2.2.0.25falsefalse0120 - Statement - Consolidated Statements of Cash FlowstruefalseIn Millionsfalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) USD ($) / shares $Jan-01-2010_Dec-31-2010http://www.sec.gov/CIK0000092122duration2010-01-01T00:00:002010-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDEPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalseUSDfalsefalse1/1/2009 - 12/31/2009 USD ($) USD ($) / shares $TwelveMonthsEnded_31Dec2009http://www.sec.gov/CIK0000092122duration2009-01-01T00:00:002009-12-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDEPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDUSD$3falsefalseUSDfalsefalse1/1/2008 - 12/31/2008 USD ($) USD ($) / shares $TwelveMonthsEnded_31Dec2008http://www.sec.gov/CIK0000092122duration2008-01-01T00:00:002008-12-31T00:00:00PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDEPSDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$3true0us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThe net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities include all transactions and events that are not defined as investing or financing activities. Operating activities generally involve producing and delivering goods and providing services. Cash flows from operating activities are generally the cash effects of transactions and other events that enter into the determination of net income.falsefalseOperating Activities:4false0us-gaap_ProfitLossus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse20400000002040falsetruefalsefalsefalse2truefalsefalse17080000001708falsetruefalsefalsefalse3truefalsefalse18070000001807falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) falsefalseConsolidated net income5true0us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseAdjustments to reconcile consolidated net income to net cash provided from operating activities --6false0us-gaap_DepreciationAmortizationAndAccretionNetus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse18310000001831falsefalsefalsefalsefalse2truefalsefalse17880000001788falsefalsefalsefalsefalse3truefalsefalse17040000001704falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by (used in) operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalseDepreciation and amortization, total7false0us-gaap_DeferredIncomeTaxExpenseBenefitus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse10380000001038falsefalsefalsefalsefalse2truefalsefalse2500000025falsefalsefalsefalsefalse3truefalsefalse215000000215falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe component of income tax expense for the period representing the net change in the entity's deferred tax assets and liabilities pertaining to continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 289 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 falsefalseDeferred income taxes8false0us-gaap_RecognitionOfDeferredRevenueus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-103000000-103falsefalsefalsefalsefalse2truefalsefalse-54000000-54falsefalsefalsefalsefalse3truefalsefalse120000000120falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. For cash flows, this element primarily pertains to amortization of deferred credits on long-term arrangements. As a noncash item, it is deducted from net income when calculating cash provided by (used in) operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A -Subsection 1 falsefalseDeferred revenues9false0us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-194000000-194falsefalsefalsefalsefalse2truefalsefalse-200000000-200falsefalsefalsefalsefalse3truefalsefalse-152000000-152falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 71 -Paragraph 15 falsefalseAllowance for equity funds used during construction10false0us-gaap_LeveragedLeasesIncomeStatementNetIncomeFromLeveragedLeasesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-18000000-18falsefalsefalsefalsefalse2truefalsefalse-31000000-31falsefalsefalsefalsefalse3truefalsefalse8500000085falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe total recognized during the period for income on leases meeting the criteria for classification as leveraged leases.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 13 -Paragraph 47 falsefalseLeveraged lease (income) losses11false0us-gaap_GainLossOnContractTerminationus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse-26000000-26falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis element represents the income received from or payment made to a third party in connection with the termination of a contract between the parties. The termination may be due to many causes including early termination of a lease by a lessee, a breach of contract by one or the other party, a failure to perform.No authoritative reference available.falsefalseGain on disposition of lease termination12false0us-gaap_GainsLossesOnExtinguishmentOfDebtBeforeWriteOffOfDeferredDebtIssuanceCostus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse1700000017falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryReflects the difference between the fair value of payments made to legally extinguish a debt and its carrying value at that time. This item excludes the write-off of amounts previously capitalized as debt issuance costs.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 26 -Paragraph 20, 21 falsefalseLoss on extinguishment of debt13false0us-gaap_PensionAndOtherPostretirementBenefitExpenseus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-614000000-614falsefalsefalsefalsefalse2truefalsefalse-3000000-3falsefalsefalsefalsefalse3truefalsefalse2100000021falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss on assets, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period shall be the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost shall be accrued during the employee's service period).