1.0.0.3 false Consolidated Statements of Cash Flows (USD $) In Millions false 1 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 2 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 false 3 $ false false Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 3 Operating Activities: 1 us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 4 Consolidated net income 2 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 1708000000 1708 false false 2 true true 1807000000 1807 false false 3 true true 1782000000 1782 false false No definition available. No authoritative reference available. false 5 Adjustments to reconcile consolidated net income to net cash provided from operating activities - 2 us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 6 Depreciation and amortization, total 3 us-gaap_DepreciationAmortizationAndAccretionNet us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1788000000 1788 false false 2 false true 1704000000 1704 false false 3 false true 1486000000 1486 false false No definition available. No authoritative reference available. false 7 Deferred income taxes 3 us-gaap_DeferredIncomeTaxExpenseBenefit us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 25000000 25 false false 2 false true 215000000 215 false false 3 false true 7000000 7 false false No definition available. No authoritative reference available. false 8 Deferred revenues 3 us-gaap_RecognitionOfDeferredRevenue us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -54000000 -54 false false 2 false true 120000000 120 false false 3 false true -2000000 -2 false false No definition available. No authoritative reference available. false 9 Allowance for equity funds used during construction 3 so_AllowanceForEquityFundsUsedDuringConstruction so false credit duration monetary Total increase in earnings in the period representing the cost of equity (rate of return) used to finance construction of... false false false false false false false false false 1 false true -200000000 -200 false false 2 false true -152000000 -152 false false 3 false true -106000000 -106 false false Total increase in earnings in the period representing the cost of equity (rate of return) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments. No authoritative reference available. false 10 Equity in (income) losses of unconsolidated subsidiaries 3 us-gaap_IncomeLossFromEquityMethodInvestments us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 1000000 1 false false 2 false true -11000000 -11 false false 3 false true 24000000 24 false false No definition available. No authoritative reference available. false 11 Leveraged lease (income) losses 3 us-gaap_LeveragedLeasesIncomeStatementNetIncomeFromLeveragedLeases us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -31000000 -31 false false 2 false true 85000000 85 false false 3 false true -40000000 -40 false false No definition available. No authoritative reference available. false 12 Gain on disposition of lease termination 3 us-gaap_GainLossOnContractTermination us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -26000000 -26 false false 2 false true 0 0 false false 3 false true 0 0 false false No definition available. No authoritative reference available. false 13 Loss on extinguishment of debt 3 us-gaap_GainsLossesOnExtinguishmentOfDebtBeforeWriteOffOfDeferredDebtIssuanceCost us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 17000000 17 false false 2 false true 0 0 false false 3 false true 0 0 false false No definition available. No authoritative reference available. false 14 Pension, postretirement, and other employee benefits 3 us-gaap_PensionAndOtherPostretirementBenefitExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -3000000 -3 false false 2 false true 21000000 21 false false 3 false true 39000000 39 false false No definition available. No authoritative reference available. false 15 Stock based compensation expense 3 us-gaap_StockOptionPlanExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 23000000 23 false false 2 false true 20000000 20 false false 3 false true 28000000 28 false false No definition available. No authoritative reference available. false 16 Hedge settlements 3 so_HedgeSettlements so false credit duration monetary The cash outflow (inflow) for a financial contract that settles in the period relating to operating activities. false false false false false false false false false 1 false true -19000000 -19 false false 2 false true 15000000 15 false false 3 false true 10000000 10 false false The cash outflow (inflow) for a financial contract that settles in the period relating to operating activities. No authoritative reference available. false 17 Other, net 3 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesOther us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 79000000 79 false false 2 false true -97000000 -97 false false 3 false true 80000000 80 false false No definition available. No authoritative reference available. false 18 Changes in certain current assets and liabilities - 3 us-gaap_IncreaseDecreaseInOperatingCapitalAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 19 -Receivables 4 us-gaap_IncreaseDecreaseInReceivables us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 