.415.18.929.721.316.10.024.717.9

so:MississippiPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value46498.07941383.0804244246160-11.0-202.064-2934.0-47.0-163.024-14.01.0-130.0-52.06639-55.822-333.96778-301.2120.676-56.369-372.004-415.034176473420573822255224
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest12.63.82.65.06.53.90.94.73.91.320.03.3-22.6-1.0-62.33.8151.6-4.8-68.21.5-1.50.1-31.3-3.57.04.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.80.70.01.40.90.80.11.30.80.80.41.01.1-0.2-3.61.0-54.0-0.8-3.10.4-0.30.0-3.6-1.01.50.9-1.4-6.31.8-6.50.0-1.1-8.8-10.61.11.51.10.90.61.10.80.60.71.00.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower15.916.80.023.614.913.71.021.213.515.37.817.020.2-3.6-74.518.8-968.3-17.3-58.86.8-5.10.4-52.8-15.224.014.1-22.7-94.225.4-91.00.3-17.3-121.4-168.817.725.117.914.98.617.513.48.40.016.19.0

so:SouthernCompanyGas


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-94.05193051787354307-51.0112347673622438374678038917911
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest-25.840.099.31.113.935.991.6-3.010.410.155.819.6-9.036.522.83.9-4.139.774.90.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.77.50.00.31.87.16.2-0.82.16.41.35.90.46.01.31.11.56.73.50.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-7.017.40.01.88.828.327.1-5.610.523.56.473.63.323.46.911.911.224.916.12.0

so:SouthernPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3455-32.01167451-28.013015218-14.0108-28.016-17.01156614-8.010160284011253451887293731102324447101754222886858509239
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest9.34.2-10.47.411.85.2-8.47.614.10.5-11.75.910.51.5-5.26.8-3.41.4-3.36.26.63.99.67.65.65.60.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.60.80.02.01.61.0-0.62.12.90.3-0.31.8-0.50.3-0.31.91.20.2-0.21.61.30.71.12.11.21.10.41.60.70.80.82.00.81.11.32.01.81.20.61.61.51.51.31.70.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower10.818.60.034.927.613.6-6.834.948.34.1-2.817.0-5.03.1-3.618.612.53.1-2.120.216.18.913.227.915.712.94.720.08.810.710.628.210.714.516.428.626.616.87.724.522.520.80.026.015.7

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxExpenseBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-12.0190-50.02935.0145-74.03671451360-149.0623-139.0113-175.0590-587.03159.04482722221185003022741761924681583123656932920096543349231101442247236
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.22.80.05.10.12.9-1.55.82.825.1-2.810.1-2.51.8-3.19.5-10.85.50.27.26.15.63.39.37.06.63.84.99.33.70.86.411.37.95.52.610.07.75.82.78.35.95.7

us-gaap:IncomeTaxExpenseBenefit dei:LegalEntity

so:AlabamaPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value104110301309384-25.014489621912764827521615112665221142103791921221138318311912788174119978318412684711801319664158119
Percentage of IncomeTaxExpenseBenefit-866.757.9-60.044.41860.057.933.839.261.44.6-12.820.4-46.072.6-42.936.6-25.740.0722.249.352.246.466.938.440.441.20.00.00.072.245.837.275.3312.935.232.338.342.074.033.137.541.663.435.748.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.91.60.02.32.01.7-0.52.31.71.10.42.11.11.31.33.52.82.21.33.53.22.62.23.62.82.72.13.42.72.72.23.52.82.52.23.63.02.31.93.32.92.41.73.02.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower7.37.50.07.87.16.2-1.87.76.04.41.47.34.35.65.212.410.29.14.912.49.87.76.511.38.48.16.211.08.38.46.710.88.57.46.411.29.26.95.610.89.17.30.09.38.1

so:GeorgiaPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-50.018-46.017211166.0255129812.0262-143.0931253501991564336521316011233718014069317177166123299177124130314152924230316911120224116
Percentage of IncomeTaxExpenseBenefit416.79.592.058.7220.011.0-8.169.589.06.0-1.342.1102.982.3-71.459.3-33.949.5477.881.578.372.194.967.459.651.10.00.00.094.364.163.9112.0400.055.155.246.246.043.855.848.448.119.850.747.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.90.30.03.00.20.30.14.12.51.50.04.3-2.51.52.25.63.72.70.85.84.84.03.16.24.23.31.75.94.03.63.16.04.23.23.56.23.62.61.15.63.72.80.54.22.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower-2.40.90.06.80.60.90.49.16.24.40.110.1-7.04.76.613.79.78.52.413.510.48.56.812.58.97.13.612.08.17.36.612.08.76.67.512.67.55.32.410.97.55.60.08.55.8

so:MississippiPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value8.04.0-6.0122.06.03.0155.07.0-125.01413-4.035324-881.0-27.0-75.0-2.0-17.0-10.0-61.0-31.0164.0-32.198-139.3315-129.597-12.679-32.687-153.327-169.1428.04721128.4253.8718127.1588.644189.129
Percentage of IncomeTaxExpenseBenefit-66.72.112.04.140.04.1-4.14.13.40.583.92.2-9.4-3.5-201.74.1150.1-8.6-833.3-0.4-6.2-4.5-51.7-6.25.31.50.00.00.0-73.6-6.6-7.0-97.0-545.63.43.83.74.24.03.43.63.18.64.23.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.10.00.20.00.10.10.20.10.1-2.30.20.2-0.16.30.4-16.2-0.5-1.4-0.0-0.4-0.3-1.7-0.60.40.1-0.8-2.60.4-2.8-0.3-0.7-3.6-4.30.20.40.30.20.10.30.30.20.20.40.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower2.81.40.03.60.72.21.04.01.62.4-40.63.94.4-1.3130.37.0-290.8-9.9-27.1-0.6-6.1-3.9-24.8-9.15.81.4-13.1-39.35.1-39.1-4.7-10.1-50.0-68.83.47.14.63.71.65.74.42.70.05.73.3

so:SouthernCompanyGas


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-29.0121753.0167969-22.06.077-11.0316551041345231150697.0
Percentage of IncomeTaxExpenseBenefit241.763.7-150.01.0320.054.5-93.2-6.04.15.77.450.7-39.692.0-76.68.8-5.347.6766.71.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.51.80.00.10.31.61.4-0.40.11.4-0.25.11.01.62.40.80.62.61.30.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-2.14.10.00.31.66.36.1-2.40.65.2-1.064.27.56.312.49.24.39.66.21.3

so:SouthernPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-04-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-2.0-10.0-24.0146.07.0-15.019-51.0-9.075-38.0-73.0-4.0-99.0-810.0-39.0-38.0-52.0-29.0-102.0-41.0-23.07.01.01.012-25.40521-2.9693.1868.63174.8431416332913-1.72732242028307.469
Percentage of IncomeTaxExpenseBenefit16.7-5.348.04.8120.04.820.35.2-35.2-0.7-50.3-6.152.50.0-87.6462.9-6.66.5-16.5-322.2-22.8-15.1-10.45.90.20.34.40.00.00.01.84.53.83.147.87.15.88.96.7-1.86.06.99.028.16.83.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.0-0.10.00.20.10.1-0.30.3-1.0-0.21.4-0.6-1.30.0-1.6-14.4-0.6-0.7-0.9-0.6-1.6-0.9-0.60.20.00.00.3-0.60.4-0.10.10.20.40.10.40.50.70.70.4-0.00.60.50.50.80.60.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower-0.6-3.40.04.22.21.9-3.65.1-16.2-2.014.8-6.0-13.20.0-19.4-169.5-6.3-7.2-11.6-7.5-20.4-11.0-7.32.30.20.33.4-6.65.0-0.90.92.94.81.64.95.89.310.25.3-0.69.07.97.40.08.43.0

Income Taxes Paid Net

us-gaap:IncomeTaxesPaidNet

us-gaap:IncomeTaxesPaidNet


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value139-51.0-2.0748.0-16.011552100.0351335.0-1.0-223.0-188.07.0-6.03.0-13.03.0-141.04.03.0273-289.0-7.0-10.07.01384.03240-36.02.0-43.0-3.02.0-357.0-2.0-7.02796.0
Percentage of IncomeTaxesPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.6-0.70.01.30.2-0.30.20.94.00.00.72.20.1-0.0-4.0-3.00.1-0.10.1-0.20.1-3.60.10.16.3-6.9-0.2-0.30.13.30.10.90.8-0.90.1-1.2-0.10.0-8.9-0.1-0.16.60.1

us-gaap:IncomeTaxesPaidNet dei:LegalEntity

so:AlabamaPower


Income
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-16.0203-63.026630.076138.09.09058880.0-38.05240-162.0740.0183-136.020986169-28.01428.0149-3.01371419.022-44.05.010.0-110.0-24.08.0
Percentage of IncomeTaxesPaidNet800.0274.3-572.747.330.00.0217.19.8160.0-900.0-40.4-30.91257.1-0.0-1266.7-400.01333.3114.91850.00.067.047.10.00.00.0400.0-1420.0114.3108.0-75.0428.1352.5-25.01100.0102.3-166.7500.030.81200.0-114.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.03.5-1.30.41.20.01.40.20.10.11.60.91.60.0-0.70.80.9-4.12.10.04.2-3.35.21.63.8-0.63.60.23.5-0.13.72.80.20.6-1.20.10.2-2.7-0.60.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower0.012.1-4.61.44.20.05.80.70.50.66.33.35.90.0-2.92.92.8-12.26.10.012.6-9.715.75.211.8-1.910.80.510.7-0.210.68.60.71.8-3.50.30.7-8.30.00.5

so:GeorgiaPower


Income
Period End2020-12-312020-09-302019-12-312019-09-302018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value62311655115977640.0127156218-5.0-18.0110166-88.019571274-34.0198164134111899.0973.01261421628561362-77.04211
Percentage of IncomeTaxesPaidNet-3100.0420.3590.992.7454.357.91280.0-0.0-57.0-83.03114.383.3-600.0-846.25533.362.44875.02366.7100.411.80.00.00.0-157.1-1890.0128.670.375.0393.8355.0-44.41400.0-130.2-433.33100.021.6-2100.0-157.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.05.41.30.83.01.31.10.02.32.54.0-0.1-0.31.83.7-2.25.51.36.3-0.84.93.13.00.24.80.22.30.13.42.80.40.81.50.21.4-1.91.10.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower0.012.33.81.88.73.03.10.06.76.110.6-0.3-1.04.18.1-4.711.92.613.6-1.710.46.26.10.510.10.44.80.27.35.70.81.63.20.52.7-3.90.00.4

so:MississippiPower


Income
Period End2020-12-312020-09-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value199.0-27.0-23.0230.0-42.0-226.0-276.019-215.0-116.0-93.00.0134-109.0-98.0-24.022126-1.0-180.0-168.693-176.844-59.69926-85.89115-64.037-0.025-65.843-3.9814.238-11.994-7.748-0.628-0.354-32.294-3.7992.112
Percentage of IncomeTaxesPaidNet-950.012.2-245.5-41.811.00.0-120.0-169.9-5520.0-1900.096.461.7-1328.6-0.04466.7838.5-3266.717.0550.04200.0-0.462.30.00.00.0-372.5858.9225.1-46.4-0.6-205.8-10.0-11.8-599.718.020.9-17.79.0189.9-30.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.2-0.5-0.40.40.0-0.8-3.7-4.90.3-3.8-1.9-1.70.02.6-1.7-2.2-0.60.62.3-0.0-4.3-4.2-3.3-1.30.6-2.20.3-1.5-0.0-1.8-0.10.1-0.3-0.2-0.0-0.0-0.8-0.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower0.02.7-9.2-6.17.40.0-13.6-63.1-92.96.3-79.3-34.0-30.70.048.4-31.0-35.4-9.38.937.0-0.4-65.2-68.6-49.9-19.27.9-32.14.8-20.9-0.0-27.9-1.31.6-5.2-3.3-0.2-0.1-12.30.00.6

so:SouthernCompanyGas


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value101-1.0-20.0498.0-12.0-89.0-48.097-1.0-158.05761060.055-3.0200.0-31.054
Percentage of IncomeTaxesPaidNet72.72.01000.066.2100.075.0-809.1-87.346.20.0-451.4433.12120.0-0.0-24.71.6285.7-0.0-1033.3-415.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.9-0.00.00.90.2-0.2-1.8-0.81.9-0.0-3.09.41.90.01.0-0.00.40.0-0.60.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas7.5-0.00.05.20.8-1.0-7.9-5.39.1-0.1-15.1117.114.50.05.1-0.52.80.0-2.89.9

so:SouthernPower


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-187.0-2.0-5.0-273.00.0-5.0-52.0-191.0-422.01.0181-211.0148-39.0-144.0-226.0-116.0-1.045-44.0-73.0188-303.0-143.0-151.079-128.448-32.045-14.68-44.468-219.661-2.719-3.62-0.179-37.513-151.4642.888100.0694.58713-44.7211.9122.378
Percentage of IncomeTaxesPaidNet-134.53.9250.0-368.90.031.2-472.7-347.3-201.00.0517.1-158.62960.03900.064.6120.2-1657.116.71500.0338.5-2433.3-133.3-7575.0-4766.7-55.3-27.30.00.00.0635.32196.6-38.8-2.6-4.5-117.2-378.7-8.0541.0-0.2-152.9679.012.5-95.6-34.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-3.4-0.00.0-4.70.0-0.1-1.1-3.0-8.10.03.4-3.42.6-0.6-2.6-3.6-2.1-0.00.9-0.7-1.64.7-8.5-2.6-3.51.9-3.2-0.6-0.3-1.0-5.6-0.1-0.1-0.0-1.0-3.00.10.30.00.10.3-1.10.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower-59.2-0.70.0-82.20.0-1.3-12.7-51.3-134.00.235.8-33.226.7-7.7-30.1-36.6-21.9-0.211.6-8.8-19.659.7-99.7-35.7-44.822.7-33.2-7.4-4.5-12.7-73.2-0.7-1.2-0.1-12.9-42.71.04.30.01.34.4-15.90.00.7