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph h Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5, 11 falsefalsePension, postretirement, and other employee benefits14false0us-gaap_StockOptionPlanExpenseus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse3300000033falsefalsefalsefalsefalse2truefalsefalse2300000023falsefalsefalsefalsefalse3truefalsefalse2000000020falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe noncash expense that accounts for the value of stock options distributed to employees as compensation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph i falsefalseStock based compensation expense15false0so_HedgeSettlementssofalsecreditdurationThe cash outflow (inflow) for a financial contract that settles in the period relating to operating activities.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse20000002falsefalsefalsefalsefalse2truefalsefalse-19000000-19falsefalsefalsefalsefalse3truefalsefalse1500000015falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow (inflow) for a financial contract that settles in the period relating to operating activities.No authoritative reference available.falsefalseHedge settlements16false0so_CertainRegulatoryAssetssofalsecreditdurationThe net change during the reporting period in the value of certain assets that are created when regulatory agencies permits...falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-51000000-51falsefalsefalsefalsefalse2truefalsefalse-22000000-22falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in the value of certain assets that are created when regulatory agencies permits public utilities to defer costs to the balance sheet.No authoritative reference available.falsefalseGeneration construction screening costs17false0us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesOtherus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse8600000086falsefalsefalsefalsefalse2truefalsefalse102000000102falsefalsefalsefalsefalse3truefalsefalse-108000000-108falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTransactions that do not result in cash inflows or outflows in the period in which they occur, but affect net income and thus are removed when calculating net cash flow from operating activities using the indirect cash flow method. This element is used when there is not a more specific and appropriate element.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalseOther, net18true0us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseChanges in certain current assets and liabilities --19false0us-gaap_IncreaseDecreaseInReceivablesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse8000000080falsefalsefalsefalsefalse2truefalsefalse585000000585falsefalsefalsefalsefalse3truefalsefalse-176000000-176falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalse-Receivables20false0us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse135000000135falsefalsefalsefalsefalse2truefalsefalse-432000000-432falsefalsefalsefalsefalse3truefalsefalse-303000000-303falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalse-Fossil fuel stock21false0us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventoriesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-30000000-30falsefalsefalsefalsefalse2truefalsefalse-39000000-39falsefalsefalsefalsefalse3truefalsefalse-23000000-23falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalse-Materials and supplies22false0us-gaap_IncreaseDecreaseInOtherOperatingAssetsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-17000000-17falsefalsefalsefalsefalse2truefalsefalse-47000000-47falsefalsefalsefalsefalse3truefalsefalse-36000000-36falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in other operating assets not otherwise defined in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalse-Other current assets23false0us-gaap_IncreaseDecreaseInAccountsPayableus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse40000004falsefalsefalsefalsefalse2truefalsefalse-125000000-125falsefalsefalsefalsefalse3truefalsefalse-74000000-74falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of obligations due within one year (or one business cycle). This may include trade payables, amounts due to related parties, royalties payable, and other obligations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalse-Accounts payable24false0so_IncreaseDecreaseInAccruedTaxessofalsedebitdurationThe net change during the period in the amount of cash payments due to taxing authorities for income and nonincome-related...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-308000000-308falsefalsefalsefalsefalse2truefalsefalse-95000000-95falsefalsefalsefalsefalse3truefalsefalse293000000293falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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.falsefalse-Accrued taxes25false0us-gaap_IncreaseDecreaseInAccruedSalariesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse180000000180falsefalsefalsefalsefalse2truefalsefalse-226000000-226falsefalsefalsefalsefalse3truefalsefalse3600000036falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryNet change during the period in the amount of salaries accrued at the period end.