585000000 585 false false 2 false true -176000000 -176 false false 3 false true 165000000 165 false false No definition available. No authoritative reference available. false 20 -Fossil fuel stock 4 us-gaap_IncreaseDecreaseInFossilFuelInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -432000000 -432 false false 2 false true -303000000 -303 false false 3 false true -39000000 -39 false false No definition available. No authoritative reference available. false 21 -Materials and supplies 4 us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -39000000 -39 false false 2 false true -23000000 -23 false false 3 false true -71000000 -71 false false No definition available. No authoritative reference available. false 22 -Other current assets 4 us-gaap_IncreaseDecreaseInOtherOperatingAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -47000000 -47 false false 2 false true -36000000 -36 false false 3 false true 0 0 false false No definition available. No authoritative reference available. false 23 -Accounts payable 4 us-gaap_IncreaseDecreaseInAccountsPayable us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -125000000 -125 false false 2 false true -74000000 -74 false false 3 false true 105000000 105 false false No definition available. No authoritative reference available. false 24 -Accrued taxes 4 so_IncreaseDecreaseInAccruedTaxes so false debit duration monetary The net change during the period in the amount of cash payments due to taxing authorities for income and nonincome-related... false false false false false false false false false 1 false true -95000000 -95 false false 2 false true 293000000 293 false false 3 false true -19000000 -19 false false The net change during the period in the amount of cash payments due to taxing authorities for income and nonincome-related taxes. No authoritative reference available. false 25 -Accrued compensation 4 us-gaap_IncreaseDecreaseInAccruedSalaries us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -226000000 -226 false false 2 false true 36000000 36 false false 3 false true -40000000 -40 false false No definition available. No authoritative reference available. false 26 -Other current liabilities 4 us-gaap_IncreaseDecreaseInOtherOperatingLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 334000000 334 false false 2 false true 20000000 20 false false 3 false true 25000000 25 false false No definition available. No authoritative reference available. true 27 Net cash provided from operating activities 3 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 3263000000 3263 false false 2 false true 3464000000 3464 false false 3 false true 3434000000 3434 false false No definition available. No authoritative reference available. true 28 Investing Activities: 1 us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 29 Property additions 2 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -4670000000 -4670 false false 2 false true -3961000000 -3961 false false 3 false true -3546000000 -3546 false false No definition available. No authoritative reference available. false 30 Investment in restricted cash from pollution control revenue bonds 2 us-gaap_PaymentsForInvestmentInRestrictedCashFromPollutionControlBond us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -55000000 -55 false false 2 false true -96000000 -96 false false 3 false true -157000000 -157 false false No definition available. No authoritative reference available. false 31 Distribution of restricted cash from pollution control revenue bonds 2 us-gaap_ProceedsFromDistributionOfRestrictedCashFromPollutionControlBond us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 119000000 119 false false 2 false true 69000000 69 false false 3 false true 78000000 78 false false No definition available. No authoritative reference available. false 32 Nuclear decommissioning trust fund purchases 2 us-gaap_PaymentsToInvestInDecommissioningFund us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1234000000 -1234 false false 2 false true -720000000 -720 false false 3 false true -783000000 -783 false false No definition available. No authoritative reference available. false 33 Nuclear decommissioning trust fund sales 2 us-gaap_ProceedsFromDecommissioningFund us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1228000000 1228 false false 2 false true 712000000 712 false false 3 false true 775000000 775 false false No definition available. No authoritative reference available. false 34 Proceeds from property sales 2 us-gaap_ProceedsFromSaleOfProductiveAssets us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 340000000 340 false false 2 false true 34000000 34 false false 3 false true 33000000 33 false false No definition available. No authoritative reference available. false 35 Cost of removal, net of salvage 2 us-gaap_PaymentsForProceedsFromRemovalCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -119000000 -119 false false 2 false true -123000000 -123 false false 3 false true -108000000 -108 false false No definition available. No authoritative reference available. false 36 Change in construction payables 2 so_ChangeInConstructionPayables so false debit duration monetary The net change during the