Interest And Debt Expense

us-gaap:InterestAndDebtExpense

us-gaap:InterestAndDebtExpense


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value450450478443444456442434429430456458470458424416404374293246228218180213206196202215211210218220211219217199222229225219222
Percentage of InterestAndDebtExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax8.36.50.07.79.39.19.06.98.27.98.57.48.47.27.87.27.86.06.66.26.44.04.25.14.45.04.05.15.45.74.35.35.95.94.04.45.56.14.25.25.3

us-gaap:InterestAndDebtExpense dei:LegalEntity

so:AlabamaPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value84848384838888838283838280797775787774736971696567636362636565667071737375737774767676
Percentage of InterestAndDebtExpense18.718.717.419.018.719.319.919.119.119.318.217.917.017.218.218.019.320.625.329.730.332.638.330.50.00.00.030.132.132.230.231.333.332.633.234.634.233.638.733.333.233.834.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.51.20.01.51.71.81.81.31.61.51.61.31.41.21.41.31.51.21.71.81.91.31.61.61.71.21.41.31.61.31.51.71.91.41.72.02.01.31.71.82.01.41.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower5.95.70.05.06.36.56.54.45.55.96.34.75.35.45.25.45.94.35.15.55.74.24.74.65.03.84.44.14.84.14.75.05.44.35.36.05.94.45.35.60.04.55.2

so:GeorgiaPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value1061041031061051111051031059694951021061041019898999491909389868890848292969190959091869071961009587
Percentage of InterestAndDebtExpense23.623.121.523.923.624.323.823.724.522.320.620.721.723.124.524.324.326.233.838.239.941.351.741.80.00.00.040.841.845.544.743.142.943.640.943.139.341.535.743.243.742.239.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.01.50.01.82.22.22.11.62.01.81.81.51.81.71.91.81.91.62.22.42.61.72.12.12.11.62.01.82.11.82.32.32.41.92.22.52.31.71.62.42.71.82.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower5.15.40.04.25.46.16.23.75.15.25.23.75.05.45.15.55.63.64.85.05.53.34.64.54.53.34.13.74.43.74.74.85.23.84.55.24.93.23.14.80.03.64.3

so:MississippiPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value14141514151617171717171921191719281515161313-30.011119.41612126.9558.7281010109.735137.8056.293.8565.5326.0135.334.8865.946
Percentage of InterestAndDebtExpense3.13.13.13.23.43.53.83.94.04.03.74.14.54.14.04.66.94.05.16.55.76.0-16.75.20.00.00.05.83.54.34.84.94.94.55.93.72.91.82.82.72.32.22.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.20.00.20.30.30.30.30.30.30.30.30.40.30.30.30.50.20.30.40.40.2-0.70.30.30.20.30.30.20.20.20.30.30.20.30.20.20.10.10.10.10.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower4.84.80.04.25.45.85.84.55.55.95.55.37.16.35.67.010.14.35.46.25.33.8-10.94.04.62.74.13.62.62.73.44.24.43.24.93.42.61.21.92.30.01.52.1

so:SouthernCompanyGas


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-31
Value59606057575858565959585259594846
Percentage of InterestAndDebtExpense13.113.312.612.912.812.713.112.913.813.712.711.412.612.911.311.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.10.90.01.01.21.21.20.91.11.11.10.81.00.90.90.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas4.42.00.06.05.84.65.16.15.54.05.510.68.13.66.72.9

so:SouthernPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value37383736383942434144454546474850393522211518232222222122201220201717131320191718171819
Percentage of InterestAndDebtExpense8.28.47.78.18.68.69.59.99.610.29.99.89.810.311.312.09.79.47.58.56.68.312.810.30.00.00.010.710.56.49.69.78.47.96.36.59.59.28.98.57.78.48.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.60.00.60.80.80.90.70.80.80.80.70.80.70.90.90.80.60.50.50.40.30.50.50.50.40.50.50.50.30.50.50.50.30.30.40.60.40.40.50.50.40.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower11.712.80.010.814.210.410.211.613.09.98.97.18.39.29.111.110.07.05.96.74.94.56.86.35.75.36.76.36.83.66.76.76.14.84.95.47.35.55.86.70.05.37.9

Interest Paid Net

us-gaap:InterestPaidNet

us-gaap:InterestPaidNet


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value365519337494362490333474382462392475428499414453372461334308234224219216167207186195180197187214198213178463-50.0222197200202205182
Percentage of InterestPaidNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.77.50.08.67.69.86.87.57.38.57.37.77.67.87.47.36.98.06.44.95.25.66.14.03.94.94.05.03.64.64.85.83.95.14.912.5-0.94.94.95.33.84.94.4

us-gaap:InterestPaidNet dei:LegalEntity

so:AlabamaPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value6193728869926592658964775984687756846284557658745068576053616163556470677066796669727489
Percentage of InterestPaidNet16.717.921.417.819.118.819.519.417.019.316.316.213.816.816.417.015.118.218.627.323.533.926.534.329.932.90.00.00.032.831.335.027.934.232.733.832.937.117.1-132.031.136.537.044.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.11.30.01.51.41.81.31.51.21.61.21.31.01.31.21.21.01.51.21.31.21.91.61.41.21.61.41.11.21.31.61.31.31.61.91.31.71.82.11.21.51.82.01.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower4.36.30.05.35.36.84.84.94.46.34.94.43.95.74.74.43.86.14.74.73.85.74.84.43.44.94.33.63.74.04.63.94.04.95.44.15.15.46.23.94.85.50.05.2

so:GeorgiaPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value54128641365812277117879293104961151029898889810388861028191798478867197789772100819858106631126510859
Percentage of InterestPaidNet14.824.719.027.516.024.923.124.722.819.923.721.922.423.024.621.626.319.129.333.437.638.446.637.554.538.20.00.00.038.249.743.349.238.546.740.946.032.622.9-126.050.533.054.029.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.01.90.02.41.22.41.61.91.71.71.71.71.71.81.81.61.81.51.91.62.02.22.91.52.11.92.11.51.91.52.51.62.31.82.71.62.31.62.91.22.51.62.91.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower2.66.70.05.43.06.74.54.24.25.05.14.04.75.95.43.84.84.85.63.84.34.66.23.04.54.04.43.03.93.15.23.14.83.85.83.24.93.36.02.34.93.30.02.2

so:MississippiPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value1516141615181619231323181821201913131410.01412394.03.0-1.02.062-3.4195.3213.0284.7172.1458.5634.869.6416.345160.00.8584.4513.376.1352.7925.704
Percentage of InterestPaidNet4.13.14.23.24.13.74.84.06.02.85.93.84.24.24.84.23.52.84.23.26.05.417.81.91.8-0.50.00.00.01.62.41.24.32.64.53.27.80.00.2-8.91.53.11.42.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.20.00.30.30.40.30.30.40.20.40.30.30.30.40.30.20.20.30.20.30.31.10.10.1-0.00.1-0.10.10.10.10.00.20.10.30.10.40.00.00.10.10.20.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower5.25.50.04.85.46.55.45.07.44.57.55.06.17.07.45.64.34.85.12.85.14.715.91.21.1-0.40.8-1.01.70.91.80.72.82.04.12.16.20.00.41.41.22.30.01.7

so:SouthernCompanyGas


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value7552704370497155705574467752774164414986
Percentage of InterestPaidNet20.510.020.88.719.310.021.311.618.311.918.99.718.010.418.69.117.28.914.727.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.40.80.00.71.51.01.40.91.31.01.40.71.40.81.40.71.20.70.91.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas5.61.70.04.57.13.96.36.06.63.77.19.310.53.27.17.38.92.64.415.8

so:SouthernPower


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value652624276828342778283529802945318528407.027155.034-1.0366.672356.955355.206206.804284.085240.495209.788271026-0.33130
Percentage of InterestPaidNet17.85.07.15.518.85.710.25.720.46.18.96.118.75.810.96.822.86.112.02.311.56.72.315.7-0.617.40.00.00.019.22.711.33.515.01.912.50.211.82.1-55.64.713.7-0.215.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.20.40.00.51.40.60.70.41.50.50.70.51.40.50.80.51.60.50.80.10.60.40.10.6-0.00.90.20.70.20.80.10.40.20.70.10.50.00.60.30.50.20.7-0.00.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower20.68.80.08.125.47.58.37.324.86.36.94.614.45.79.45.016.16.210.31.47.24.81.68.5-0.310.31.78.22.110.21.75.62.29.31.47.00.28.33.47.73.49.60.08.5

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value372612440131689920842781164-154.09384961069-1381.0658
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.912.89.020.917.238.55.218.9-2.714.78.817.2-25.411.4

us-gaap:NetIncomeLoss dei:LegalEntity

so:AlabamaPower


Net
Period End2021-06-302021-03-312020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value3313592982808846929621773373259225119325230174
Percentage of NetIncomeLoss89.00.048.70.020.035.632.910.426.332.0-168.224.024.030.4-16.726.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.15.26.35.61.87.55.74.01.46.14.63.52.15.24.23.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower23.324.322.720.76.525.119.915.45.521.417.215.38.318.715.512.6

so:SouthernCompanyGas


Net
Period End2021-06-302020-06-302019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-65.071238-29.01062707846-31.0279-60.01549239
Percentage of NetIncomeLoss-17.511.654.1-2.211.813.028.14.020.129.7-12.11.4-3.536.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.21.54.8-0.52.05.01.50.7-0.64.4-1.10.20.94.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-4.87.221.0-3.29.918.37.49.3-4.217.0-5.62.76.815.3

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

so:SouthernCompanyGas, us-gaap:OperatingSegments


Net
Period End2021-06-302020-06-30
Value-62.077
Percentage of NetIncomeLoss-16.712.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.11.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments0.00.0

us-gaap:NetIncomeLoss dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasDistributionOperations


Net
Period End2021-06-302020-06-30
Value8074
Percentage of NetIncomeLoss21.512.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.51.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasDistributionOperations0.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasMarketingServices


Net
Period End2021-06-302020-06-30
Value6.05.0
Percentage of NetIncomeLoss1.60.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasMarketingServices0.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasPipelineInvestments


Net
Period End2021-06-302020-06-30
Value-36.021
Percentage of NetIncomeLoss-9.73.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.70.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasPipelineInvestments0.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:WholesaleGasServices


Net
Period End2021-06-302020-06-30
Value-112.0-23.0
Percentage of NetIncomeLoss-30.1-3.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.1-0.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:WholesaleGasServices0.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Net
Period End2021-06-302020-06-30
Value-3.0-6.0
Percentage of NetIncomeLoss-0.8-1.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.1-0.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments us-gaap:CorporateAndOther0.00.0

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

so:AlabamaPower, us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-06-302020-03-31
Value331359298280
Percentage of NetIncomeLoss89.00.048.70.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.15.26.35.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower us-gaap:RetainedEarnings0.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Net
Period End2021-06-302020-06-30
Value-2.010.0
Percentage of NetIncomeLoss-0.51.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.00.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination0.00.0

us-gaap:NetIncomeLoss us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:ElectricUtilities, so:SouthernPower


Net
Period End2021-06-302020-06-30
Value3663
Percentage of NetIncomeLoss9.710.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.71.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:ElectricUtilities so:SouthernPower0.00.0

us-gaap:OperatingSegments, so:ElectricUtilities, so:TraditionalElectricOperatingCompanies


Net
Period End2021-06-302020-06-30
Value511645
Percentage of NetIncomeLoss137.4105.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax9.413.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:ElectricUtilities so:TraditionalElectricOperatingCompanies0.00.0

us-gaap:NetIncomeLoss us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:SouthernCompanyGas


Net
Period End2021-06-302020-06-30
Value-65.071
Percentage of NetIncomeLoss-17.511.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.21.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:SouthernCompanyGas0.00.0

us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Net
Period End2021-06-302020-06-30
Value-108.0-177.0
Percentage of NetIncomeLoss-29.0-28.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.0-3.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments us-gaap:CorporateAndOther0.00.0

us-gaap:NetIncomeLoss us-gaap:ProductOrService

so:ElectricUtilities


Net
Period End2021-06-302020-06-30
Value547708
Percentage of NetIncomeLoss147.0115.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax10.114.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:ElectricUtilities0.00.0

Net Income Loss Attributable To Noncontrolling Interest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-1.0-32.0-34.0285.0-31.0-36.02529-29.0-13.05423-6.0-2.03022-4.0-3.027121.0140.00.00.01717171616161716161617161616171616
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.0-0.50.00.50.1-0.6-0.70.40.6-0.5-0.20.90.4-0.1-0.00.50.4-0.1-0.10.40.30.00.40.00.00.00.40.40.30.40.40.40.30.40.40.40.30.40.40.40.30.40.4

us-gaap:NetIncomeLossAttributableToNoncontrollingInterest dei:LegalEntity

so:SouthernPower


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value-1.0-32.0-34.0285.0-31.0-36.02529-29.0-12.05423-6.0-2.03022-4.0-3.027121.0-1.09.06.00.0-0.9191.6471.2320.8160.00.00.00.0
Percentage of NetIncomeLossAttributableToNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.092.3100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0-7.10.00.00.00.00.00.04.80.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.0-0.50.00.50.1-0.6-0.70.40.6-0.5-0.20.90.4-0.1-0.00.50.4-0.1-0.10.40.30.0-0.00.20.10.0-0.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower-0.3-10.80.08.41.9-8.3-8.86.79.2-6.5-2.48.54.1-1.2-0.44.94.2-0.9-0.85.43.20.3-0.32.21.80.0-0.20.40.40.20.00.00.00.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value37211353871251612868409131689920842691164-154.09384961069-1381.0658197113061248527195962950828371861135141485229781383976623368261916604422153817510495249790478126
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.916.40.021.712.817.38.320.917.238.55.018.9-2.714.78.817.2-25.411.43.818.013.712.27.617.814.512.17.013.413.77.610.517.07.02.110.319.314.910.27.116.913.410.54.115.412.111.97.116.912.33.4

