2.4.0.81003000 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)truefalsefalse1false USDfalsefalse$D2013Q2YTDhttp://www.sec.gov/CIK0000092122duration2013-01-01T00:00:002013-06-30T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$D2012Q2YTDhttp://www.sec.gov/CIK0000092122duration2012-01-01T00:00:002012-06-30T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 4us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Activities:2false 5us-gaap_ProfitLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse410000000410000000USD$falsetruefalse2truefalsefalse10230000001023000000USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 false2Consolidated net income3true 5us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Adjustments to reconcile consolidated net income to net cash provided from operating activities --4false 6us-gaap_DepreciationAmortizationAndAccretionNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse11400000001140000000USD$falsefalsefalse2truefalsefalse10640000001064000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Depreciation and amortization, total5false 6us-gaap_DeferredIncomeTaxExpenseBenefitus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-141000000-141000000USD$falsefalsefalse2truefalsefalse327000000327000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Deferred Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6510177 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 false2Deferred income taxes6false 6us-gaap_InvestmentTaxCreditus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse8300000083000000USD$falsefalsefalse2truefalsefalse1600000016000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; includes deferred investment tax credits.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Investment tax credits7false 6us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-86000000-86000000USD$falsefalsefalse2truefalsefalse-63000000-63000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 false2Allowance for equity funds used during construction8false 6us-gaap_LeveragedLeasesIncomeStatementNetIncomeFromLeveragedLeasesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse1600000016000000USD$falsefalsefalse2truefalsefalse-11000000-11000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe total recognized during the period for income on leases meeting the criteria for classification as leveraged leases.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=7662751&loc=d3e45152-112736 false2Leveraged lease income (loss)9false 6us-gaap_PensionAndOtherPostretirementBenefitExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse4100000041000000USD$falsefalsefalse2truefalsefalse1300000013000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 false2Pension, postretirement, and other employee benefits10false 6us-gaap_StockOptionPlanExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse3700000037000000USD$falsefalsefalse2truefalsefalse3500000035000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Stock based compensation expense11false 6so_RetailFuelCostOverRecoveryLongTermso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-123000000-123000000USD$falsefalsefalse2truefalsefalse4400000044000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRetail fuel cost over recovery long term.No definition available.false2Retail fuel cost over recovery - long-term12false 6so_EstimatedLossOnIntegratedCoalGasificationCombinedCycleProjectso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse990000000990000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEstimated Loss On Integrated Coal Gasification Combined Cycle ProjectNo definition available.false2Estimated loss on Kemper IGCC13false 6us-gaap_OtherNoncashIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse3100000031000000USD$falsefalsefalse2truefalsefalse-22000000-22000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Other, net14true 6us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Changes in certain current assets and liabilities --15false 7us-gaap_IncreaseDecreaseInReceivablesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-325000000-325000000USD$falsefalsefalse2truefalsefalse-55000000-55000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Receivables16false 7us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse185000000185000000USD$falsefalsefalse2truefalsefalse-305000000-305000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Fossil fuel stock17false 7us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse5200000052000000USD$falsefalsefalse2truefalsefalse-17000000-17000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Materials and supplies18false 7us-gaap_IncreaseDecreaseInOtherOperatingAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-55000000-55000000USD$falsefalsefalse2truefalsefalse-36000000-36000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other assets used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current assets, other noncurrent assets, or a combination of other current and noncurrent assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current assets19false 7us-gaap_IncreaseDecreaseInAccountsPayableus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-52000000-52000000USD$falsefalsefalse2truefalsefalse-167000000-167000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accounts payable20false 7so_IncreaseDecreaseInAccruedTaxesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse60000006000000USD$falsefalsefalse2truefalsefalse4500000045000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes.No definition available.false2-Accrued taxes21false 7us-gaap_IncreaseDecreaseInAccruedSalariesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-257000000-257000000USD$falsefalsefalse2truefalsefalse-216000000-216000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the period in accrued salaries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued compensation22false 7so_IncreaseDecreaseRetailFuelCostOverRecoveryShortTermso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-22000000-22000000USD$falsefalsefalse2truefalsefalse101000000101000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncrease decrease retail fuel cost over recovery short-term.No definition available.false2-Retail fuel cost over recovery - short-term23false 7us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1700000017000000USD$falsefalsefalse2truefalsefalse-19000000-19000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other liabilities used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current liabilities, other noncurrent liabilities, or a combination of other current and noncurrent liabilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current liabilities24false 6us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse19470000001947000000USD$falsefalsefalse2truefalsefalse17570000001757000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 true2Net cash provided from operating activities25true 4us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Investing Activities:26false 5us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-2597000000-2597000000USD$falsefalsefalse2truefalsefalse-2356000000-2356000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Property additions27false 5so_PaymentsForInvestmentInRestrictedCashso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-98000000-98000000USD$falsefalsefalse2truefalsefalse-230000000-230000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryPayments for investment in restricted cash.No definition available.false2Investment of restricted cash28false 