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 falsefalse-Accrued compensation26false0us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse-103000000-103falsefalsefalsefalsefalse2truefalsefalse334000000334falsefalsefalsefalsefalse3truefalsefalse2000000020falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change during the reporting period in other operating obligations not otherwise defined in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 truefalse-Other current liabilities27false0us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse39910000003991falsefalsefalsefalsefalse2truefalsefalse32630000003263falsefalsefalsefalsefalse3truefalsefalse34640000003464falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash from (used in) all of the entity's operating activities, including those of discontinued operations, of the reporting entity. Operating activities generally involve producing and delivering goods and providing services. Operating activity cash flows include transactions, adjustments, and changes in value that are not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 truefalseNet cash provided from operating activities28true0us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseInvesting Activities:29false0us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-4086000000-4086falsefalsefalsefalsefalse2truefalsefalse-4670000000-4670falsefalsefalsefalsefalse3truefalsefalse-3961000000-3961falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 17 -Subparagraph c falsefalseProperty additions30false0so_PaymentsForInvestmentInRestrictedCashFromRevenueBondsofalsecreditdurationPayments For Investment In Restricted Cash From Revenue Bond.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-50000000-50falsefalsefalsefalsefalse2truefalsefalse-55000000-55falsefalsefalsefalsefalse3truefalsefalse-96000000-96falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryPayments For Investment In Restricted Cash From Revenue Bond.No authoritative reference available.falsefalseInvestment in restricted cash from revenue bonds31false0so_ProceedsFromDistributionOfRestrictedCashFromRevenueBondsofalsedebitdurationProceeds From Distribution Of Restricted Cash From Revenue Bond.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse2500000025falsefalsefalsefalsefalse2truefalsefalse119000000119falsefalsefalsefalsefalse3truefalsefalse6900000069falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryProceeds From Distribution Of Restricted Cash From Revenue Bond.No authoritative reference available.falsefalseDistribution of restricted cash from revenue bonds32false0us-gaap_PaymentsToInvestInDecommissioningFundus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-2009000000-2009falsefalsefalsefalsefalse2truefalsefalse-1234000000-1234falsefalsefalsefalsefalse3truefalsefalse-720000000-720falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow from the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments, government appropriations, and so forth.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15, 17 falsefalseNuclear decommissioning trust fund purchases33false0us-gaap_ProceedsFromDecommissioningFundus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse20040000002004falsefalsefalsefalsefalse2truefalsefalse12280000001228falsefalsefalsefalsefalse3truefalsefalse712000000712falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash inflow from the costs of decontaminating and decommissioning of facilities through collection of revenues derived from utility assessments, government appropriations, and so forth.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15, 16 falsefalseNuclear decommissioning trust fund sales34false0us-gaap_ProceedsFromSaleOfProductiveAssetsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1800000018falsefalsefalsefalsefalse2truefalsefalse340000000340falsefalsefalsefalsefalse3truefalsefalse3400000034falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 16 -Subparagraph c falsefalseProceeds from property sales35false0us-gaap_PaymentsForProceedsFromRemovalCostsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-125000000-125falsefalsefalsefalsefalse2truefalsefalse-119000000-119falsefalsefalsefalsefalse3truefalsefalse-123000000-123falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash inflow (outflow) from the costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, and so forth during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15, 16, 17 falsefalseCost of removal, net of salvage36false0so_ChangeInConstructionPayablessofalsedebitdurationThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-51000000-51falsefalsefalsefalsefalse2truefalsefalse215000000215falsefalsefalsefalsefalse3truefalsefalse8300000083falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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.falsefalseChange in construction payables37false0us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegatedtotal1truefalsefalse1800000018falsefalsefalsefalsefalse2truefalsefalse-143000000-143falsefalsefalsefalsefalse3truefalsefalse-124000000-124falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash outflow (inflow) from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 truefalseOther investing activities38false0us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse-4256000000-4256falsefalsefalsefalsefalse2truefalsefalse-4319000000-4319falsefalsefalsefalsefalse3truefalsefalse-4126000000-4126falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash inflow (outflow) from investing activity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 truefalseNet cash used for investing activities39true0us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseFinancing Activities:40false0us-gaap_ProceedsFromRepaymentsOfShortTermDebtus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse659000000659falsefalsefalsefalsefalse2truefalsefalse-306000000-306falsefalsefalsefalsefalse3truefalsefalse-314000000-314falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash inflow (outflow) for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 falsefalseIncrease (decrease) in notes payable, net41true0so_ProceedsAbstractsofalsenadurationProceeds.