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic dei:LegalEntity

so:AlabamaPower


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value331359128444298280884692962177337325922511932523017410235021115512129520016911928217318714025817314111328018512610226419015255259190
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic89.031.633.135.548.732.321.535.632.910.427.132.0-168.224.024.030.4-16.726.451.831.034.532.044.630.831.833.342.039.328.353.333.830.358.2174.129.528.729.734.239.128.831.536.035.931.737.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.15.20.07.76.35.61.87.55.74.01.46.14.63.52.15.24.23.02.05.64.73.93.45.54.64.03.05.33.94.03.65.14.13.63.15.54.43.52.84.94.23.81.54.94.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower23.324.30.026.622.720.76.525.119.915.45.521.417.215.38.318.715.512.67.719.614.611.69.917.413.712.19.016.912.012.410.716.112.410.88.817.113.410.48.015.813.211.50.015.213.0

so:SouthernCompanyGas


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value3982301471275238-29.01062707846-31.0279-60.015492391104.0
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic35.159.41.111.631.758.2-2.211.813.029.04.020.129.7-12.11.4-3.536.355.80.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.80.00.21.55.54.8-0.52.05.01.50.7-0.64.4-1.10.20.94.12.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas13.40.01.57.222.021.0-3.29.918.37.49.3-4.217.0-5.62.76.815.39.90.7

so:SouthernPower


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value369726746375-12.08617456-60.09222121795124827023176895034102463344633033238527293068462923564437
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic9.78.56.75.910.38.6-2.96.519.42.7-22.37.9-14.312.9160.311.6-5.910.611.715.614.510.312.510.67.36.515.78.95.09.55.610.09.436.08.17.07.58.09.16.17.48.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.71.40.01.31.31.5-0.21.43.31.0-1.11.50.41.914.12.01.51.20.42.82.01.31.01.91.10.81.11.20.70.70.61.70.70.70.81.41.10.80.61.01.00.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower11.432.80.022.323.520.0-2.923.155.212.6-11.914.54.023.8166.320.115.515.65.935.223.915.911.225.413.69.511.514.69.49.57.723.39.19.610.619.316.311.68.315.514.613.4

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic dei:LegalEntity, us-gaap:ConsolidationItems

so:SouthernCompanyGas, us-gaap:OperatingSegments


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value3942202177274271301032739764-15.0289584450231
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic34.756.81.712.631.666.32.311.513.136.15.59.730.811.74.1-3.635.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.70.00.41.65.55.50.52.05.01.81.0-0.34.51.00.70.94.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments0.00.00.00.00.00.00.00.00.00.012.90.00.00.07.20.00.0

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasDistributionOperations


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value183106467416410937581334474681491305254117
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic16.127.43.712.118.926.72.86.56.416.46.4-44.215.926.24.9-3.917.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.70.00.81.63.32.20.61.12.50.81.21.22.32.30.81.02.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasDistributionOperations0.00.00.00.00.00.00.00.00.00.016.80.00.00.011.00.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasMarketingServices


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value5630-3.05.05729-4.0-3.06131-8.0-76.013481.04.031
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic4.97.8-0.20.86.67.1-0.3-0.32.911.5-0.749.41.49.70.1-0.34.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.80.0-0.10.11.10.6-0.1-0.11.10.6-0.1-1.40.20.90.00.10.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasMarketingServices0.00.00.00.00.00.00.00.00.00.0-18.20.00.00.00.70.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasPipelineInvestments


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2925232130316.0253235202127
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic2.66.51.83.43.57.60.52.81.513.01.7-13.62.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.40.00.40.40.60.60.10.50.60.70.30.40.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasPipelineInvestments0.00.00.00.00.00.00.00.00.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:WholesaleGasServices


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value12659-45.0-23.023102-9.02347-27.0-18.0-21.0104-85.0-23.0-17.068
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic11.115.2-3.6-3.82.624.9-0.72.62.3-10.0-1.513.611.1-17.1-2.21.210.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.80.0-0.8-0.50.52.1-0.10.40.9-0.5-0.3-0.41.6-1.5-0.4-0.31.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:WholesaleGasServices0.00.00.00.00.00.00.00.00.00.0225.00.00.00.095.80.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value4.010.0-7.0-6.01.0-33.0-59.03.0
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic0.42.6-0.6-1.00.1-8.1-4.50.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.0-0.1-0.10.0-0.7-0.90.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments us-gaap:CorporateAndOther0.00.00.00.00.00.00.00.0

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

so:AlabamaPower, us-gaap:RetainedEarnings


Net
Period End2021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value359444298280469296217373259225
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic31.635.548.732.335.632.910.432.0-168.224.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.27.76.35.67.55.74.06.14.63.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-8.0-3.01.010.0-3.0-7.0-4.0-9.0-2.03.0-3.03.00.00.02.0-2.01.01.0-1.0
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic-0.7-0.80.11.6-0.3-1.7-0.3-1.0-0.11.1-0.3-1.90.00.00.20.10.20.5-0.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.10.00.00.2-0.1-0.1-0.1-0.2-0.00.1-0.00.10.00.00.0-0.00.00.0-0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination0.00.00.00.00.00.00.00.00.00.06.80.00.00.0-5.00.00.00.00.0

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:ElectricUtilities, so:SouthernPower


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value9726746375238617456-48.09222121
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic8.56.75.910.38.65.66.519.42.7-17.87.9-14.312.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.40.01.31.31.50.51.43.31.0-0.91.50.41.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:ElectricUtilities so:SouthernPower0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, so:ElectricUtilities, so:TraditionalElectricOperatingCompanies


Net
Period End2021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value756128464564213737825651148-48.0
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic66.6102.6105.474.0104.387.027.198.631.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax11.022.313.512.821.915.010.418.6-0.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:ElectricUtilities so:TraditionalElectricOperatingCompanies0.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:SouthernCompanyGas


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-302016-09-30
Value3982301471275238-29.01062707846-31.027915494.0
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic35.159.41.111.631.758.2-2.211.813.029.04.020.129.71.4-3.50.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.80.00.21.55.54.8-0.52.05.01.50.7-0.64.40.20.90.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:SouthernCompanyGas0.00.00.00.00.00.00.00.00.00.09.30.00.02.70.00.0

us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value-108.0-172.0-122.0-177.0-121.0-23.0-110.0-154.0
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic-9.5-44.4-9.8-28.9-13.9-5.6-8.4-17.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.60.0-2.1-3.7-2.4-0.5-1.8-2.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments us-gaap:CorporateAndOther0.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic us-gaap:ProductOrService

so:ElectricUtilities


Net
Period End2021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value853332135870871723314599566213581240-26.0733-1360.0502180119468451430897660751028472261135141185029695380977596369271918603423167819507496
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic75.285.8108.6115.782.657.0110.9106.329.8133.1106.516.978.198.576.391.4105.7111.8106.0113.7101.896.5100.4100.4100.6100.0100.099.399.899.7117.399.2100.195.7100.3103.8100.299.8100.2109.2100.299.4100.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.40.023.614.914.34.723.218.311.56.720.1-0.511.5-25.08.73.519.115.313.08.618.114.012.27.113.513.77.610.516.97.02.410.319.414.310.27.316.913.310.54.415.412.011.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Nonoperating Income Expense

us-gaap:NonoperatingIncomeExpense

us-gaap:NonoperatingIncomeExpense


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-344.0-301.0-422.0-259.0-432.0-277.0-355.0-301.0-266.0-272.0-458.0-329.0-329.0-327.0-470.0-346.0-341.0-326.0-348.0-301.0-277.0-214.0-163.0-179.0-153.0-158.0-156.0-176.0-154.0-169.0-197.0-179.0-178.0-175.0-182.0-216.0-176.0-167.0-185.0-200.0-183.0-178.0-175.0
Percentage of NonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-6.3-4.40.0-4.5-9.1-5.5-7.2-4.8-5.1-5.0-8.6-5.3-5.8-5.1-8.3-5.6-6.3-5.6-6.7-4.8-6.2-5.4-4.6-3.3-3.5-3.8-3.4-4.5-3.1-4.0-5.1-4.8-3.5-4.2-5.0-5.8-3.2-3.7-4.6-5.3-3.4-4.2-4.2

us-gaap:NonoperatingIncomeExpense dei:LegalEntity

so:AlabamaPower


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-39.0-40.0-49.0-42.0-46.0-54.0-67.0-59.0-57.0-55.0-68.0-57.0-54.0-61.0-70.0-70.0-68.0-72.0-78.0-75.0-72.0-71.0-60.0-64.0-69.0-54.0-56.0-45.0-55.0-57.0-75.0-58.0-55.0-59.0-66.0-70.0-69.0-71.0-76.0-69.0-73.0-71.0-76.0-70.0-70.0
Percentage of NonoperatingIncomeExpense11.313.311.616.210.619.518.919.621.420.214.817.316.418.714.920.219.922.122.424.926.033.236.835.845.134.20.00.00.036.542.637.732.529.936.939.339.439.035.239.243.738.438.038.339.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.7-0.60.0-0.7-1.0-1.1-1.4-0.9-1.1-1.0-1.3-0.9-1.0-1.0-1.2-1.1-1.3-1.2-1.5-1.2-1.6-1.8-1.7-1.2-1.6-1.3-1.4-0.8-1.2-1.2-1.9-1.2-1.3-1.5-1.8-1.4-1.7-2.0-2.1-1.3-1.6-1.8-2.0-1.3-1.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower-2.7-2.70.0-2.5-3.5-4.0-4.9-3.2-3.8-3.9-5.2-3.3-3.6-4.1-4.9-4.0-4.6-5.2-5.9-4.2-5.0-5.3-4.9-3.8-4.7-3.9-4.2-2.7-3.8-3.8-5.7-3.6-4.0-4.5-5.1-4.3-5.0-5.8-6.0-4.1-5.1-5.40.0-4.1-4.8

so:GeorgiaPower


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-34.0-32.0-79.0-52.0-54.0-59.0-78.0-67.0-70.0-56.0-83.0-65.0-67.0-68.0-117.0-100.0-88.0-81.0-95.0-87.0-91.0-77.0-64.0-72.0-92.0-74.0-92.0-74.0-79.0-80.0-69.0-82.0-88.0-87.0-85.0-81.0-83.0-81.0-66.0-68.0-54.0-72.0-63.0-66.0-52.0
Percentage of NonoperatingIncomeExpense9.910.618.720.112.521.322.022.326.320.618.119.820.420.824.928.925.824.827.328.932.936.039.340.260.146.80.00.00.051.339.253.252.144.247.545.547.444.530.638.632.338.931.536.129.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.6-0.50.0-0.9-1.1-1.2-1.6-1.1-1.3-1.0-1.6-1.1-1.2-1.1-2.1-1.6-1.6-1.4-1.8-1.4-2.0-1.9-1.8-1.3-2.1-1.8-2.3-1.4-1.8-1.7-1.8-1.6-2.1-2.2-2.3-1.6-2.0-2.2-1.8-1.3-1.2-1.8-1.7-1.2-1.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower-1.6-1.70.0-2.1-2.8-3.2-4.6-2.4-3.4-3.1-4.6-2.5-3.3-3.5-6.2-3.9-4.3-4.4-5.4-3.2-4.4-4.1-3.9-2.7-4.6-3.7-4.8-2.8-3.6-3.5-3.7-3.3-4.3-4.6-4.9-3.2-4.1-4.6-3.8-2.4-2.4-3.60.0-2.5-2.6

so:MississippiPower


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-3.0-6.0-17.0-8.0-9.0-8.0-19.0-13.0-12.0-12.0-28.0-19.06.0-18.0-24.01320153.015141112145415141522242523161410100.6883.94.1553.859-0.753-2.943-2.994-2.248-4.754
Percentage of NonoperatingIncomeExpense0.92.04.03.12.12.95.44.34.54.46.15.8-1.85.55.1-3.8-5.9-4.6-0.9-5.0-5.1-5.1-7.4-7.8-35.3-9.50.00.00.0-15.5-14.3-15.3-9.7-7.2-5.6-6.0-0.4-2.1-1.9-2.20.51.61.51.22.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.1-0.10.0-0.1-0.2-0.2-0.4-0.2-0.2-0.2-0.5-0.30.1-0.3-0.40.20.40.30.10.20.30.30.30.31.20.40.40.30.50.50.60.50.40.40.30.20.00.10.10.1-0.0-0.1-0.1-0.0-0.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower-1.0-2.10.0-2.4-3.3-2.9-6.5-3.4-3.9-4.2-9.1-5.32.0-6.0-8.93.86.65.51.14.35.14.34.94.119.65.46.14.27.37.39.47.25.35.74.23.50.31.71.71.2-0.3-1.10.0-0.7-1.7

so:SouthernCompanyGas


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-125.0-82.0-17.0-12.0-15.0-6.0-12.0-16.0-22.0-6.0-38.0-12.0-25.0-5.0-36.0-1.0-16.0-2.0-6.0-1.0
Percentage of NonoperatingIncomeExpense36.327.24.04.63.52.23.45.38.32.28.33.67.61.57.70.34.70.61.70.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.3-1.20.0-0.2-0.3-0.1-0.2-0.3-0.4-0.1-0.7-0.2-0.4-0.1-0.6-0.0-0.3-0.0-0.1-0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-9.3-2.80.0-1.3-1.5-0.5-1.1-1.8-2.1-0.4-3.6-2.4-3.4-0.3-3.3-0.2-2.2-0.1-0.5-0.2

so:SouthernPower


Nonoperating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value-36.0-31.0-37.0-23.0-37.0-37.0-43.0-37.0-1.0-42.0-44.0-28.0-44.0-44.0-49.0-44.0-46.0-51.0-36.0-33.0-21.0-19.0-15.0-17.0-22.0-22.0-22.076-17.472-21.998-21.885-21.885-13.752-22.259-20.651-18.038-17.732-14.143-13.612-41.515-20.044-18.034-18.77-17.684-19.01-19.866
Percentage of NonoperatingIncomeExpense10.510.38.88.98.613.412.112.30.415.49.68.513.413.510.412.713.515.610.311.07.68.99.29.514.413.90.00.00.014.012.48.913.210.510.110.08.17.519.211.410.810.18.810.411.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.7-0.40.0-0.4-0.8-0.7-0.9-0.6-0.0-0.8-0.8-0.5-0.8-0.7-0.9-0.7-0.8-0.9-0.7-0.5-0.5-0.5-0.4-0.3-0.5-0.5-0.5-0.3-0.5-0.5-0.6-0.3-0.5-0.5-0.5-0.4-0.3-0.4-1.1-0.4-0.4-0.5-0.5-0.4-0.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower-11.4-10.50.0-6.9-13.8-9.9-10.5-9.9-0.3-9.5-8.7-4.4-7.9-8.6-10.3-7.1-8.7-11.3-9.3-6.6-5.6-6.0-4.9-4.2-6.5-6.3-5.7-4.0-6.7-6.2-7.3-3.8-7.2-6.8-6.2-5.0-4.9-5.4-14.5-5.5-5.9-6.70.0-5.3-8.0