5so_ProceedsFromDistributionOfRestrictedCashso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2300000023000000USD$falsefalsefalse2truefalsefalse4900000049000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryProceeds From Distribution Of Restricted CashNo definition available.false2Distribution of restricted cash29false 5us-gaap_PaymentsToInvestInDecommissioningFundus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-548000000-548000000USD$falsefalsefalse2truefalsefalse-576000000-576000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for the purchase of investments that will be held in a decommissioning trust fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Nuclear decommissioning trust fund purchases30false 5us-gaap_ProceedsFromDecommissioningFundus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse546000000546000000USD$falsefalsefalse2truefalsefalse574000000574000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from the sale of assets held in a decommissioning trust fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 false2Nuclear decommissioning trust fund sales31false 5us-gaap_PaymentsForProceedsFromRemovalCostsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-56000000-56000000USD$falsefalsefalse2truefalsefalse-58000000-58000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from the costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, and so forth during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 false2Cost of removal, net of salvage32false 5so_ChangeInConstructionPayablesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse114000000114000000USD$falsefalsefalse2truefalsefalse-115000000-115000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities.No definition available.false2Change in construction payables33false 5us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-13000000-13000000USD$falsefalsefalse2truefalsefalse-79000000-79000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other investing activities34false 5us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-2629000000-2629000000USD$falsefalsefalse2truefalsefalse-2791000000-2791000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash used for investing activities35true 4us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financing Activities:36false 5us-gaap_ProceedsFromRepaymentsOfShortTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse767000000767000000USD$falsefalsefalse2truefalsefalse-406000000-406000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Increase (decrease) in notes payable, net37true 5so_ProceedsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Proceeds --38false 6us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse11970000001197000000USD$falsefalsefalse2truefalsefalse24870000002487000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow associated with security instrument that either represents a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes proceeds from (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Long-term debt issuances39false 6so_InterestBearingRefundableDepositRelatedToAssetSaleso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse150000000150000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInterest bearing refundable deposit related to asset sale.No definition available.false2Interest-bearing refundable deposit related to asset sale40false 6us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStockus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5000000050000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryProceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Preference stock41false 6us-gaap_ProceedsFromIssuanceOfCommonStockus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse161000000161000000USD$falsefalsefalse2truefalsefalse316000000316000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from the additional capital contribution to the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Common stock issuances42true 5so_RedemptionsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Redemptions --43false 6us-gaap_RepaymentsOfLongTermDebtAndCapitalSecuritiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-792000000-792000000USD$falsefalsefalse2truefalsefalse-1319000000-1319000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with security instruments that either represent a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes repayments of (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Long-term debt44false 5us-gaap_PaymentsForRepurchaseOfCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-18000000-18000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow to reacquire common stock during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Common stock repurchased45false 5us-gaap_PaymentsOfDividendsCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-870000000-870000000USD$falsefalsefalse2truefalsefalse-837000000-837000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of common stock dividends46false 5us-gaap_PaymentsOfDividendsMinorityInterestus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-32000000-32000000USD$falsefalsefalse2truefalsefalse-32000000-32000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends provided by the non-wholly owned subsidiary to noncontrolling interests.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of dividends on preferred and preference stock of subsidiaries47false 5us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1500000015000000USD$falsefalsefalse2truefalsefalse1900000019000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other financing activities48false 5us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse478000000478000000USD$falsefalsefalse2truefalsefalse378000000378000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash provided from (used for) financing activities49false 4us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-204000000-204000000USD$falsefalsefalse2truefalsefalse-656000000-656000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 true2Net Change in Cash and Cash Equivalents50false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse628000000628000000USD$falsefalsefalse2truefalsefalse13150000001315000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at Beginning of Period51false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsetruefalseperiodEndLabel1truefalsefalse424000000424000000USD$falsefalsefalse2truefalsefalse659000000659000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at End of Period52true 5so_CashPaidReceivedDuringPeriodAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cash paid (received) during the period for --53false 6us-gaap_InterestPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse384000000384000000USD$falsefalsefalse2truefalsefalse391000000391000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid for interest during the period net of cash paid for interest that is capitalized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Interest (net of capitalized amounts)54false 6us-gaap_IncomeTaxesPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse142000000142000000USD$falsefalsefalse2truefalsefalse-34000000-34000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Income taxes, net55false 4us-gaap_CapitalExpendituresIncurredButNotYetPaidus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse637000000637000000USD$falsefalsefalse2truefalsefalse488000000488000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFuture cash outflow to pay for purchases of fixed assets that have occurred.