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringProceeds.falsefalseProceeds --42false0us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNetus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse31510000003151falsefalsefalsefalsefalse2truefalsefalse30420000003042falsefalsefalsefalsefalse3truefalsefalse36870000003687falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash inflow associated with security instrument that either represents a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph a falsefalseLong-term debt issuances43false0us-gaap_ProceedsFromIssuanceOfCommonStockus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse772000000772falsefalsefalsefalsefalse2truefalsefalse12860000001286falsefalsefalsefalsefalse3truefalsefalse474000000474falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash inflow from the additional capital contribution to the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph a falsefalseCommon stock issuances44true0so_RedemptionsAbstractsofalsenadurationRedemptions.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRedemptions.falsefalseRedemptions --45false0us-gaap_RepaymentsOfLongTermDebtAndCapitalSecuritiesus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-2966000000-2966falsefalsefalsefalsefalse2truefalsefalse-1234000000-1234falsefalsefalsefalsefalse3truefalsefalse-1469000000-1469falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow associated with security instrument that either represents a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. The nature of such security interests included herein may consist of debt securities, long-term capital lease obligations, and capital securities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph b falsefalseLong-term debt46false0us-gaap_PaymentsForRepurchaseOfRedeemablePreferredStockus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1falsefalsefalse00  falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3truefalsefalse-125000000-125falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow for reacquisition of callable preferred stock.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph a falsefalseRedeemable preferred stock47false0us-gaap_PaymentsOfDividendsCommonStockus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-1496000000-1496falsefalsefalsefalsefalse2truefalsefalse-1369000000-1369falsefalsefalsefalsefalse3truefalsefalse-1280000000-1280falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow from the distribution of an entity's earnings in the form of dividends to common shareholders.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph a falsefalsePayment of common stock dividends48false0us-gaap_PaymentsOfDividendsMinorityInterestus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-65000000-65falsefalsefalsefalsefalse2truefalsefalse-65000000-65falsefalsefalsefalsefalse3truefalsefalse-66000000-66falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe cash outflow for the return on capital for noncontrolled interest in the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph a falsefalsePayment of dividends on preferred and preference stock of subsidiaries49false0us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse-33000000-33falsefalsefalsefalsefalse2truefalsefalse-25000000-25falsefalsefalsefalsefalse3truefalsefalse-29000000-29falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash inflow (outflow) from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18, 19, 20 truefalseOther financing activities50false0us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse2200000022falsefalsefalsefalsefalse2truefalsefalse13290000001329falsefalsefalsefalsefalse3truefalsefalse878000000878falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net cash inflow (outflow) from financing activity for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 truefalseNet cash provided from financing activities51false0us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-243000000-243falsefalsefalsefalsefalse2truefalsefalse273000000273falsefalsefalsefalsefalse3truefalsefalse216000000216falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net change between the beginning and ending balance of cash and cash equivalents.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 26 falsefalseNet Change in Cash and Cash Equivalents52false0us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsetruefalsefalseperiodstartlabel1truefalsefalse690000000690falsefalsefalsefalsefalse2truefalsefalse417000000417falsefalsefalsefalsefalse3truefalsefalse201000000201falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryIncludes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 falsefalseCash and Cash Equivalents at Beginning of Year53false0us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaaptruedebitinstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsetruefalseperiodendlabel1truefalsefalse447000000447falsetruefalsefalsefalse2truefalsefalse690000000690falsetruefalsefalsefalse3truefalsefalse417000000417falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryIncludes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Entity may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits should not be reported as cash and cash equivalents.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 26 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 8, 9 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7 -Footnote 1 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 falsefalseCash and Cash Equivalents at End of Year351Consolidated Statements of Cash Flows (USD $)MillionsUnKnownUnKnownUnKnownfalsetrue