Operating Income Loss

us-gaap:OperatingIncomeLoss

us-gaap:OperatingIncomeLoss


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value708159872918351058126369020131342369157821746313767942045-1594.013065871917118593357816491098957561127811037007991491640325814174011437665891652113685447014599519224771415886490
Percentage of OperatingIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax13.123.20.031.922.225.214.032.025.768.210.835.31.121.614.133.0-29.422.611.330.626.623.516.230.525.322.914.023.924.715.120.329.715.18.322.034.527.321.315.930.425.121.312.527.422.622.213.630.222.813.4

us-gaap:OperatingIncomeLoss dei:LegalEntity

so:AlabamaPower


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value478513211620441422134676445338164561380372268616454376252650430333264555398346267520357381312500357307271544390291258523404329204497389
Percentage of OperatingIncomeLoss67.532.128.933.841.733.419.433.633.29.228.425.8603.227.033.830.1-28.528.842.933.936.335.745.733.736.236.247.640.732.454.439.033.555.894.533.331.334.138.043.831.735.638.543.434.140.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax8.87.40.010.89.38.42.710.88.56.23.19.16.85.84.89.98.46.54.910.49.68.47.410.39.28.36.69.78.08.27.910.08.47.97.310.89.38.17.09.68.98.25.49.39.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower33.634.80.037.133.631.29.836.229.924.012.532.225.325.318.735.430.627.219.036.429.825.021.732.727.424.720.131.224.825.323.731.225.623.521.033.228.323.920.331.328.124.90.029.126.6

so:GeorgiaPower


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value1274011979973734062051161647448257991-472.051347010346395012581054656509376964554454288920572516404872552412400924535344222895537393141714411
Percentage of OperatingIncomeLoss17.925.127.054.335.332.129.757.748.212.144.545.6-749.237.359.250.6-40.138.444.055.055.454.665.158.550.547.451.372.051.973.750.658.586.2126.849.153.146.844.937.754.247.346.030.048.943.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.35.80.017.37.88.14.218.512.48.34.816.1-8.48.18.316.711.88.75.016.814.712.810.517.812.810.97.217.212.811.110.317.413.010.610.818.312.89.56.016.511.99.83.713.49.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower6.121.00.039.419.322.212.041.631.324.414.138.2-23.026.224.940.631.227.314.639.132.027.222.935.827.523.015.135.026.222.721.735.127.021.923.137.026.519.712.632.123.719.80.027.220.5

so:MississippiPower


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value495525875046229354565280547.0-177.051-2954.0-62.0-166.09.0-28.0-10.0-143.0-66.01224-70.721-349.0156-325.46-24.412-79.89-388.395-429.1483166463016533925285529
Percentage of OperatingIncomeLoss6.93.43.44.74.73.63.24.64.01.59.03.785.70.5-22.32.5185.3-4.7-28.30.5-2.4-1.1-24.7-4.01.12.5-12.6-27.35.1-46.5-3.1-5.4-60.7-132.03.93.84.13.92.83.23.42.96.03.83.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.90.80.01.51.00.90.41.51.01.01.01.31.00.1-3.10.8-54.4-1.1-3.20.1-0.6-0.3-4.0-1.20.30.6-1.8-6.51.3-7.0-0.6-1.6-9.1-11.00.91.31.10.80.41.00.90.60.71.00.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower16.918.80.026.018.116.67.524.717.419.516.922.318.22.3-65.315.0-974.9-22.8-59.92.6-10.1-3.9-58.1-19.44.48.7-28.8-98.418.0-98.3-9.1-24.6-126.7-174.513.421.717.713.26.916.313.79.60.016.810.7

so:SouthernCompanyGas


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value3160132229102360318-35.013435310437449388110689639118512
Percentage of OperatingIncomeLoss4.437.644.21.69.628.546.1-1.710.09.618.017.277.828.213.93.3-6.029.931.50.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.68.70.00.52.17.26.5-0.62.66.51.96.10.96.12.01.11.86.83.60.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas2.320.20.03.110.328.828.1-3.812.523.99.976.06.723.710.212.013.425.116.72.2

so:SouthernPower


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value70865.013911188151671536030136166032159112652813481475512975674010451595311655646511990566310886776811158
Percentage of OperatingIncomeLoss9.95.40.77.610.57.02.28.311.41.65.26.325.44.44.07.8-7.05.04.87.06.85.09.57.86.87.07.28.24.68.56.77.88.619.98.16.97.97.410.86.67.69.114.67.76.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.31.20.02.42.31.80.32.72.91.10.62.20.30.90.62.62.11.10.52.11.81.21.52.41.71.61.02.01.11.31.42.31.31.71.82.42.21.61.72.01.91.91.82.11.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower22.229.10.041.941.423.53.644.948.613.55.921.42.911.86.725.721.214.47.226.821.714.918.132.222.319.310.424.115.516.917.931.917.921.322.633.631.522.222.230.028.427.40.031.323.7

us-gaap:OperatingIncomeLoss us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

so:SNG, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Operating
Period End2020-09-302020-06-302019-09-302019-06-30
Value85788286
Percentage of OperatingIncomeLoss4.67.44.16.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.51.61.31.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SNG us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.0

Other Comprehensive Income Loss Net Of Tax

us-gaap:OtherComprehensiveIncomeLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value1228-52.0204.0-47.0-42.0-41.0-35.00.0-26.0111230-7.09.0-2.0-9.04522-3.0
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.20.40.00.30.1-0.9-0.9-0.7-0.70.0-0.50.20.20.5-0.10.1-0.0-0.20.90.4-0.1

us-gaap:OtherComprehensiveIncomeLossNetOfTax dei:LegalEntity

so:GeorgiaPower


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value1.02.02.02.02.0-1.019-35.0-27.01.00.01.01.01.01.01.01.01.00.01.01.0
Percentage of OtherComprehensiveIncomeLossNetOfTax8.37.1-3.810.050.02.1-45.285.477.10.0-0.09.18.33.3-14.311.1-50.0-11.10.04.5-33.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.00.00.00.0-0.00.4-0.6-0.50.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower0.00.10.00.10.1-0.11.1-1.3-1.30.10.00.00.00.10.10.00.00.10.00.00.0

so:MississippiPower


Other
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value0.01.00.00.00.00.00.00.00.00.00.0-1.0-1.0-1.00.01.02.00.00.0
Percentage of OtherComprehensiveIncomeLossNetOfTax-0.05.00.0-0.0-0.0-0.0-0.00.0-0.00.00.0-3.314.3-11.1-0.0-11.14.40.0-0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.00.00.00.00.00.00.00.00.00.0-0.0-0.0-0.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower0.00.30.00.00.00.00.00.00.00.00.0-0.3-0.4-0.30.00.40.70.00.0

so:SouthernCompanyGas


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value8.04.0-19.05.00.0-15.0-12.0-3.0-3.0-1.0-7.06.01.02.0-2.00.0-1.0-2.029-3.0
Percentage of OtherComprehensiveIncomeLossNetOfTax66.714.336.525.00.031.928.67.38.60.026.954.58.36.728.60.050.022.264.4-13.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.10.00.10.0-0.3-0.2-0.0-0.1-0.0-0.10.10.00.0-0.00.0-0.0-0.00.6-0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas0.60.10.00.50.0-1.2-1.1-0.3-0.3-0.1-0.71.20.10.1-0.20.0-0.1-0.12.6-0.6

so:SouthernPower


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-30
Value-3.016-14.08.0-3.0-33.0-22.0-8.0-8.0-4.0-14.00.04.0240.05.0-5.0-12.01922-11.0
Percentage of OtherComprehensiveIncomeLossNetOfTax-25.057.126.940.0-75.070.252.419.522.90.053.80.033.380.0-0.055.6250.0133.342.2100.0366.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.10.20.00.1-0.1-0.7-0.4-0.1-0.2-0.1-0.30.00.10.40.00.1-0.1-0.20.40.4-0.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower-0.95.40.02.4-1.1-8.8-5.4-2.2-2.5-0.9-2.80.00.74.70.00.8-0.9-2.74.94.4-2.9

Other Nonoperating Income Expense

us-gaap:OtherNonoperatingIncomeExpense

us-gaap:OtherNonoperatingIncomeExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value108581711310110313619978-81.0577860-57.011-3.0-6.0-55.021-29.0-21.0-21.0-21.0-12.0-8.0-7.0-61.0-10.0-4.0-6.0-50.01.013-2.0-37.0-1.0-4.02.0-67.0-3.0-5.0-2.0
Percentage of OtherNonoperatingIncomeExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.00.80.02.02.12.10.31.01.91.4-1.50.91.40.9-1.00.2-0.1-0.1-1.10.3-0.7-0.5-0.6-0.4-0.3-0.2-0.2-1.6-0.2-0.1-0.2-1.40.00.3-0.1-1.0-0.0-0.10.0-1.8-0.1-0.1-0.0

us-gaap:OtherNonoperatingIncomeExpense dei:LegalEntity

so:AlabamaPower


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value33322230262410.0111114-4.09.0125.0-6.0-5.01.0-5.0-5.0-5.0-4.0-8.0-23.0-7.0-14.0-4.0-17.03.0-3.0-5.0-37.00.02.0-1.0-6.0-7.0-4.0-7.0-10.0-7.0-7.0-6.0-12.0-7.0-5.0
Percentage of OtherNonoperatingIncomeExpense30.655.2129.426.525.723.376.918.011.117.94.915.815.48.310.5-45.5-33.383.39.1-23.813.838.1109.533.3116.750.00.00.00.071.460.7-0.0-50.016.712.0-700.0-30.8350.027.0700.0175.0-300.017.9233.3100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.60.50.00.50.50.50.20.20.20.3-0.10.10.20.1-0.1-0.10.0-0.1-0.1-0.1-0.1-0.2-0.6-0.1-0.3-0.1-0.40.1-0.1-0.1-0.90.00.0-0.0-0.2-0.1-0.1-0.2-0.3-0.1-0.2-0.1-0.3-0.1-0.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower2.32.20.01.82.01.80.70.60.71.0-0.30.50.80.3-0.4-0.30.1-0.4-0.4-0.3-0.3-0.6-1.9-0.4-1.0-0.3-1.30.2-0.2-0.3-2.80.00.1-0.1-0.5-0.4-0.3-0.6-0.8-0.4-0.5-0.50.0-0.4-0.3

so:GeorgiaPower


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value4272245451522736354011303538-8.05.016203.0118.01727181.00.0-22.01.01.0-2.07.0-1.01.0-2.0-7.0-1.0-6.0-3.0-3.0-4.0-5.0-1.0-5.0-5.0-1.0
Percentage of OtherNonoperatingIncomeExpense38.9124.1141.247.850.550.5207.759.035.451.3-13.652.644.963.314.045.5-533.3-333.3-5.552.4-27.6-81.0-128.6-85.7-8.3-0.00.00.00.028.6-11.510.0-25.033.314.0-100.0-46.2150.08.1400.0125.0-50.07.5166.720.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.81.00.00.91.11.00.50.60.70.70.20.50.60.6-0.10.10.30.30.10.20.20.40.80.30.00.0-0.50.00.0-0.00.2-0.00.0-0.1-0.2-0.0-0.1-0.1-0.1-0.1-0.1-0.0-0.1-0.1-0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower2.03.80.02.12.62.81.61.31.72.20.61.21.71.9-0.40.20.81.10.20.40.40.91.60.70.00.0-1.20.00.0-0.10.4-0.00.0-0.1-0.4-0.0-0.3-0.2-0.2-0.1-0.2-0.10.0-0.2-0.1

so:MississippiPower


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value118.0-2.06.06.08.0-3.04.05.05.0-11.00.0271.0-5.0-1.01.0-1.0-3.0-1.0-1.0-2.0-3.0-2.0-1.0-2.0-2.601-7.764-1.933-1.799-2.032-0.375-2.262-1.547-1.1412.441-0.539-0.2420.7140.257-0.613-0.4030.4661.0990.642
Percentage of OtherNonoperatingIncomeExpense10.213.8-11.85.35.97.8-23.16.65.16.413.60.034.61.78.8-9.1-33.316.75.5-4.83.49.514.39.58.325.00.00.00.025.73.33.856.525.82.3244.1-4.112.1-1.9-25.715.3-20.1-0.7-36.6-12.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.20.10.00.10.10.2-0.10.10.10.1-0.20.00.50.0-0.1-0.00.0-0.0-0.1-0.0-0.0-0.1-0.1-0.0-0.0-0.0-0.1-0.1-0.0-0.0-0.1-0.0-0.1-0.0-0.00.0-0.0-0.00.00.0-0.0-0.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower3.82.70.01.82.22.9-1.01.11.61.7-3.60.09.10.3-1.8-0.30.3-0.4-1.1-0.3-0.4-0.8-1.2-0.6-0.4-0.7-1.1-2.2-0.6-0.5-0.8-0.1-0.7-0.6-0.50.8-0.2-0.10.30.1-0.2-0.20.00.30.2

so:SouthernCompanyGas


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-14.0-63.08.012129.04.05.06.05.0-20.06.03.01213183.05.05.09.0
Percentage of OtherNonoperatingIncomeExpense-13.0-108.647.110.611.98.730.88.26.16.424.710.53.820.0-22.8163.6-100.0-83.3-9.142.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.3-0.90.00.20.30.20.10.10.10.1-0.40.10.10.20.20.30.10.10.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-1.0-2.10.01.31.20.70.40.50.60.3-1.91.20.40.71.23.20.40.30.51.7

so:SouthernPower


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value1.07.00.0131.02.0-1.06.0402.01.0172.03.0-2.03.02.0-1.03.02.01.02.00.01.01.00.0-0.0365.511-0.0320.118-1.333-0.791-1.691-0.257-0.336-0.522-0.1940.03-0.864-0.158-0.260.059-0.442-0.209-0.313
Percentage of OtherNonoperatingIncomeExpense0.912.10.011.51.01.9-7.79.840.42.6-1.229.82.65.03.527.3-66.716.7-5.59.5-3.4-9.5-0.0-4.8-8.3-0.00.00.00.0-1.72.27.942.34.30.7-52.2-1.5-1.52.315.86.53.00.77.06.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.10.00.20.00.0-0.00.10.80.00.00.30.00.0-0.00.00.0-0.00.10.00.00.10.00.00.00.0-0.00.1-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.00.0-0.0-0.0-0.00.0-0.0-0.0-0.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower0.32.40.03.90.40.5-0.21.612.70.50.22.70.40.6-0.40.50.4-0.20.80.40.30.60.00.20.30.0-0.01.3-0.00.0-0.4-0.2-0.6-0.1-0.1-0.1-0.10.0-0.3-0.0-0.10.00.0-0.1-0.1