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 false2Noncash transactions - accrued property additions at end of period56false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse5false USDtruefalse$D2013Q2_dei_LegalEntityAxis_so_AlabamaPowerMemberhttp://www.sec.gov/CIK0000092122duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseAlabama Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_AlabamaPowerMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Alabama Power [Member]57true 4us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Activities:58false 5us-gaap_ProfitLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse334000000334000000USD$falsefalsefalse2truefalsefalse331000000331000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 false2Consolidated net income59true 5us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Adjustments to reconcile consolidated net income to net cash provided from operating activities --60false 6us-gaap_DepreciationAmortizationAndAccretionNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse403000000403000000USD$falsefalsefalse2truefalsefalse380000000380000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Depreciation and amortization, total61false 6us-gaap_DeferredIncomeTaxExpenseBenefitus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5300000053000000USD$falsefalsefalse2truefalsefalse8500000085000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Deferred Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6510177 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 false2Deferred income taxes62false 6us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-16000000-16000000USD$falsefalsefalse2truefalsefalse-9000000-9000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 false2Allowance for equity funds used during construction63false 6us-gaap_StockOptionPlanExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse60000006000000USD$falsefalsefalse2truefalsefalse60000006000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Stock based compensation expense64false 6us-gaap_OtherNoncashIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-18000000-18000000USD$falsefalsefalse2truefalsefalse-33000000-33000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Other, net65true 6us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Changes in certain current assets and liabilities --66false 7us-gaap_IncreaseDecreaseInReceivablesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-65000000-65000000USD$falsefalsefalse2truefalsefalse-46000000-46000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Receivables67false 7us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse7600000076000000USD$falsefalsefalse2truefalsefalse-125000000-125000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Fossil fuel stock68false 7us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse2200000022000000USD$falsefalsefalse2truefalsefalse-6000000-6000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Materials and supplies69false 7us-gaap_IncreaseDecreaseInOtherOperatingAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-45000000-45000000USD$falsefalsefalse2truefalsefalse-31000000-31000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other assets used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current assets, other noncurrent assets, or a combination of other current and noncurrent assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current assets70false 7us-gaap_IncreaseDecreaseInAccountsPayableus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-93000000-93000000USD$falsefalsefalse2truefalsefalse-145000000-145000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accounts payable71false 7so_IncreaseDecreaseInAccruedTaxesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse6000000060000000USD$falsefalsefalse2truefalsefalse128000000128000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes.No definition available.false2-Accrued taxes72false 7us-gaap_IncreaseDecreaseInAccruedSalariesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-54000000-54000000USD$falsefalsefalse2truefalsefalse-45000000-45000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the period in accrued salaries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued compensation73false 7so_IncreaseDecreaseRetailFuelCostOverRecoveryShortTermso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse1200000012000000USD$falsefalsefalse2truefalsefalse20000002000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncrease decrease retail fuel cost over recovery short-term.No definition available.false2-Retail fuel cost over recovery - short-term74false 7us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse40000004000000USD$falsefalsefalse2truefalsefalse-11000000-11000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other liabilities used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current liabilities, other noncurrent liabilities, or a combination of other current and noncurrent liabilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current liabilities75false 6us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse679000000679000000USD$falsefalsefalse2truefalsefalse481000000481000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 true2Net cash provided from operating activities76true 4us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Investing Activities:77false 5us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-518000000-518000000USD$falsefalsefalse2truefalsefalse-436000000-436000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Property additions78false 5us-gaap_PaymentsToInvestInDecommissioningFundus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-120000000-120000000USD$falsefalsefalse2truefalsefalse-88000000-88000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for the purchase of investments that will be held in a decommissioning trust fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Nuclear decommissioning trust fund purchases79false 5us-gaap_ProceedsFromDecommissioningFundus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse120000000120000000USD$falsefalsefalse2truefalsefalse8800000088000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from the sale of assets held in a decommissioning trust fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 false2Nuclear decommissioning trust fund sales80false 5us-gaap_PaymentsForProceedsFromRemovalCostsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-19000000-19000000USD$falsefalsefalse2truefalsefalse-7000000-7000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from the costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, and so forth during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 false2Cost of removal, net of salvage81false 5so_ChangeInConstructionPayablesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-21000000-21000000USD$falsefalsefalse2truefalsefalse-12000000-12000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities.No definition available.false2Change in construction payables82false 5us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse3000000030000000USD$falsefalsefalse2truefalsefalse-9000000-9000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other investing activities83false 5us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-528000000-528000000USD$falsefalsefalse2truefalsefalse-464000000-464000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash used for investing activities84true 4us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financing Activities:85false 5us-gaap_ProceedsFromRepaymentsOfShortTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse4600000046000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Increase (decrease) in notes payable, net86true 5so_ProceedsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Proceeds --87false 6us-gaap_ProceedsFromContributionsFromParentus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1000000010000000USD$falsefalsefalse2truefalsefalse1100000011000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from parent as a source of financing that is recorded as additional paid in capital.