1.0.0.3 false CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $) In Thousands 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 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 6 Operating Activities: 4 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 No definition available. false 7 Consolidated net income 5 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 1442894000 1442894 false false 2 true true 1604607000 1604607 false false No definition available. No authoritative reference available. false 8 Adjustments to reconcile consolidated net income to net cash provided from operating activities -- 5 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 No definition available. false 9 Depreciation and amortization, total 6 us-gaap_DepreciationAmortizationAndAccretionNet us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1310854000 1310854 false false 2 false true 1265696000 1265696 false false No definition available. No authoritative reference available. false 10 Deferred income taxes and investment tax credits 6 us-gaap_DeferredIncomeTaxesAndTaxCredits us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -14565000 -14565 false false 2 false true 46006000 46006 false false No definition available. No authoritative reference available. false 11 Deferred revenues 6 us-gaap_RecognitionOfDeferredRevenue us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -40781000 -40781 false false 2 false true 94924000 94924 false false No definition available. No authoritative reference available. false 12 Allowance for equity funds used during construction 6 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 -141173000 -141173 false false 2 false true -111612000 -111612 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 13 Equity in income (losses) of unconsolidated subsidiaries 6 us-gaap_IncomeLossFromEquityMethodInvestments us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 330000 330 false false 2 false true -6129000 -6129 false false No definition available. No authoritative reference available. false 14 Leveraged lease income (losses) 6 us-gaap_LeveragedLeasesIncomeStatementNetIncomeFromLeveragedLeases us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -24695000 -24695 false false 2 false true 53611000 53611 false false No definition available. No authoritative reference available. false 15 Gain on disposition of lease termination 6 us-gaap_GainLossOnContractTermination us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -26300000 -26300 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 16 Loss on extinguishment of debt 6 us-gaap_GainsLossesOnExtinguishmentOfDebtBeforeWriteOffOfDeferredDebtIssuanceCost us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 17184000 17184 false false 2 false true 0 0 false false No definition available. No authoritative reference available. false 17 Pension, postretirement, and other employee benefits 6 us-gaap_PensionAndOtherPostretirementBenefitExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 42775000 42775 false false 2 false true 75965000 75965 false false No definition available. No authoritative reference available. false 18 Stock option expense 6 us-gaap_StockOptionPlanExpense us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 20850000 20850 false false 2 false true 17730000 17730 false false No definition available. No authoritative reference available. false 19 Hedge settlements 6 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 -16167000 -16167 false false 2 false true 17289000 17289 false false The cash outflow (inflow) for a financial contract that settles in the period relating to operating activities. No authoritative reference available. false 20 Other, net 6 us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesOther us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 10036000 10036 false false 2 false true -56200000 -56200 false false No definition available. No authoritative reference available. false 21 Changes in certain current assets and liabilities -- 6 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 No definition available. false 22 -Receivables 7 us-gaap_IncreaseDecreaseInReceivables us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 319286000 319286 false false 2 false true -522004000 -522004 false false No definition available. No authoritative reference available. false 23 -Fossil fuel stock 7 us-gaap_IncreaseDecreaseInFossilFuelInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -361520000 -361520 false false 2 false true -112328000 -112328 false false No definition available. No authoritative reference available. false 24 -Materials and supplies 7 us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventories us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -40811000 -40811 false false 2 false true -25347000 -25347 false false No definition available. No authoritative reference available. false 25 -Other current assets 7 us-gaap_IncreaseDecreaseInOtherOperatingAssets us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -50977000 -50977 false false 2 false true -33896000 -33896 false false No definition available. No authoritative reference available. false 26 -Accounts payable 7 us-gaap_IncreaseDecreaseInAccountsPayable us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -210459000 -210459 false false 2 false true -45079000 -45079 false false No definition available. No authoritative reference available. false 27 -Accrued taxes 7 so_IncreaseDecreaseInAccuredTaxes 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 238988000 238988 false false 2 false true 409684000 409684 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 28 -Accrued compensation 7 us-gaap_IncreaseDecreaseInAccruedSalaries us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -273349000 -273349 false false 2 false true -86436000 -86436 false false No definition available. No authoritative reference available. false 29 -Other current liabilities 7 us-gaap_IncreaseDecreaseInOtherOperatingLiabilities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 157384000 157384 false false 2 false true 49651000 49651 false false No definition available. No authoritative reference available. true 30 Net cash provided from operating activities 5 us-gaap_NetCashProvidedByUsedInOperatingActivities us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 2359784000 2359784 false false 2 false true 2636132000 2636132 false false No definition available. No authoritative reference available. true 31 Investing Activities: 4 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 No definition available. false 32 Property additions 5 us-gaap_PaymentsToAcquirePropertyPlantAndEquipment us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -3179009000 -3179009 false false 2 false true -2860118000 -2860118 false false No definition available. No authoritative reference available. false 33 Investment in restricted cash from pollution control revenue bonds 5 us-gaap_PaymentsForInvestmentInRestrictedCashFromPollutionControlBond us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -49528000 -49528 false false 2 false true -5454000 -5454 false false No definition available. No authoritative reference available. false 34 Distribution of restricted cash from