Preferred Stock Dividends Income Statement Impact

us-gaap:PreferredStockDividendsIncomeStatementImpact

us-gaap:PreferredStockDividendsIncomeStatementImpact


Preferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value4.04.04.04.04.04.04.04.03.04.04.04.04.04.06.010.011111111121112111417
Percentage of PreferredStockDividendsIncomeStatementImpact100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.10.00.10.10.10.10.10.10.10.10.10.10.10.10.20.20.20.20.20.30.30.30.20.30.4

us-gaap:PreferredStockDividendsIncomeStatementImpact dei:LegalEntity

so:AlabamaPower


Preferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value4.04.04.04.04.04.04.04.03.04.04.04.03.04.04.05.05.04.04.04.05.04.05.04.07.010.09.010.010.010.09.010.010.010.09.010.010.0
Percentage of PreferredStockDividendsIncomeStatementImpact100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.075.0100.066.750.045.536.436.436.441.736.441.736.450.058.80.00.00.00.00.00.00.00.00.00.00.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.10.00.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.20.20.20.20.20.20.20.20.20.30.20.20.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower0.30.30.00.20.30.30.30.20.20.30.30.20.20.30.30.30.30.30.30.20.30.30.40.20.50.70.70.60.70.70.70.60.70.80.70.60.7

Profit Loss

us-gaap:ProfitLoss

us-gaap:ProfitLoss


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value37611073571283621841409134593120592691222-127.09364991109-1348.0665230116863649729797064352536843186931397399993639384277933620438169834526511
Percentage of ProfitLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.916.00.022.313.016.88.321.417.838.05.019.8-2.314.78.917.9-24.811.54.418.614.312.58.318.014.812.67.911.017.37.42.510.819.715.310.77.517.213.710.94.515.712.512.3

us-gaap:ProfitLoss dei:LegalEntity

so:AlabamaPower


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value335363132448302284924732992217737726222912333023517810935421615912529920717912829218319714926818315112229019513611127420016264269200
Percentage of ProfitLoss89.132.837.034.948.633.822.535.232.110.728.630.9-206.324.524.629.8-17.426.847.430.334.032.042.130.832.234.10.00.00.053.534.630.858.5155.730.629.230.535.440.129.432.337.037.932.338.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.25.30.07.86.35.71.97.55.74.11.46.14.73.62.25.34.33.12.15.74.84.03.55.54.84.33.25.54.14.23.85.34.33.93.35.74.73.83.05.04.44.01.75.14.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower23.624.60.026.823.021.06.725.320.115.75.921.717.415.58.619.015.812.98.219.815.011.910.317.614.212.89.617.512.713.111.316.713.111.59.517.714.211.28.716.413.912.30.015.813.7

so:GeorgiaPower


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value143351164773308331122839448311172664-396.035222758435226412060235227220055528224012752931627021249128720118552930017111452431421058424243
Percentage of ProfitLoss38.031.745.960.249.639.429.862.448.115.163.954.3311.837.645.552.7-26.139.752.251.555.354.767.357.243.945.70.00.00.073.449.256.591.7207.246.453.346.944.541.256.250.647.934.350.846.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.65.10.013.46.56.62.513.48.65.73.210.8-7.05.54.09.46.54.62.39.67.96.95.610.36.55.73.29.97.15.85.49.86.85.25.010.57.24.73.19.76.95.21.58.05.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower6.918.40.030.615.918.17.230.121.717.09.525.6-19.318.012.022.917.214.46.822.317.214.512.220.614.012.16.720.114.511.911.419.814.110.710.721.214.99.86.518.813.910.60.016.112.2

so:MississippiPower


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3845146739320.06537371494747-7.0-555.040-2053.0-20.0-88.0263.011-69.0-21.05035-23.624-194.63762-171.61513-23.682-218.677-245.8883355352516382515163415
Percentage of ProfitLoss10.14.13.95.26.33.80.04.84.01.855.43.8-37.0-0.7-111.23.6152.3-3.0-38.32.20.52.2-23.2-2.27.86.70.00.00.0-46.63.1-2.7-69.9-253.58.45.55.56.76.04.14.13.49.84.13.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.70.01.20.80.60.01.00.70.72.80.80.8-0.1-9.90.6-37.8-0.3-1.70.40.10.3-1.9-0.41.20.8-0.6-3.61.4-3.70.3-0.5-5.2-6.30.91.10.80.70.50.70.60.40.40.60.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower13.115.40.020.014.111.60.017.211.912.948.413.115.8-2.3-204.811.7-677.6-7.4-31.87.41.14.3-28.0-6.218.212.7-9.6-54.920.2-51.85.0-7.3-71.4-100.014.318.013.311.27.011.89.05.70.010.45.7

so:SouthernCompanyGas


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-65.03982301471275238-29.01062707846-31.0279-60.015492391104.0
Percentage of ProfitLoss-17.336.064.41.111.432.758.2-2.211.413.129.03.824.429.8-12.01.4-3.635.947.80.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.25.80.00.21.55.54.8-0.52.05.01.50.7-0.64.4-1.10.20.94.12.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas-4.813.40.01.57.222.021.0-3.29.918.37.49.3-4.217.0-5.62.76.815.39.90.7

so:SouthernPower


Profit
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3665-8.01026844-13.011120327-60.01464511579315410466202031015133111523343653234238527293068462923564437226231
Percentage of ProfitLoss9.65.9-2.28.011.05.2-3.28.321.81.3-22.311.9-35.412.3158.913.9-7.79.98.717.415.910.311.111.48.16.30.00.00.09.35.49.88.930.17.86.97.37.68.66.07.28.613.37.56.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.90.01.81.40.9-0.31.83.90.5-1.12.40.81.814.12.51.91.10.43.22.31.30.92.11.20.81.11.20.70.70.61.70.70.70.81.41.10.80.61.01.00.90.61.20.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower11.422.00.030.725.411.7-3.229.864.46.1-11.923.08.122.6165.924.919.714.75.140.627.116.210.927.715.49.511.315.09.79.87.723.39.19.610.619.316.311.68.315.514.613.40.017.512.7

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

so:GeorgiaPower, us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value143351773308331839448311
Percentage of ProfitLoss38.031.760.249.639.462.448.115.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.65.113.46.56.613.48.65.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

so:MississippiPower, us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value3845673932653737
Percentage of ProfitLoss10.14.15.26.33.84.84.01.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.71.20.80.61.00.70.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-65.03981471275-29.0106270
Percentage of ProfitLoss-17.336.01.111.432.7-2.211.413.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-1.25.80.21.55.5-0.52.05.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

so:SouthernPower, so:CommonStockholdersEquityNotIncludingNoncontrollingInterest


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value36977463758617456
Percentage of ProfitLoss9.68.85.810.18.96.418.72.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.71.41.31.31.51.43.31.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower so:CommonStockholdersEquityNotIncludingNoncontrollingInterest0.00.00.00.00.00.00.00.0

so:SouthernPower, us-gaap:NoncontrollingInterest


Profit
Period End2021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-32.0285.0-31.02529-29.0
Percentage of ProfitLoss-2.92.20.8-3.71.93.1-1.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.50.50.1-0.60.40.6-0.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower us-gaap:NoncontrollingInterest0.00.00.00.00.00.00.0

so:SouthernPower, us-gaap:RetainedEarnings


Profit
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value36977463758617456
Percentage of ProfitLoss9.68.85.810.18.96.418.72.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.71.41.31.31.51.43.31.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

us-gaap:ProfitLoss us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

so:SNG, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Profit
Period End2020-09-302020-06-302019-09-302019-06-30
Value59556064
Percentage of ProfitLoss4.68.94.56.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.01.21.01.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SNG us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.0

Revenue From Contract With Customer Including Assessed Tax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax

us-gaap:RevenueFromContractWithCustomerIncludingAssessedTax


Revenue
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value54226900532657554765501849146282522254125337615956276372562962015430577151816264445939653568540143374183401753394467464439275017424638973703504941813604369654284521401237715320420841573510468238853666
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Revenues

us-gaap:Revenues

us-gaap:Revenues


Revenues
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312009-09-302009-06-302009-03-31
Value51985910511756204620501849145995509854125337615956276372562962015430577151816264445939653568540143374183401753394467464439275017424638973703504941813604369654284521401237715320420841573510468238853666
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax95.985.796.197.797.0100.0100.095.497.6100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues dei:LegalEntity

so:AlabamaPower


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value155615591385172913651351136318411513140813161740150314731433174014841382132917851444133112171695145514011328166914371508131416041392130812901637137712161271167114401320131317061462
Percentage of Revenues29.926.427.130.829.526.927.730.729.726.024.728.326.723.125.528.127.323.925.728.532.433.634.131.433.533.533.131.332.232.533.532.032.833.634.832.432.933.734.430.831.932.934.832.134.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax28.722.626.030.028.626.927.729.329.026.024.728.326.723.125.528.127.323.925.728.532.433.634.131.433.533.533.131.332.232.533.532.032.833.634.832.432.933.734.430.831.932.934.832.134.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower109.5105.70.0103.5104.0100.0100.098.7101.5100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

so:GeorgiaPower


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value222519701938261719281825170327552117183318182593204819611884254620481832176226982051187216412691201619781902263121862269186624842042188217352498202017451758278822651989173726282000
Percentage of Revenues42.833.337.946.641.736.434.746.041.533.934.142.136.430.833.541.137.731.734.043.146.047.246.049.846.547.347.349.348.948.947.549.548.148.346.949.548.348.447.651.450.149.646.149.447.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax41.028.636.445.540.536.434.743.940.533.934.142.136.430.833.541.137.731.734.043.146.047.246.049.846.547.347.349.348.948.947.549.548.148.346.949.548.348.447.651.450.149.646.149.447.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower106.8103.10.0103.599.6100.0100.098.7102.3100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

so:MississippiPower


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-02-252015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value3033072773362832772943703132873083582973022713413032722773522772572463412758.0276245354310331267325306245235305266228237325286263255327276
Percentage of Revenues5.85.25.46.06.15.56.06.26.15.35.85.85.34.74.85.55.64.75.35.66.26.56.96.36.36.60.06.16.67.07.16.86.57.26.36.46.06.46.36.46.06.36.66.86.16.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax5.64.45.25.85.95.56.05.96.05.35.85.85.34.74.85.55.64.75.35.66.26.56.96.36.30.06.66.16.67.07.16.86.57.26.36.46.06.46.36.46.06.36.66.86.16.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower104.5105.10.0100.3102.5100.0100.098.1101.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

so:SouthernCompanyGas


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value6771694107247763612491131498689147410484927301639107956571615601109543
Percentage of Revenues13.028.720.98.513.824.923.08.313.527.219.68.013.025.719.29.113.227.021.48.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.524.620.18.313.324.923.07.913.227.219.68.013.025.719.29.113.227.021.48.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas50.256.90.050.264.2100.0100.054.564.5100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernPower


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value490440396523439375411574510443506635555509478618529450389500373315304401337348386435328350300364307302291354285253286362305281268356248
Percentage of Revenues9.47.47.79.39.57.58.49.610.08.29.510.39.98.08.510.09.77.87.58.08.47.98.57.47.88.39.68.27.47.67.67.37.27.87.97.06.87.07.76.76.87.07.16.75.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax9.06.47.49.19.27.58.49.19.88.29.510.39.98.08.510.09.77.87.58.08.47.98.57.47.88.39.68.27.47.67.67.37.27.87.97.06.87.07.76.76.87.07.16.75.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower155.1148.60.0157.5163.8100.0100.0154.3161.9100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0

us-gaap:Revenues dei:LegalEntity, us-gaap:ConsolidationItems

so:SouthernCompanyGas, us-gaap:IntersegmentElimination


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-6.0-14.0-43.0-6.0-4.0-15.0-19.0-5.0-6.0-32.0-32.0-6.0-5.0-33.0-68.0-44.0-56.0-66.0-57.0-45.0
Percentage of Revenues-0.1-0.2-0.8-0.1-0.1-0.3-0.4-0.1-0.1-0.6-0.6-0.1-0.1-0.5-1.2-0.7-1.0-1.1-1.1-0.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.1-0.2-0.8-0.1-0.1-0.3-0.4-0.1-0.1-0.6-0.6-0.1-0.1-0.5-1.2-0.7-1.0-1.1-1.1-0.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:IntersegmentElimination0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value6721701110347563212561140493682149510644857341671114460776916241165586
Percentage of Revenues12.928.821.68.513.725.023.28.213.427.619.97.913.026.220.39.814.228.122.59.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.424.720.78.313.325.023.27.813.127.619.97.913.026.220.39.814.228.122.59.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments0.00.00.00.00.00.00.00.00.00.00.097.60.00.00.0100.00.00.00.00.0

us-gaap:Revenues dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasDistributionOperations


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value71012008664795871020840448568117288944164312129524726031180887455
Percentage of Revenues13.720.316.98.512.720.317.17.511.121.716.77.211.419.016.97.611.120.417.17.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax13.117.416.38.312.320.317.17.110.921.716.77.211.419.016.97.611.120.417.17.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasDistributionOperations0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasMarketingServices


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value64195136395617713039582291654489271263143166288228126
Percentage of Revenues1.23.32.70.71.23.52.60.71.14.23.10.71.64.34.72.33.15.04.42.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.22.82.60.71.23.52.60.61.14.23.10.71.64.34.72.33.15.04.42.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:GasMarketingServices0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:WholesaleGasServices