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Capital contributions from parent company88false 6us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse250000000250000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Senior notes issuances89true 5so_RedemptionsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Redemptions --90false 6us-gaap_RepaymentsOfPollutionControlBondus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-1000000-1000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow from settlement of a long-term debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Pollution control revenue bonds91false 6us-gaap_RepaymentsOfSeniorDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-250000000-250000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Senior notes92false 5us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-20000000-20000000USD$falsefalsefalse2truefalsefalse-20000000-20000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of preferred and preference stock dividends93false 5us-gaap_PaymentsOfDividendsCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-265000000-265000000USD$falsefalsefalse2truefalsefalse-270000000-270000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of common stock dividends94false 5us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-3000000-3000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other financing activities95false 5us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-229000000-229000000USD$falsefalsefalse2truefalsefalse-283000000-283000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash provided from (used for) financing activities96false 4us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-78000000-78000000USD$falsefalsefalse2truefalsefalse-266000000-266000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 true2Net Change in Cash and Cash Equivalents97false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse137000000137000000USD$falsefalsefalse2truefalsefalse344000000344000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at Beginning of Period98false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsetruefalseperiodEndLabel1truefalsefalse5900000059000000USD$falsefalsefalse2truefalsefalse7800000078000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at End of Period99true 5so_CashPaidReceivedDuringPeriodAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cash paid (received) during the period for --100false 6us-gaap_InterestPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse119000000119000000USD$falsefalsefalse2truefalsefalse136000000136000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid for interest during the period net of cash paid for interest that is capitalized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Interest (net of capitalized amounts)101false 6us-gaap_IncomeTaxesPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse146000000146000000USD$falsefalsefalse2truefalsefalse3100000031000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Income taxes, net102false 4us-gaap_CapitalExpendituresIncurredButNotYetPaidus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1000000010000000USD$falsefalsefalse2truefalsefalse70000007000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFuture cash outflow to pay for purchases of fixed assets that have occurred.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 false2Noncash transactions - accrued property additions at end of period103false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse9false USDtruefalse$D2013Q2_dei_LegalEntityAxis_so_GeorgiaPowerMemberhttp://www.sec.gov/CIK0000092122duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseGeorgia Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_GeorgiaPowerMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Georgia Power [Member]104true 4us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Activities:105false 5us-gaap_ProfitLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse488000000488000000USD$falsefalsefalse2truefalsefalse471000000471000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 false2Consolidated net income106true 5us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Adjustments to reconcile consolidated net income to net cash provided from operating activities --107false 6us-gaap_DepreciationAmortizationAndAccretionNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse487000000487000000USD$falsefalsefalse2truefalsefalse458000000458000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Depreciation and amortization, total108false 6us-gaap_DeferredIncomeTaxExpenseBenefitus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse126000000126000000USD$falsefalsefalse2truefalsefalse128000000128000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Deferred Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6510177 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 false2Deferred income taxes109false 6us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-13000000-13000000USD$falsefalsefalse2truefalsefalse-26000000-26000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 false2Allowance for equity funds used during construction110false 6so_RetailFuelCostOverRecoveryLongTermso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-123000000-123000000USD$falsefalsefalse2truefalsefalse4400000044000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRetail fuel cost over recovery long term.No definition available.false2Retail fuel cost over recovery - long-term111false 6so_RecognitionOfDeferredExpensesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse3100000031000000USD$falsefalsefalse2truefalsefalse2600000026000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRecognition of deferred expenses.No definition available.false2Deferred expenses112false 6us-gaap_OtherNoncashIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-8000000-8000000USD$falsefalsefalse2truefalsefalse-3000000-3000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Other, net113true 6us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Changes in certain current assets and liabilities --114false 7us-gaap_IncreaseDecreaseInReceivablesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-123000000-123000000USD$falsefalsefalse2truefalsefalse1900000019000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Receivables115false 7us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse5600000056000000USD$falsefalsefalse2truefalsefalse-147000000-147000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Fossil fuel stock116false 7us-gaap_IncreaseDecreaseInPrepaidTaxesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse50000005000000USD$falsefalsefalse2truefalsefalse1300000013000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) of consideration paid in advance for income and other taxes that provide economic benefits in future periods.