pollution control revenue bonds 5 us-gaap_ProceedsFromDistributionOfRestrictedCashFromPollutionControlBond us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 90088000 90088 false false 2 false true 46782000 46782 false false No definition available. No authoritative reference available. false 35 Nuclear decommissioning trust fund purchases 5 us-gaap_PaymentsToInvestInDecommissioningFund us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1066688000 -1066688 false false 2 false true -581171000 -581171 false false No definition available. No authoritative reference available. false 36 Nuclear decommissioning trust fund sales 5 us-gaap_ProceedsFromDecommissioningFund us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 1019401000 1019401 false false 2 false true 574291000 574291 false false No definition available. No authoritative reference available. false 37 Proceeds from property sales 5 us-gaap_ProceedsFromSaleOfProductiveAssets us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 339911000 339911 false false 2 false true 5718000 5718 false false No definition available. No authoritative reference available. false 38 Cost of removal, net of salvage 5 us-gaap_PaymentsForProceedsFromRemovalCosts us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -85022000 -85022 false false 2 false true -74714000 -74714 false false No definition available. No authoritative reference available. false 39 Change in construction payables 5 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 110265000 110265 false false 2 false true -8703000 -8703 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 40 Other investing activities 5 us-gaap_PaymentsForProceedsFromOtherInvestingActivities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -35766000 -35766 false false 2 false true -76402000 -76402 false false No definition available. No authoritative reference available. true 41 Net cash used for investing activities 5 us-gaap_NetCashProvidedByUsedInInvestingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -2856348000 -2856348 false false 2 false true -2979771000 -2979771 false false No definition available. No authoritative reference available. true 42 Financing Activities: 4 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 No definition available. false 43 Increase (decrease) in notes payable, net 5 us-gaap_ProceedsFromRepaymentsOfShortTermDebt us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 118124000 118124 false false 2 false true 62302000 62302 false false No definition available. No authoritative reference available. false 44 Proceeds -- 5 so_Proceeds so false na duration string The abstract for the Proceeds subheading on the Financing Activities section of the Cash Flow Statement. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false The abstract for the Proceeds subheading on the Financing Activities section of the Cash Flow Statement. false 45 Long-term debt issuances 6 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 2216010000 2216010 false false 2 false true 2416035000 2416035 false false No definition available. No authoritative reference available. false 46 Common stock issuances 6 us-gaap_ProceedsFromIssuanceOfCommonStock us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 668529000 668529 false false 2 false true 381200000 381200 false false No definition available. No authoritative reference available. false 47 Redemptions -- 5 so_Redemptions so false na duration string The abstract for the Redemptions subheading on the Financing Activities section of the Cash Flow Statement. false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false The abstract for the Redemptions subheading on the Financing Activities section of the Cash Flow Statement. false 48 Long-term debt 6 us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1229484000 -1229484 false false 2 false true -769789000 -769789 false false No definition available. No authoritative reference available. false 49 Redeemable preferred stock 6 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 -125000 false false No definition available. No authoritative reference available. false 50 Payment of common stock dividends 5 us-gaap_PaymentsOfDividendsCommonStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -1018928000 -1018928 false false 2 false true -954438000 -954438 false false No definition available. No authoritative reference available. false 51 Payments of dividends on preferred and preference stock of subsidiaries 5 us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStock us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -48675000 -48675 false false 2 false true -49497000 -49497 false false No definition available. No authoritative reference available. false 52 Other financing activities 5 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -18732000 -18732 false false 2 false true -11705000 -11705 false false No definition available. No authoritative reference available. true 53 Net cash provided from financing activities 5 us-gaap_NetCashProvidedByUsedInFinancingActivities us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true 686844000 686844 false false 2 false true 949108000 949108 false false No definition available. No authoritative reference available. true 54 Net Change in Cash and Cash Equivalents 4 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false true 190280000 190280 false false 2 false true 605469000 605469 false false No definition available. No authoritative reference available. false 55 Cash and Cash Equivalents at Beginning of Period 3 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false true false false 1 false true 416581000 416581 false false 2 false true 200550000 200550 false false No definition available. No authoritative reference available. false 56 Cash and Cash Equivalents at End of Period 3 us-gaap_CashAndCashEquivalentsAtCarryingValue us-gaap true debit instant monetary No definition available. false false false false false false false true false 1 false true 606861000 606861 false false 2 false true 806019000 806019 false false No definition available. No authoritative reference available. false 58 Cash paid during the period for -- 4 so_CashPaidDuringPeriodFor so false na duration string The abstract for the "Cash paid during the period for --" subheading on the Supplemental Cash Flow Information section of the... false false false false false true false false false 1 false false 0 0 false false 2 false false 0 0 false false The abstract for the "Cash paid during the period for --" subheading on the Supplemental Cash Flow Information section of the Cash Flow Statement. false 59 Interest (net of $59,849 and $54,404 capitalized for 2009 and 2008, respectively) 5 us-gaap_InterestPaidNet us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 589919000 589919 false false 2 false true 575597000 575597 false false No definition available. No authoritative reference available. false 60 Income taxes (net of refunds) 5 us-gaap_IncomeTaxesPaidNet us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 true true 644541000 644541 false false 2 true true 489600000 489600 false false No definition available. No authoritative reference available. false false 2 54 false Thousands UnKnown UnKnown false true