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-110.029893-51.0-19.051162-2.048862.0-8.0-16.0166-89.0-24.0-12.013132-8.0
Percentage of Revenues-2.15.01.8-0.9-0.41.03.3-0.00.91.60.0-0.1-0.32.6-1.6-0.4-0.22.30.6-0.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.04.31.7-0.9-0.41.03.3-0.00.91.60.0-0.1-0.32.6-1.6-0.4-0.22.30.6-0.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments so:WholesaleGasServices0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value117.0128.08.08.010.010.013
Percentage of Revenues0.20.10.20.10.20.20.20.20.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.20.10.20.10.20.20.20.20.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:OperatingSegments us-gaap:CorporateAndOther0.00.00.00.00.00.00.00.00.0

us-gaap:Revenues dei:LegalEntity, us-gaap:ProductOrService

so:AlabamaPower, so:WholesaleAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value243210.0117.019152.04.060231431511418
Percentage of Revenues0.50.50.20.20.20.40.30.00.11.10.40.20.60.80.20.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.40.50.20.20.10.40.30.00.11.10.40.20.60.80.20.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower so:WholesaleAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:AlabamaPower, so:WholesaleNonAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value85928573545664716261667465746677
Percentage of Revenues1.61.61.71.31.21.11.31.21.21.11.21.21.21.21.21.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.61.31.61.31.11.11.31.11.21.11.21.21.21.21.21.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower so:WholesaleNonAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:AlabamaPower, us-gaap:ProductAndServiceOther


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value93838070817169746974686869635050
Percentage of Revenues1.81.41.61.21.81.41.41.21.41.41.31.11.21.00.90.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.71.21.51.21.71.41.41.21.31.41.31.11.21.00.90.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower us-gaap:ProductAndServiceOther0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:AlabamaPower, us-gaap:Retail


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1354135212101575122312051215169413781213115915841338128513031595
Percentage of Revenues26.022.923.628.026.524.024.728.327.022.421.725.723.820.223.125.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax25.019.622.727.425.724.024.727.026.422.421.725.723.820.223.125.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:AlabamaPower us-gaap:Retail0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:GeorgiaPower, so:WholesaleNonAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value36433034252642363329644336443945
Percentage of Revenues0.70.70.60.60.50.50.90.60.60.51.20.70.60.70.70.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.70.60.60.60.50.50.90.60.60.51.20.70.60.70.70.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower so:WholesaleNonAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:GeorgiaPower, us-gaap:ProductAndServiceOther


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1631401691481431241431491351331321211201099993
Percentage of Revenues3.12.43.32.63.12.52.92.52.62.52.52.02.11.71.81.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax3.02.03.22.63.02.52.92.42.62.52.52.02.11.71.81.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower us-gaap:ProductAndServiceOther0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:GeorgiaPower, us-gaap:Retail


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2026178717392435176016751526256719461668164024251889179817432402
Percentage of Revenues39.030.234.043.338.133.431.142.838.230.830.739.433.628.231.038.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax37.425.932.742.336.933.431.140.937.330.830.739.433.628.231.038.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GeorgiaPower us-gaap:Retail0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:MississippiPower, so:WholesaleAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2533293625212351372210.02819341621
Percentage of Revenues0.50.60.60.60.50.40.50.90.70.40.20.50.30.50.30.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.50.50.50.60.50.40.50.80.70.40.20.50.30.50.30.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower so:WholesaleAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:MississippiPower, so:WholesaleNonAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value54635161525159645757667059686372
Percentage of Revenues1.01.11.01.11.11.01.21.11.11.11.21.11.01.11.11.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.00.91.01.11.11.01.21.01.11.11.21.11.01.11.11.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower so:WholesaleNonAffiliates0.00.00.00.00.00.00.00.00.00.00.0107.70.00.00.0100.0

so:MississippiPower, us-gaap:ProductAndServiceOther


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value5.07.06.07.07.06.04.04.04.05.0-9.0117.06.04.05.0
Percentage of Revenues0.10.10.10.10.20.10.10.10.10.1-0.20.20.10.10.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.10.10.10.10.10.10.10.10.1-0.20.20.10.10.10.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower us-gaap:ProductAndServiceOther0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:MississippiPower, us-gaap:Retail


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value219204191232199199208251215203229254212194189243
Percentage of Revenues4.23.53.74.14.34.04.24.24.23.84.34.13.83.03.43.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.03.03.64.04.24.04.24.04.13.84.34.13.83.03.43.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:MississippiPower us-gaap:Retail0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:SouthernCompanyGas, us-gaap:AlternativeEnergy


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value2.02.0-3.0-1.0-2.09.0-1.00.01.0-2.03.05.0-4.0-24.0-5.00.0
Percentage of Revenues0.00.0-0.1-0.0-0.00.2-0.00.00.0-0.00.10.1-0.1-0.4-0.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.0-0.1-0.0-0.00.2-0.00.00.0-0.00.10.1-0.1-0.4-0.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:AlternativeEnergy0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.00.0

so:SouthernCompanyGas, us-gaap:NaturalGasUsRegulated


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value67516921075478638124011324986881476104548771016311050532
Percentage of Revenues13.028.621.08.513.824.723.08.313.527.319.67.912.625.618.78.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.424.520.28.313.424.723.07.913.227.319.67.912.625.618.78.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas us-gaap:NaturalGasUsRegulated0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:SouthernPower, so:WholesaleAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value1128185101928678116117871091341098397105
Percentage of Revenues2.21.41.71.82.01.71.61.92.31.62.02.21.91.31.71.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.11.21.61.81.91.71.61.82.21.62.02.21.91.31.71.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower so:WholesaleAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:SouthernPower, so:WholesaleNonAffiliates


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value373355308418343286331455390352394496443424378510
Percentage of Revenues7.26.06.07.47.45.76.77.67.76.57.48.17.96.76.78.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax6.95.15.87.37.25.76.77.27.56.57.48.17.96.76.78.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower so:WholesaleNonAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:SouthernPower, us-gaap:ProductAndServiceOther


Revenuesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value5.04.03.04.04.03.02.03.03.04.03.05.03.02.03.03.0
Percentage of Revenues0.10.10.10.10.10.10.00.10.10.10.10.10.10.00.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.10.10.10.10.10.10.00.00.10.10.10.10.10.00.10.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernPower us-gaap:ProductAndServiceOther0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

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

so:SouthernCompanyGas, so:WholesaleGasServices


Revenuesdei:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value-110.0298-51.0-19.051-2.048
Percentage of Revenues-2.15.0-0.9-0.41.0-0.00.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.04.3-0.9-0.41.0-0.00.9
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas so:WholesaleGasServices0.00.00.00.00.00.00.0

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

so:SouthernCompanyGas, so:WholesaleGasServices, so:IntercompanyRevenues


Revenuesdei:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value27633318297263
Percentage of Revenues0.51.10.60.40.61.21.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.50.90.60.40.61.11.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas so:WholesaleGasServices so:IntercompanyRevenues0.00.00.00.00.00.00.0

so:SouthernCompanyGas, so:WholesaleGasServices, so:ThirdPartyGrossRevenues


Revenuesdei:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value129225881050854118511381223
Percentage of Revenues24.943.818.718.523.619.024.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax23.837.518.217.923.618.123.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas so:WholesaleGasServices so:ThirdPartyGrossRevenues0.00.00.00.00.00.00.0

so:SouthernCompanyGas, so:WholesaleGasServices, so:TotalGrossRevenues


Revenuesdei:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-30
Value131926511083872121412101286
Percentage of Revenues25.444.919.318.924.220.225.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax24.338.418.818.324.219.324.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas so:WholesaleGasServices so:TotalGrossRevenues0.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-40.0-35.0-40.0-38.0-35.0-40.0-40.0-12.0-67.0-39.0-55.0-44.0-49.0-50.0-51.0-40.0-37.0-43.0-42.0-37.0
Percentage of Revenues-0.8-0.6-0.8-0.7-0.8-0.8-0.8-0.2-1.3-0.7-1.0-0.7-0.9-0.8-0.9-0.6-0.7-0.7-0.8-0.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-0.7-0.5-0.8-0.7-0.7-0.8-0.8-0.2-1.3-0.7-1.0-0.7-0.9-0.8-0.9-0.6-0.7-0.7-0.8-0.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.00.0

us-gaap:Revenues us-gaap:ConsolidationItems, us-gaap:ProductOrService

us-gaap:IntersegmentElimination, so:ElectricUtilities


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-30
Value-114.0-87.0-86.0-103.0-94.0-87.0-81.0-119.0-119.0-93.0-117.0-140.0-114.0-106.0-101.0-105.0-109.0-117.0-109.0-103.0-117.0-109.0-90.0-124.0-148.0-115.0
Percentage of Revenues-2.2-1.5-1.7-1.8-2.0-1.7-1.6-2.0-2.3-1.7-2.2-2.3-2.0-1.7-1.9-1.8-2.1-1.9-2.4-2.6-3.3-2.0-2.1-3.0-3.7-2.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.1-1.3-1.6-1.8-2.0-1.7-1.6-1.9-2.3-1.7-2.2-2.3-2.0-1.7-1.9-1.8-2.1-1.9-2.4-2.6-3.3-2.0-2.1-3.0-3.7-2.2
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:IntersegmentElimination so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:ElectricUtilities, so:SouthernPower


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value490440396523439375411574510443506635555509
Percentage of Revenues9.47.47.79.39.57.58.49.610.08.29.510.39.98.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax9.06.47.49.19.27.58.49.19.88.29.510.39.98.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:ElectricUtilities so:SouthernPower0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OperatingSegments, so:ElectricUtilities, so:TraditionalElectricOperatingCompanies


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value4031376446293539340749083899344550144124
Percentage of Revenues77.563.782.476.667.981.976.563.781.473.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax74.354.680.474.367.978.174.763.781.473.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:ElectricUtilities so:TraditionalElectricOperatingCompanies0.00.00.00.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:SouthernCompanyGas


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-09-302017-06-302016-09-30
Value6771694107247763612491131498689147410484927301639565716543
Percentage of Revenues13.028.720.98.513.824.923.08.313.527.219.68.013.025.79.113.28.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.524.620.18.313.324.923.07.913.227.219.68.013.025.79.113.28.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments so:SouthernCompanyGas0.00.00.00.00.00.00.00.00.00.00.0100.00.00.0100.00.00.0

us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-30
Value154134216132135114176146186
Percentage of Revenues3.02.34.22.32.92.33.62.43.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.81.94.12.32.82.33.62.33.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:OperatingSegments us-gaap:CorporateAndOther0.00.00.00.00.00.00.00.00.0

us-gaap:Revenues us-gaap:ProductOrService

so:ElectricUtilities


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value44074117386950493884369536475363429037954115550945654382458541313962561943793954355553904324417239985327445446273915500542303885369050334166358936795411450339943752529941874136
Percentage of Revenues84.869.775.689.884.173.674.289.584.270.177.189.481.168.884.471.676.589.798.299.799.699.899.799.799.599.899.799.699.799.899.699.799.699.799.699.699.599.799.699.699.599.699.599.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax81.359.772.687.781.573.674.285.482.270.177.189.481.168.884.471.676.589.798.299.799.699.899.799.799.599.899.799.699.799.899.699.799.699.799.699.699.599.799.699.699.599.699.599.5
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:OtherElectricRevenue


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value175170188164168151144163161168169165170161274168
Percentage of Revenues3.42.93.72.93.63.02.92.73.23.13.22.73.02.54.92.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax3.22.53.52.83.53.02.92.63.13.13.22.73.02.54.92.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:OtherElectricRevenue0.00.00.00.00.00.00.00.00.00.00.097.10.00.00.0100.0

so:WholesaleNonAffiliates


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value546545472584472418485625542499579698616623559718
Percentage of Revenues10.59.29.210.410.28.39.910.410.69.210.811.310.99.89.911.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax10.17.98.910.19.98.39.99.910.49.210.811.310.99.89.911.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:WholesaleNonAffiliates0.00.00.00.00.00.00.00.00.00.00.0100.70.00.00.0100.0

us-gaap:AlternativeEnergy


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value2.02.0-1.0-2.09.00.01.0-2.05.0-4.0-24.00.0
Percentage of Revenues0.00.0-0.0-0.00.20.00.0-0.00.1-0.1-0.40.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.00.0-0.0-0.00.20.00.0-0.00.1-0.1-0.40.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:AlternativeEnergy0.00.00.00.00.00.0100.0100.0100.0100.0100.00.0

us-gaap:NaturalGasUsRegulated


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value67716941072477636124911314986891474104849270616071045532
Percentage of Revenues13.028.720.98.513.824.923.08.313.527.219.68.012.525.218.68.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.524.620.18.313.324.923.07.913.227.219.68.012.525.218.68.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:NaturalGasUsRegulated0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

us-gaap:ProductAndServiceOther


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value201159245152162122206197166187-277.0369395413309168
Percentage of Revenues3.92.74.82.73.52.44.23.33.33.5-5.26.07.06.55.52.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax3.72.34.62.63.42.44.23.13.23.5-5.26.07.06.55.52.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:ProductAndServiceOther0.00.00.00.00.00.00.00.00.00.00.0185.40.00.00.0100.0

us-gaap:Retail


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value3599334231404243318230782948451235403084330946053740356835444615
Percentage of Revenues69.256.561.475.568.961.360.075.369.457.062.074.866.556.063.074.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax66.448.459.073.766.861.360.071.867.857.062.074.866.556.063.074.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:Retail0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

us-gaap:Revenues us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

so:GasMarketingServices, so:SouthernCompanyGas


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value64195136395617713039582291654489271263143
Percentage of Revenues1.23.32.70.71.23.52.60.71.14.23.10.71.64.34.72.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax1.22.82.60.71.23.52.60.61.14.23.10.71.64.34.72.3
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:GasMarketingServices so:SouthernCompanyGas0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

so:NaturalGasDistribution, so:SouthernCompanyGas


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value7061192476583101344556311614386381200
Percentage of Revenues13.620.28.512.620.27.411.021.57.111.318.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax13.017.38.312.220.27.110.821.57.111.318.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:NaturalGasDistribution so:SouthernCompanyGas0.00.00.00.00.00.00.00.00.00.00.0

so:NaturalGasDistributionOther, so:SouthernCompanyGas


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value179.013168.014688410.03.0168
Percentage of Revenues0.30.20.20.30.20.21.31.60.20.12.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax0.30.10.20.30.20.21.31.60.20.12.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:NaturalGasDistributionOther so:SouthernCompanyGas0.00.00.00.00.00.00.00.00.00.00.0

so:OtherElectricRevenue, so:ElectricUtilities


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value262230257222230199214226208212227206209191
Percentage of Revenues5.03.95.04.05.04.04.43.84.13.94.33.33.73.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax4.83.34.83.94.84.04.43.64.03.94.33.33.73.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:OtherElectricRevenue so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

so:WholesaleGasServices, so:SouthernCompanyGas


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-110.0298-51.0-19.051-2.04886
Percentage of Revenues-2.15.0-0.9-0.41.0-0.00.91.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax-2.04.3-0.9-0.41.0-0.00.91.6
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:WholesaleGasServices so:SouthernCompanyGas0.00.00.00.00.00.00.00.0

so:WholesaleNonAffiliates, so:ElectricUtilities


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value546545584472418625542499698616623
Percentage of Revenues10.59.210.410.28.310.410.69.211.310.99.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax10.17.910.19.98.39.910.49.211.310.99.8
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:WholesaleNonAffiliates so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Retail, so:ElectricUtilities