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Prepaid income taxes117false 7us-gaap_IncreaseDecreaseInOtherOperatingAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse3400000034000000USD$falsefalsefalse2truefalsefalse80000008000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other assets used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current assets, other noncurrent assets, or a combination of other current and noncurrent assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current assets118false 7us-gaap_IncreaseDecreaseInAccountsPayableus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse4300000043000000USD$falsefalsefalse2truefalsefalse-37000000-37000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accounts payable119false 7so_IncreaseDecreaseInAccruedTaxesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-14000000-14000000USD$falsefalsefalse2truefalsefalse-77000000-77000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes.No definition available.false2-Accrued taxes120false 7us-gaap_IncreaseDecreaseInAccruedSalariesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-66000000-66000000USD$falsefalsefalse2truefalsefalse-60000000-60000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the period in accrued salaries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued compensation121false 7so_IncreaseDecreaseRetailFuelCostOverRecoveryShortTermso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse10000001000000USD$falsefalsefalse2truefalsefalse5500000055000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncrease decrease retail fuel cost over recovery short-term.No definition available.false2-Retail fuel cost over recovery - short-term122false 7us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse70000007000000USD$falsefalsefalse2truefalsefalse4300000043000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other liabilities used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current liabilities, other noncurrent liabilities, or a combination of other current and noncurrent liabilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current liabilities123false 6us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse931000000931000000USD$falsefalsefalse2truefalsefalse915000000915000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 true2Net cash provided from operating activities124true 4us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Investing Activities:125false 5us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-765000000-765000000USD$falsefalsefalse2truefalsefalse-812000000-812000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Property additions126false 5so_PaymentsForInvestmentInRestrictedCashso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-18000000-18000000USD$falsefalsefalse2truefalsefalse-234000000-234000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryPayments for investment in restricted cash.No definition available.false2Investment of restricted cash127false 5so_ProceedsFromDistributionOfRestrictedCashso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1800000018000000USD$falsefalsefalse2truefalsefalse4900000049000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryProceeds From Distribution Of Restricted CashNo definition available.false2Distribution of restricted cash128false 5us-gaap_PaymentsToInvestInDecommissioningFundus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-427000000-427000000USD$falsefalsefalse2truefalsefalse-488000000-488000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for the purchase of investments that will be held in a decommissioning trust fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Nuclear decommissioning trust fund purchases129false 5us-gaap_ProceedsFromDecommissioningFundus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse426000000426000000USD$falsefalsefalse2truefalsefalse486000000486000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from the sale of assets held in a decommissioning trust fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 false2Nuclear decommissioning trust fund sales130false 5us-gaap_PaymentsForProceedsFromRemovalCostsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-27000000-27000000USD$falsefalsefalse2truefalsefalse-34000000-34000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from the costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, and so forth during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 false2Cost of removal, net of salvage131false 5so_ChangeInConstructionPayablesNetOfJointOwnerPortionso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-2000000-2000000USD$falsefalsefalse2truefalsefalse-161000000-161000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle) net of joint owner portion. This includes accounts payable related to construction activities.No definition available.false2Change in construction payables, net of joint owner portion132false 5us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-12000000-12000000USD$falsefalsefalse2truefalsefalse-14000000-14000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other investing activities133false 5us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-807000000-807000000USD$falsefalsefalse2truefalsefalse-1208000000-1208000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash used for investing activities134true 4us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financing Activities:135false 5us-gaap_ProceedsFromRepaymentsOfShortTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse314000000314000000USD$falsefalsefalse2truefalsefalse-513000000-513000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Increase (decrease) in notes payable, net136true 5so_ProceedsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Proceeds --137false 6us-gaap_ProceedsFromContributionsFromParentus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2100000021000000USD$falsefalsefalse2truefalsefalse1800000018000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from parent as a source of financing that is recorded as additional paid in capital.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Capital contributions from parent company138false 6us-gaap_ProceedsFromPollutionControlBondus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1800000018000000USD$falsefalsefalse2truefalsefalse234000000234000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from amounts received from a long-term debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Pollution control revenue bonds issuances139false 6us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse650000000650000000USD$falsefalsefalse2truefalsefalse15000000001500000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Senior notes issuances140true 5so_RedemptionsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Redemptions --141false 6us-gaap_RepaymentsOfPollutionControlBondus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-18000000-18000000USD$falsefalsefalse2truefalsefalse-49000000-49000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow from settlement of a long-term debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Pollution control revenue bonds142false 6us-gaap_RepaymentsOfSeniorDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-650000000-650000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Senior notes143false 6us-gaap_RepaymentsOfOtherLongTermDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-250000000-250000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow attributable to repayments of borrowings not otherwise defined in the taxonomy (with maturities initially due after one year or beyond the operating cycle if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Other