reporting period in the aggregate amount of construction obligations due within one year (or one... false false false false false false false false false 1 false true 215000000 215 false false 2 false true 83000000 83 false false 3 false true 38000000 38 false false The net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities. No authoritative reference available. false 37 Other investing activities 2 us-gaap_PaymentsForProceedsFromOtherInvestingActivities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -143000000 -143 false false 2 false true -124000000 -124 false false 3 false true -39000000 -39 false false No definition available. No authoritative reference available. true 38 Net cash used for investing activities 2 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -4319000000 -4319 false false 2 false true -4126000000 -4126 false false 3 false true -3709000000 -3709 false false No definition available. No authoritative reference available. true 39 Financing Activities: 1 us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false No definition available. false 40 Decrease in notes payable, net 2 us-gaap_ProceedsFromRepaymentsOfShortTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -306000000 -306 false false 2 false true -314000000 -314 false false 3 false true -669000000 -669 false false No definition available. No authoritative reference available. false 41 Proceeds - 2 so_ProceedsAbstract so false na duration string Proceeds. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false Proceeds. false 42 Long-term debt issuances 3 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 3042000000 3042 false false 2 false true 3687000000 3687 false false 3 false true 3826000000 3826 false false No definition available. No authoritative reference available. false 43 Preferred and preference stock 3 us-gaap_ProceedsFromMinorityShareholders us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true 0 0 false false 3 false true 470000000 470 false false No definition available. No authoritative reference available. false 44 Common stock issuances 3 us-gaap_ProceedsFromIssuanceOfCommonStock us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1286000000 1286 false false 2 false true 474000000 474 false false 3 false true 538000000 538 false false No definition available. No authoritative reference available. false 45 Redemptions - 2 so_RedemptionsAbstract so false na duration string Redemptions. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false 3 false false 0 0 false false Redemptions. false 46 Long-term debt 3 us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1234000000 -1234 false false 2 false true -1469000000 -1469 false false 3 false true -2565000000 -2565 false false No definition available. No authoritative reference available. false 47 Redeemable preferred stock 3 us-gaap_PaymentsForRepurchaseOfRedeemablePreferredStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 0 0 false false 2 false true -125000000 -125 false false 3 false true 0 0 false false No definition available. No authoritative reference available. false 48 Payment of common stock dividends 2 us-gaap_PaymentsOfDividendsCommonStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1369000000 -1369 false false 2 false true -1280000000 -1280 false false 3 false true -1205000000 -1205 false false No definition available. No authoritative reference available. false 49 Payment of dividends on preferred and preference stock of subsidiaries 2 us-gaap_PaymentsOfDividendsMinorityInterest us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -65000000 -65 false false 2 false true -66000000 -66 false false 3 false true -40000000 -40 false false No definition available. No authoritative reference available. false 50 Other financing activities 2 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -25000000 -25 false false 2 false true -29000000 -29 false false 3 false true -46000000 -46 false false No definition available. No authoritative reference available. true 51 Net cash provided from financing activities 2 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1329000000 1329 false false 2 false true 878000000 878 false false 3 false true 309000000 309 false false No definition available. No authoritative reference available. true 52 Net Change in Cash and Cash Equivalents 1 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 273000000 273 false false 2 false true 216000000 216 false false 3 false true 34000000 34 false false No definition available. No authoritative reference available. false 53 Cash and Cash Equivalents at Beginning of Year 1 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false true false false 1 false true 417000000 417 false false 2 false true 201000000 201 false false 3 false true 167000000 167 false false No definition available. No authoritative reference available. false 54 Cash and Cash Equivalents at End of Year 1 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false true false 1 true true 690000000 690 false false 2 true true 417000000 417 false false 3 true true 201000000 201 false false No definition available. No authoritative reference available. false false 3 52 false Millions UnKnown UnKnown false true