Revenuesus-gaap:
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value359933424243318230782948451235403084330946053740356835444615
Percentage of Revenues69.256.575.568.961.360.075.369.457.062.074.866.556.063.074.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax66.448.473.766.861.360.071.867.857.062.074.866.556.063.074.4
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax us-gaap:Retail so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

us-gaap:Revenues us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName, us-gaap:EquityMethodInvestmentNonconsolidatedInvestee

so:SNG, us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees


Revenuesus-gaap:
Period End2020-09-302020-06-302019-09-302019-06-30
Value150149152155
Percentage of Revenues2.73.22.53.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax2.63.12.43.0
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SNG us-gaap:EquityMethodInvestmentNonconsolidatedInvesteeOrGroupOfInvestees0.00.00.00.0

us-gaap:Revenues us-gaap:StatementBusinessSegments

so:ElectricUtilities


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-09-30
Value4407411738695049388436953647536342903795411555094565438243015523458541315619
Percentage of Revenues84.869.775.689.884.173.674.289.584.270.177.189.481.168.876.489.184.471.689.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax81.359.772.687.781.573.674.285.482.270.177.189.481.168.876.489.184.471.689.7
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:ElectricUtilities0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.00.00.00.0

so:SouthernCompanyGas


Revenuesus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value67716941072477636124911314986891474104849273016391079565
Percentage of Revenues13.028.720.98.513.824.923.08.313.527.219.68.013.025.719.29.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax12.524.620.18.313.324.923.07.913.227.219.68.013.025.719.29.1
Percentage of RevenueFromContractWithCustomerIncludingAssessedTax so:SouthernCompanyGas0.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.0100.0

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value12590712539312293512315811973111885211870011759111486711409611691411171711277711156711100511031510868410976010969710636290873787357831875215741817161070923676546640064838645466469763961632746314961963608975987459267573435602355019550325204648347
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets dei:LegalEntity

so:AlabamaPower


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value316913120530803309693012629368291522901928067274072673026610262702431723864237892313322869225162245722156219772172121633212202075620552202931953019362192511935218838187691871218826185541866418477185151823017994
Percentage of Assets25.224.925.125.125.224.724.624.724.424.022.923.823.321.821.521.621.320.820.521.124.427.927.728.828.629.029.030.029.429.929.829.929.529.729.630.430.531.231.232.332.532.7
Percentage of Assets25.224.925.125.125.224.724.624.724.424.022.923.823.321.821.521.621.320.820.521.124.427.927.728.828.629.029.030.029.429.929.829.929.529.729.630.430.531.231.232.332.532.7
Percentage of Assets so:AlabamaPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:GeorgiaPower


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value476254734947080470464582545179445414441543239425384036536861359613719936779371063618835248348353424834015328023286531726317483151631030299152966929189289072920729127289952880328421280782733727151267052646925914
Percentage of Assets37.837.838.338.238.338.037.537.837.637.334.533.031.933.333.133.633.332.131.832.237.441.742.042.242.844.043.844.244.745.044.845.145.545.845.645.946.145.745.846.647.247.1
Percentage of Assets37.837.838.338.238.338.037.537.837.637.334.533.031.933.333.133.633.332.131.832.237.441.742.042.242.844.043.844.244.745.044.845.145.545.845.645.946.145.745.846.647.247.1
Percentage of Assets so:GeorgiaPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:MississippiPower


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value541248954912484848214860503549464874478548864817465347124866505555318088823581657987791678407913794769476756631163645827584854725438540554515119461443223671284025722476
Percentage of Assets4.33.94.03.94.04.14.24.24.24.24.24.34.14.24.44.65.17.47.57.78.810.110.010.510.79.79.59.39.69.09.18.58.58.58.68.37.67.26.25.04.64.5
Percentage of Assets4.33.94.03.94.04.14.24.24.24.24.24.34.14.24.44.65.17.47.57.78.810.110.010.510.79.79.59.39.69.09.18.58.58.58.68.37.67.26.25.04.64.5
Percentage of Assets so:MississippiPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value23235233772263021932215002161721687210472076120952214482039822112225682298722190218092168321853
Percentage of Assets18.518.618.417.818.018.218.317.918.118.418.318.319.620.220.720.120.119.819.9
Percentage of Assets18.518.618.417.818.018.218.317.918.118.418.318.319.620.220.720.120.119.819.9
Percentage of Assets so:SouthernCompanyGas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernPower


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value137081399513235134241355713646143001439714518151041488315355154281518215206146481470314681151691235111082899989057040622655645549460846054403442944494139385837793781378535963580375735363437
Percentage of Assets10.911.210.810.911.311.512.012.212.613.212.713.713.713.613.713.313.513.413.811.612.211.411.49.48.47.87.86.86.96.86.96.96.56.16.06.16.26.06.06.66.36.2
Percentage of Assets10.911.210.810.911.311.512.012.212.613.212.713.713.713.613.713.313.513.413.811.612.211.411.49.48.47.87.86.86.96.86.96.96.56.16.06.16.26.06.06.66.36.2
Percentage of Assets so:SouthernPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets dei:LegalEntity, us-gaap:ConsolidatedEntities, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

so:SouthernPower, us-gaap:VariableInterestEntityPrimaryBeneficiary, so:OtherVariableInterestEntities


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value1900190011001100150011001100
Percentage of Assets1.51.50.90.91.30.90.9
Percentage of Assets1.51.50.90.91.30.90.9
Percentage of Assets so:SouthernPower us-gaap:VariableInterestEntityPrimaryBeneficiary so:OtherVariableInterestEntities100.0100.0100.0100.0100.0100.0100.0

so:SouthernPower, us-gaap:VariableInterestEntityPrimaryBeneficiary, so:SPSolarHoldingsILP


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value6200610061006300620063006400
Percentage of Assets4.94.95.05.15.25.35.4
Percentage of Assets4.94.95.05.15.25.35.4
Percentage of Assets so:SouthernPower us-gaap:VariableInterestEntityPrimaryBeneficiary so:SPSolarHoldingsILP100.0100.0100.0100.0100.0100.0100.0

so:SouthernPower, us-gaap:VariableInterestEntityPrimaryBeneficiary, so:SPWind


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value2300240024002400240025002500
Percentage of Assets1.81.92.01.92.02.12.1
Percentage of Assets1.81.92.01.92.02.12.1
Percentage of Assets so:SouthernPower us-gaap:VariableInterestEntityPrimaryBeneficiary so:SPWind100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets dei:LegalEntity, us-gaap:ConsolidationItems

so:SouthernCompanyGas, us-gaap:IntersegmentElimination


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value-12095.0-12349.0-11746.0-11482.0-11155.0-11455.0-11300.0-11023.0-11533.0-11540.0-11582.0-11272.0-12783.0-12913.0-14039.0-13262.0-13093.0-12877.0-14167.0
Percentage of Assets-9.6-9.8-9.6-9.3-9.3-9.6-9.5-9.4-10.0-10.1-9.9-10.1-11.3-11.6-12.6-12.0-12.0-11.7-12.9
Percentage of Assets-9.6-9.8-9.6-9.3-9.3-9.6-9.5-9.4-10.0-10.1-9.9-10.1-11.3-11.6-12.6-12.0-12.0-11.7-12.9
Percentage of Assets so:SouthernCompanyGas us-gaap:IntersegmentElimination100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas, us-gaap:OperatingSegments


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value24030242492304022435220102197822228216412136021592219182152423351236422484224052237202370024875
Percentage of Assets19.119.318.718.218.418.518.718.418.618.918.719.320.721.222.421.821.821.622.7
Percentage of Assets19.119.318.718.218.418.518.718.418.618.918.719.320.721.222.421.821.821.622.7
Percentage of Assets so:SouthernCompanyGas us-gaap:OperatingSegments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets dei:LegalEntity, us-gaap:ConsolidationItems, us-gaap:StatementBusinessSegments

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasDistributionOperations


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value20245201611909018715182761816618204177981739717379172661685018654183321935818711182571820119453
Percentage of Assets16.116.115.515.215.315.315.315.115.115.214.815.116.516.417.417.016.816.617.7
Percentage of Assets16.116.115.515.215.315.315.315.115.115.214.815.116.516.417.417.016.816.617.7
Percentage of Assets so:SouthernCompanyGas us-gaap:OperatingSegments so:GasDistributionOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasMarketingServices


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value1486155315031461148015171496144315271611158715221610214421472089209321182084
Percentage of Assets1.21.21.21.21.21.31.31.21.31.41.41.41.41.91.91.91.91.91.9
Percentage of Assets1.21.21.21.21.21.31.31.21.31.41.41.41.41.91.91.91.91.91.9
Percentage of Assets so:SouthernCompanyGas us-gaap:OperatingSegments so:GasMarketingServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:GasPipelineInvestments


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312016-12-31
Value1492159615971609161716521678174317681781176316991659
Percentage of Assets1.21.31.31.31.41.41.41.51.51.61.51.51.5
Percentage of Assets1.21.31.31.31.41.41.41.51.51.61.51.51.5
Percentage of Assets so:SouthernCompanyGas us-gaap:OperatingSegments so:GasPipelineInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, so:WholesaleGasServices


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value8079398506506376438506576688211302855818903109689398910181127
Percentage of Assets0.60.70.70.50.50.50.70.60.60.71.10.80.70.81.00.80.90.91.0
Percentage of Assets0.60.70.70.50.50.50.70.60.60.71.10.80.70.81.00.80.90.91.0
Percentage of Assets so:SouthernCompanyGas us-gaap:OperatingSegments so:WholesaleGasServices100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas, us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Assetsdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312018-12-31
Value11300114771133610979106451075911112
Percentage of Assets9.09.29.28.98.99.19.5
Percentage of Assets9.09.29.28.98.99.19.5
Percentage of Assets so:SouthernCompanyGas us-gaap:OperatingSegments us-gaap:CorporateAndOther100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems

us-gaap:IntersegmentElimination


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-312015-12-312014-12-312013-12-31
Value-736.0-787.0-904.0-861.0-1096.0-948.0-1148.0-1159.0-1286.0-1370.0-1778.0-1869.0-1791.0-1547.0-1619.0-1532.0-1624.0-1061.0-312.0-304.0
Percentage of Assets-0.6-0.6-0.7-0.7-0.9-0.8-1.0-1.0-1.1-1.2-1.5-1.7-1.6-1.4-1.5-1.4-1.5-1.4-0.4-0.5
Percentage of Assets-0.6-0.6-0.7-0.7-0.9-0.8-1.0-1.0-1.1-1.2-1.5-1.7-1.6-1.4-1.5-1.4-1.5-1.4-0.4-0.5
Percentage of Assets us-gaap:IntersegmentElimination100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems, us-gaap:ProductOrService

us-gaap:IntersegmentElimination, so:ElectricUtilities


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302014-12-312013-12-31
Value-693.0-637.0-680.0-671.0-713.0-695.0-713.0-756.0-783.0-779.0-306.0-325.0-317.0-306.0-316.0-440.0-425.0-396.0-397.0-404.0-131.0-101.0
Percentage of Assets-0.6-0.5-0.6-0.5-0.6-0.6-0.6-0.6-0.7-0.7-0.3-0.3-0.3-0.3-0.3-0.4-0.5-0.5-0.5-0.5-0.2-0.2
Percentage of Assets-0.6-0.5-0.6-0.5-0.6-0.6-0.6-0.6-0.7-0.7-0.3-0.3-0.3-0.3-0.3-0.4-0.5-0.5-0.5-0.5-0.2-0.2
Percentage of Assets us-gaap:IntersegmentElimination so:ElectricUtilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidationItems, us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

us-gaap:OperatingSegments, so:ElectricUtilities, so:SouthernPower


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value1370813995132351342413557136461430014397145181510414883
Percentage of Assets10.911.210.810.911.311.512.012.212.613.212.7
Percentage of Assets10.911.210.810.911.311.512.012.212.613.212.7
Percentage of Assets us-gaap:OperatingSegments so:ElectricUtilities so:SouthernPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, so:ElectricUtilities, so:TraditionalElectricOperatingCompanies


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value87330860538548685218831588176581063804937831479382
Percentage of Assets69.468.669.569.269.568.868.368.568.267.9
Percentage of Assets69.468.669.569.269.568.868.368.568.267.9
Percentage of Assets us-gaap:OperatingSegments so:ElectricUtilities so:TraditionalElectricOperatingCompanies100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, so:ElectricUtilities, so:TraditionalOperatingCompanies


Assetsus-gaap:
Period End2020-12-312019-12-312019-03-312018-12-31
Value85486810637679879382
Percentage of Assets69.568.367.367.9
Percentage of Assets69.568.367.367.9
Percentage of Assets us-gaap:OperatingSegments so:ElectricUtilities so:TraditionalOperatingCompanies100.0100.0100.0100.0

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

us-gaap:OperatingSegments, so:SouthernCompanyGas


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302016-12-31
Value2323523377226302193221500216172168721047207612095221448203982211222568229872219021853
Percentage of Assets18.518.618.417.818.018.218.317.918.118.418.318.319.620.220.720.119.9
Percentage of Assets18.518.618.417.818.018.218.317.918.118.418.318.319.620.220.720.119.9
Percentage of Assets us-gaap:OperatingSegments so:SouthernCompanyGas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OperatingSegments, us-gaap:CorporateAndOther