long-term debt144false 5us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-9000000-9000000USD$falsefalsefalse2truefalsefalse-9000000-9000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of preferred and preference stock dividends145false 5us-gaap_PaymentsOfDividendsCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-454000000-454000000USD$falsefalsefalse2truefalsefalse-454000000-454000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of common stock dividends146false 5us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-12000000-12000000USD$falsefalsefalse2truefalsefalse-9000000-9000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other financing activities147false 5us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-140000000-140000000USD$falsefalsefalse2truefalsefalse468000000468000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash provided from (used for) financing activities148false 4us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-16000000-16000000USD$falsefalsefalse2truefalsefalse175000000175000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 true2Net Change in Cash and Cash Equivalents149false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse4500000045000000USD$falsefalsefalse2truefalsefalse1300000013000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at Beginning of Period150false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsetruefalseperiodEndLabel1truefalsefalse2900000029000000USD$falsefalsefalse2truefalsefalse188000000188000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at End of Period151true 5so_CashPaidReceivedDuringPeriodAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cash paid (received) during the period for --152false 6us-gaap_InterestPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse169000000169000000USD$falsefalsefalse2truefalsefalse156000000156000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid for interest during the period net of cash paid for interest that is capitalized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Interest (net of capitalized amounts)153false 6us-gaap_IncomeTaxesPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse100000000100000000USD$falsefalsefalse2truefalsefalse4400000044000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Income taxes, net154false 4us-gaap_CapitalExpendituresIncurredButNotYetPaidus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse238000000238000000USD$falsefalsefalse2truefalsefalse234000000234000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFuture cash outflow to pay for purchases of fixed assets that have occurred.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 false2Noncash transactions - accrued property additions at end of period155false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse13false USDtruefalse$D2013Q2_dei_LegalEntityAxis_so_GulfPowerMemberhttp://www.sec.gov/CIK0000092122duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseGulf Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_GulfPowerMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Gulf Power [Member]156true 4us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Activities:157false 5us-gaap_ProfitLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse5757600057576000USD$falsefalsefalse2truefalsefalse5873000058730000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 false2Consolidated net income158true 5us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Adjustments to reconcile consolidated net income to net cash provided from operating activities --159false 6us-gaap_DepreciationAmortizationAndAccretionNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse7762700077627000USD$falsefalsefalse2truefalsefalse7170700071707000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Depreciation and amortization, total160false 6us-gaap_DeferredIncomeTaxExpenseBenefitus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse3640700036407000USD$falsefalsefalse2truefalsefalse7015300070153000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Deferred Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6510177 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 false2Deferred income taxes161false 6us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-2655000-2655000USD$falsefalsefalse2truefalsefalse-2973000-2973000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 false2Allowance for equity funds used during construction162false 6us-gaap_PensionAndOtherPostretirementBenefitExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse54520005452000USD$falsefalsefalse2truefalsefalse23830002383000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 false2Pension, postretirement, and other employee benefits163false 6us-gaap_StockOptionPlanExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse10280001028000USD$falsefalsefalse2truefalsefalse10440001044000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Stock based compensation expense164false 6us-gaap_OtherNoncashIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse22090002209000USD$falsefalsefalse2truefalsefalse75030007503000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Other, net165true 6us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Changes in certain current assets and liabilities --166false 7us-gaap_IncreaseDecreaseInReceivablesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-59770000-59770000USD$falsefalsefalse2truefalsefalse-18580000-18580000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Receivables167false 7us-gaap_IncreaseDecreaseInPrepaidExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse12710001271000USD$falsefalsefalse2truefalsefalse18130001813000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the amount of outstanding money paid in advance for goods or services that bring economic benefits for future periods.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Prepayments168false 7us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse1933200019332000USD$falsefalsefalse2truefalsefalse39820003982000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Fossil fuel stock169false 7us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-987000-987000USD$falsefalsefalse2truefalsefalse-4100000-4100000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Materials and supplies170false 7us-gaap_IncreaseDecreaseInPrepaidTaxesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-2822000-2822000USD$falsefalsefalse2truefalsefalse-3566000-3566000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) of consideration paid in advance for income and other taxes that provide economic benefits in future periods.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Prepaid income taxes171false 7us-gaap_IncreaseDecreaseInOtherCurrentAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse1300013000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other current operating assets not separately disclosed in the statement of cash flows.No definition available.false2-Other current assets172false 7us-gaap_IncreaseDecreaseInAccountsPayableus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-9703000-9703000USD$falsefalsefalse2truefalsefalse-17481000-17481000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accounts payable173false 7so_IncreaseDecreaseInAccruedTaxesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1363200013632000USD$falsefalsefalse2truefalsefalse67880006788000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes.No definition available.false2-Accrued taxes174false 7us-gaap_IncreaseDecreaseInAccruedSalariesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-8308000-8308000USD$falsefalsefalse2truefalsefalse-6239000-6239000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the period in accrued salaries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued compensation175false 7so_OverRecoveredRegulatoryClauseso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-15659000-15659000USD$falsefalsefalse2truefalsefalse2509900025099000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncrease or decrease in over recovered regulatory clause revenues on the cash flow.No definition available.false2-Over recovered regulatory clause revenues176false 7us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-1199000-1199000USD$falsefalsefalse2truefalsefalse-1659000-1659000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other liabilities used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current liabilities, other noncurrent liabilities, or a combination of other current and noncurrent liabilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current liabilities177false 6us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse113444000113444000USD$falsefalsefalse2truefalsefalse194604000194604000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 true2Net cash provided from operating activities178true 4us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Investing Activities:179false 5us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-137283000-137283000USD$falsefalsefalse2truefalsefalse-169462000-169462000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Property additions180false 5us-gaap_PaymentsForProceedsFromRemovalCostsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-7010000-7010000USD$falsefalsefalse2truefalsefalse-14817000-14817000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from the costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, and so forth during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 false2Cost of removal, net of salvage181false 5so_ChangeInConstructionPayablesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse63070006307000USD$falsefalsefalse2truefalsefalse36610003661000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities.No definition available.false2Change in construction payables182false 5so_PaymentsPursuantToLongTermServiceAgreementsso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-2855000-2855000USD$falsefalsefalse2truefalsefalse-4086000-4086000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryPayments pursuant to long-term service agreements.No definition available.false2Payments pursuant to long-term service agreements183false 5us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse120000120000USD$falsefalsefalse2truefalsefalse1800018000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other investing activities184false 5us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-140721000-140721000USD$falsefalsefalse2truefalsefalse-184686000-184686000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash used for investing activities185true 4us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financing Activities:186false 5us-gaap_ProceedsFromRepaymentsOfShortTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse12300001230000USD$falsefalsefalse2truefalsefalse59800005980000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Increase (decrease) in notes payable, net187true 5so_ProceedsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Proceeds --188false 6us-gaap_ProceedsFromContributionsFromParentus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse14190001419000USD$falsefalsefalse2truefalsefalse954000954000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from parent as a source of financing that is recorded as additional paid in capital.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Capital contributions from parent company189false 6us-gaap_ProceedsFromPollutionControlBondus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse6300000063000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from amounts received from a long-term debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Pollution control revenue bonds issuances190false 6us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStockus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5000000050000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryProceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Preference stock191false 6us-gaap_ProceedsFromIssuanceOfCommonStockus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse4000000040000000USD$falsefalsefalse2truefalsefalse4000000040000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from the additional capital contribution to the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Common stock issuances192false 6us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse9000000090000000USD$falsefalsefalse2truefalsefalse100000000100000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Senior notes issuances193true 5so_RedemptionsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Redemptions --194false 6us-gaap_RepaymentsOfPollutionControlBondus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-63000000-63000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow from settlement of a long-term debt security issued by a state, certain agencies or authorities, a local government, or development corporation to finance the construction of air- or water-pollution control facilities or sewage or solid waste disposal facilities pursuant to federal law. The bonds are backed by the credit of the beneficiary of the financing rather than the credit of the issuer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Pollution control revenue bonds195false 6us-gaap_RepaymentsOfSeniorDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-91363000-91363000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Senior notes196false 5us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-3101000-3101000USD$falsefalsefalse2truefalsefalse-3101000-3101000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of preferred and preference stock dividends197false 5us-gaap_PaymentsOfDividendsCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-57700000-57700000USD$falsefalsefalse2truefalsefalse-57900000-57900000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of common stock dividends198false 5us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-3105000-3105000USD$falsefalsefalse2truefalsefalse-653000-653000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other financing activities199false 5us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse118743000118743000USD$falsefalsefalse2truefalsefalse-6083000-6083000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash provided from (used for) financing activities200false 4us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse9146600091466000USD$falsefalsefalse2truefalsefalse38350003835000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 true2Net Change in Cash and Cash Equivalents201false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse3216700032167000USD$falsefalsefalse2truefalsefalse1732800017328000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at Beginning of Period202false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsetruefalseperiodEndLabel1truefalsefalse123633000123633000USD$falsefalsefalse2truefalsefalse2116300021163000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at End of Period203true 5so_CashPaidReceivedDuringPeriodAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cash paid (received) during the period for --204false 6us-gaap_InterestPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2698700026987000USD$falsefalsefalse2truefalsefalse3010000030100000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid for interest during the period net of cash paid for interest that is capitalized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Interest (net of capitalized amounts)205false 6us-gaap_IncomeTaxesPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse428000428000USD$falsefalsefalse2truefalsefalse-32848000-32848000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Income taxes, net206false 4us-gaap_CapitalExpendituresIncurredButNotYetPaidus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2903600029036000USD$falsefalsefalse2truefalsefalse2712700027127000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFuture cash outflow to pay for purchases of fixed assets that have occurred.