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-312018-12-31
Value3063339231684116332535113285
Percentage of Assets2.42.72.63.32.83.02.8
Percentage of Assets2.42.72.63.32.83.02.8
Percentage of Assets us-gaap:OperatingSegments us-gaap:CorporateAndOther100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ProductOrService

so:ElectricUtilities


Assetsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312017-12-312017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-312008-12-31
Value10034599411980419797196002947169465094134920499112393959870858588987067869948335981363778437756074386733117082170063668626568364160637756402863194625016225161486603855921358076565465554654525542935130347468
Percentage of Assets79.779.379.879.580.279.779.780.180.179.980.478.579.079.379.378.489.598.999.098.998.898.998.898.898.999.098.899.098.898.898.699.299.298.998.098.699.199.198.798.698.2
Percentage of Assets79.779.379.879.580.279.779.780.180.179.980.478.579.079.379.378.489.598.999.098.998.898.998.898.898.999.098.899.098.898.898.699.299.298.998.098.699.199.198.798.698.2
Percentage of Assets so:ElectricUtilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value928709203490410903678747986645866508550983445831188758483328857618521885153839568327482482828038001567262563895617549583446374440744788447904415543770422424169141093406073862837959374723774836086
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets73.873.473.573.473.172.973.072.772.672.874.974.676.076.476.776.176.675.175.575.274.071.671.769.968.868.869.270.069.869.368.268.568.668.567.467.868.168.669.3

us-gaap:Liabilities dei:LegalEntity

so:AlabamaPower


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value207632038820702207632016519468199061964218947183961896218734185781669116744163981614515947159121577415651154971544815352150901428214115138461323713114130641306512687126691262912583124681262912450122321207211916
Percentage of Liabilities22.422.222.923.023.122.523.023.022.722.121.722.521.719.619.719.519.419.319.219.723.327.527.50.00.00.028.50.00.029.429.429.228.328.728.929.829.930.730.731.731.831.6
Percentage of Assets16.516.316.816.916.816.416.816.716.516.116.216.816.515.015.114.914.914.514.514.817.219.719.720.420.319.919.920.519.920.220.220.219.820.020.020.320.521.121.021.321.521.7
Percentage of Assets so:AlabamaPower65.565.367.267.066.966.368.367.767.567.170.970.470.768.670.268.969.869.770.770.270.670.571.171.071.168.868.768.267.867.767.967.567.367.567.566.867.267.767.466.166.266.2

so:GeorgiaPower


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value310793057530579303403038829667294762965128923282692604223010232592377924848248332420923332232132271722814216472188020705210292084420343196221968119288190501934219533194711926418776187461808917862171201719916907
Percentage of Liabilities33.533.233.833.634.734.234.034.734.734.029.727.627.127.929.229.629.128.328.028.433.938.438.90.00.00.041.00.00.043.242.943.243.644.144.044.445.044.044.044.345.344.8
Percentage of Assets24.724.424.924.625.425.024.825.225.224.822.320.620.621.322.422.522.321.321.221.425.127.527.927.528.329.128.729.029.629.729.529.930.530.830.530.330.830.230.129.930.730.7
Percentage of Assets so:GeorgiaPower65.364.665.064.566.365.766.266.866.966.564.562.464.763.967.666.966.966.266.666.367.166.066.665.366.266.165.665.666.366.165.966.267.167.266.966.166.866.265.864.165.065.2

so:MississippiPower


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value356330473170308830973138338333073257317532773341322233283475310836255129525955045353551054485577566647174639425741613843363837083856381236213570324530892589185516981706
Percentage of Liabilities3.83.33.53.43.53.63.93.93.93.83.74.03.83.94.13.74.46.26.46.98.09.89.70.00.00.09.40.00.08.68.28.38.68.68.38.57.87.56.44.84.54.5
Percentage of Assets2.82.42.62.52.62.62.92.82.82.82.83.02.93.03.12.83.34.74.85.25.97.07.07.47.66.66.56.36.35.95.65.76.06.05.75.85.35.24.43.23.03.1
Percentage of Assets so:MississippiPower65.862.264.563.764.264.667.266.966.866.467.169.469.270.671.461.565.563.463.967.467.069.669.570.571.367.968.767.565.466.062.267.870.970.566.469.770.371.570.565.366.068.9

so:SouthernCompanyGas


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value13306132831286312247117311198612181116541200212214128781177513051133691396513023125671243912744
Percentage of Liabilities14.314.414.213.613.413.814.113.614.414.714.714.115.215.716.415.515.115.115.4
Percentage of Assets10.610.610.59.99.810.110.39.910.410.711.010.511.612.012.611.811.611.311.6
Percentage of Assets so:SouthernCompanyGas57.356.856.855.854.655.456.255.457.858.360.057.759.059.260.858.757.657.458.3

so:SouthernPower


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value701872516604681368987095767877047700788675998054785486248708874688388815933078737437571155984289406535523538297830072811283628482602232622492252229421232108228921092171
Percentage of Liabilities7.67.97.37.57.98.28.99.09.29.58.79.79.210.110.210.410.610.711.39.811.110.110.00.00.00.07.10.00.06.36.46.45.85.35.15.35.55.25.25.95.65.8
Percentage of Assets5.65.85.45.55.86.06.56.66.76.96.57.27.07.77.87.98.18.08.57.48.27.37.15.75.55.05.04.44.54.34.44.44.13.73.63.63.83.53.64.03.83.9
Percentage of Assets so:SouthernPower51.251.849.950.850.952.053.753.553.052.251.152.550.956.857.359.760.160.061.563.767.163.562.960.965.363.863.864.665.363.964.064.062.960.359.559.660.659.058.960.959.663.2

us-gaap:Liabilities dei:LegalEntity, us-gaap:ConsolidatedEntities, us-gaap:ScheduleOfEquityMethodInvestmentEquityMethodInvesteeName

so:SouthernPower, us-gaap:VariableInterestEntityPrimaryBeneficiary, so:OtherVariableInterestEntities


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value249260110109160109104
Percentage of Liabilities0.30.30.10.10.20.10.1
Percentage of Assets0.20.20.10.10.10.10.1
Percentage of Assets so:SouthernPower us-gaap:VariableInterestEntityPrimaryBeneficiary so:OtherVariableInterestEntities13.113.710.09.910.79.99.5

so:SouthernPower, us-gaap:VariableInterestEntityPrimaryBeneficiary, so:SPSolarHoldingsILP


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value382377387382381382381
Percentage of Liabilities0.40.40.40.40.40.40.4
Percentage of Assets0.30.30.30.30.30.30.3
Percentage of Assets so:SouthernPower us-gaap:VariableInterestEntityPrimaryBeneficiary so:SPSolarHoldingsILP6.26.26.36.16.16.16.0

so:SouthernPower, us-gaap:VariableInterestEntityPrimaryBeneficiary, so:SPWind


Liabilitiesdei:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value140171138129125123128
Percentage of Liabilities0.20.20.20.10.10.10.1
Percentage of Assets0.10.10.10.10.10.10.1
Percentage of Assets so:SouthernPower us-gaap:VariableInterestEntityPrimaryBeneficiary so:SPWind6.17.15.85.45.24.95.1

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value12590712539312293512315811973111885211870011759111486711409611691411171711277711156711100511031510868410976010969710636290873787357831870923648386454664697639616327463149619636089759874592675734356023550195503252046
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

us-gaap:LiabilitiesAndStockholdersEquity dei:LegalEntity

so:AlabamaPower


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value316913120530803309693012629368291522901928067274072673026610262702431723864237892313322869225162245722156219772172121633212202075620552202931953019362192511935218838187691871218826185541866418477185151823017994
Percentage of LiabilitiesAndStockholdersEquity25.224.925.125.125.224.724.624.724.424.022.923.823.321.821.521.621.320.820.521.124.427.927.70.00.00.029.00.00.029.929.829.929.529.729.630.430.531.231.232.332.532.7
Percentage of Assets25.224.925.125.125.224.724.624.724.424.022.923.823.321.821.521.621.320.820.521.124.427.927.728.828.629.029.030.029.429.929.829.929.529.729.630.430.531.231.232.332.532.7
Percentage of Assets so:AlabamaPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:GeorgiaPower


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value476254734947080470464582545179445414441543239425384036536861359613719936779371063618835248348353424834015328023286531726317483151631030299152966929189289072920729127289952880328421280782733727151267052646925914
Percentage of LiabilitiesAndStockholdersEquity37.837.838.338.238.338.037.537.837.637.334.533.031.933.333.133.633.332.131.832.237.441.742.00.00.00.043.80.00.045.044.845.145.545.845.645.946.145.745.846.647.247.1
Percentage of Assets37.837.838.338.238.338.037.537.837.637.334.533.031.933.333.133.633.332.131.832.237.441.742.042.242.844.043.844.244.745.044.845.145.545.845.645.946.145.745.846.647.247.1
Percentage of Assets so:GeorgiaPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:MississippiPower


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value541248954912484848214860503549464874478548864817465347124866505555318088823581657987791678407913794769476756631163645827584854725438540554515119461443223671284025722476
Percentage of LiabilitiesAndStockholdersEquity4.33.94.03.94.04.14.24.24.24.24.24.34.14.24.44.65.17.47.57.78.810.110.00.00.00.09.50.00.09.09.18.58.58.58.68.37.67.26.25.04.64.5
Percentage of Assets4.33.94.03.94.04.14.24.24.24.24.24.34.14.24.44.65.17.47.57.78.810.110.010.510.79.79.59.39.69.09.18.58.58.58.68.37.67.26.25.04.64.5
Percentage of Assets so:MississippiPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernCompanyGas


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value23235233772263021932215002161721687210472076120952214482039822112225682298722190218092168321853
Percentage of LiabilitiesAndStockholdersEquity18.518.618.417.818.018.218.317.918.118.418.318.319.620.220.720.120.119.819.9
Percentage of Assets18.518.618.417.818.018.218.317.918.118.418.318.319.620.220.720.120.119.819.9
Percentage of Assets so:SouthernCompanyGas100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

so:SouthernPower


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value137081399513235134241355713646143001439714518151041488315355154281518215206146481470314681151691235111082899989057040622655645549460846054403442944494139385837793781378535963580375735363437
Percentage of LiabilitiesAndStockholdersEquity10.911.210.810.911.311.512.012.212.613.212.713.713.713.613.713.313.513.413.811.612.211.411.40.00.00.07.80.00.06.86.96.96.56.16.06.16.26.06.06.66.36.2
Percentage of Assets10.911.210.810.911.311.512.012.212.613.212.713.713.713.613.713.313.513.413.811.612.211.411.49.48.47.87.86.86.96.86.96.96.56.16.06.16.26.06.06.66.36.2
Percentage of Assets so:SouthernPower100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-03-312013-12-312013-09-302013-06-302012-12-31
Value279722750524723248772363624676241672408223372250942475824547220152079720592199491907019008187781804018297
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets22.823.221.122.321.022.121.821.821.522.922.623.124.226.426.328.129.429.429.028.229.0

us-gaap:StockholdersEquity dei:LegalEntity

so:AlabamaPower


Stockholders
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value98108955747775857401733568296866670766416323640262246199599260005849578957525762560855635502560254665398
Percentage of StockholdersEquity35.132.630.230.531.329.728.328.528.726.525.526.128.329.829.10.00.00.028.80.00.029.228.929.830.329.5
Percentage of Assets8.07.56.46.86.66.66.26.26.26.15.86.06.87.97.78.07.98.18.18.58.48.68.58.78.58.5
Percentage of Assets so:AlabamaPower31.830.728.028.528.230.228.628.929.029.028.128.528.128.227.627.727.627.928.028.428.728.728.628.929.028.8

so:GeorgiaPower


Stockholders
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value1650115065143231385112702134201193112007117131165011356112651093510889107191075510453104061042110027972296359591959993289273
Percentage of StockholdersEquity59.054.857.955.753.754.449.449.950.146.445.945.949.752.452.10.00.00.052.20.00.050.550.551.151.750.7
Percentage of Assets13.412.712.312.411.312.010.710.910.810.610.410.612.013.813.714.314.114.514.714.814.614.914.914.814.614.7
Percentage of Assets so:GeorgiaPower35.033.835.537.635.336.132.432.432.433.132.632.932.133.232.633.932.933.033.633.532.833.033.232.932.032.2

so:MississippiPower


Stockholders
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value17421652160914431398135113581914187329262943262826012373235923032248219720842021217019512176173115481749
Percentage of StockholdersEquity6.26.06.55.85.95.55.67.98.011.711.910.711.811.411.50.00.00.010.40.00.010.211.59.28.69.6
Percentage of Assets1.41.41.41.31.21.21.21.71.72.72.72.52.93.03.03.13.03.12.93.03.33.03.42.72.42.8
Percentage of Assets so:MississippiPower35.532.832.930.030.028.727.937.933.936.235.732.232.630.030.129.128.331.630.832.034.133.537.231.628.532.1

so:SouthernCompanyGas


Stockholders
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302017-12-312016-12-31
Value9767950685708623906190229109
Percentage of StockholdersEquity34.934.634.734.738.337.336.8
Percentage of Assets7.98.07.37.78.08.18.3
Percentage of Assets so:SouthernCompanyGas43.243.840.042.341.039.241.7

so:SouthernPower


Stockholders
Period End2020-12-312019-12-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-12-31
Value23692368296841134518520951384448440744094430340527762466248320611767175317511590155915611563157315191522
Percentage of StockholdersEquity8.58.612.016.519.121.121.318.518.917.617.913.912.611.912.10.00.00.08.80.00.08.28.28.48.48.3
Percentage of Assets1.92.02.53.74.04.74.64.04.14.04.03.23.13.13.22.72.42.42.52.42.32.42.42.42.42.4
Percentage of Assets so:SouthernPower17.916.619.926.829.334.333.830.430.030.029.227.625.027.427.929.328.431.531.634.533.935.535.335.436.740.3

Assets Current

us-gaap:AssetsCurrent

us-gaap:AssetsCurrent


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-312014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value9551946986171057490699430981799178352870995839384116199524100729202883784279722965815149546165266370514055995785600159326162669663736041627264955502524058835873
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 Assets7.67.67.08.67.67.98.38.47.37.68.28.410.38.59.18.38.17.78.99.116.76.98.39.07.98.78.99.49.49.810.810.510.110.611.39.89.510.711.3

us-gaap:AssetsCurrent dei:LegalEntity

so:AlabamaPower


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302010-12-31
Value257123382247285327052610258630862384229719092338229321362006242520792099180521111885192018012206187119231953211915581649169119111629167417572039178719081814206717551822
Percentage of AssetsCurrent26.924.726.127.029.827.726.331.128.526.419.924.919.722.419.926.423.524.918.621.912.435.227.60.00.00.030.70.00.032.130.233.027.128.228.530.528.031.628.931.831.931.0
Percentage of Assets2.01.91.82.32.32.22.22.62.12.01.62.12.01.91.82.21.91.91.62.02.12.42.32.92.5