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 false2Noncash transactions - accrued property additions at end of period207false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse17false USDtruefalse$D2013Q2_dei_LegalEntityAxis_so_MississippiPowerMemberhttp://www.sec.gov/CIK0000092122duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseMississippi Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_MississippiPowerMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Mississippi Power [Member]208true 4us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Activities:209false 5us-gaap_ProfitLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-464565000-464565000USD$falsefalsefalse2truefalsefalse6114800061148000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 false2Consolidated net income210true 5us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Adjustments to reconcile consolidated net income to net cash provided from operating activities --211false 6us-gaap_DepreciationAmortizationAndAccretionNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse4326300043263000USD$falsefalsefalse2truefalsefalse4395500043955000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Depreciation and amortization, total212false 6us-gaap_DeferredIncomeTaxExpenseBenefitus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-337167000-337167000USD$falsefalsefalse2truefalsefalse12800001280000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Deferred Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6510177 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 false2Deferred income taxes213false 6us-gaap_InvestmentTaxCreditus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse6647400066474000USD$falsefalsefalse2truefalsefalse1397400013974000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; includes deferred investment tax credits.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Investment tax credits214false 6us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquityus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-55116000-55116000USD$falsefalsefalse2truefalsefalse-25697000-25697000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501662&loc=d3e56162-110433 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 835 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501569&loc=d3e55921-110430 false2Allowance for equity funds used during construction215false 6us-gaap_PensionAndOtherPostretirementBenefitExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse61840006184000USD$falsefalsefalse2truefalsefalse39930003993000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 false2Pension, postretirement, and other employee benefits216false 6so_HedgeSettlementsso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-15983000-15983000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow (inflow) for a financial contract that settles in the period relating to operating activities.No definition available.false2Hedge settlements217false 6us-gaap_StockOptionPlanExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse15470001547000USD$falsefalsefalse2truefalsefalse13440001344000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Stock based compensation expense218false 6so_RegulatoryAssetsAssociatedWithIntegratedCoalGasificationCombinedCycleProjectso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-13399000-13399000USD$falsefalsefalse2truefalsefalse-6431000-6431000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncrease or (decrease) during reporting period of regulatory assets used in operating activities associated with the Integrated Coal Gasification Combined Cycle.No definition available.false2Regulatory assets associated with Kemper IGCC219false 6so_EstimatedLossOnIntegratedCoalGasificationCombinedCycleProjectso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse912000000912000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEstimated Loss On Integrated Coal Gasification Combined Cycle ProjectNo definition available.false2Estimated loss on Kemper IGCC220false 6so_IntegratedCoalGasificationCombinedCycleRegulatoryDeferralso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2697900026979000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIntegrated Coal Gasification Combined Cycle Regulatory DeferralNo definition available.false2Kemper regulatory deferral221false 6us-gaap_OtherNoncashIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse10680001068000USD$falsefalsefalse2truefalsefalse37830003783000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Other, net222true 6us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Changes in certain current assets and liabilities --223false 7us-gaap_IncreaseDecreaseInReceivablesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-37431000-37431000USD$falsefalsefalse2truefalsefalse-12424000-12424000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Receivables224false 7us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse3420500034205000USD$falsefalsefalse2truefalsefalse-32797000-32797000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Fossil fuel stock225false 7us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-6509000-6509000USD$falsefalsefalse2truefalsefalse212000212000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Materials and supplies226false 7us-gaap_IncreaseDecreaseInPrepaidTaxesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse88230008823000USD$falsefalsefalse2truefalsefalse1197400011974000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) of consideration paid in advance for income and other taxes that provide economic benefits in future periods.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Prepaid income taxes227false 7us-gaap_IncreaseDecreaseInOtherOperatingAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-4879000-4879000USD$falsefalsefalse2truefalsefalse-7281000-7281000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other assets used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current assets, other noncurrent assets, or a combination of other current and noncurrent assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current assets228false 7us-gaap_IncreaseDecreaseInAccountsPayableus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-5417000-5417000USD$falsefalsefalse2truefalsefalse34080003408000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accounts payable229false 7so_IncreaseDecreaseInAccruedTaxesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-24101000-24101000USD$falsefalsefalse2truefalsefalse-16785000-16785000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes.No definition available.false2-Accrued taxes230false 7us-gaap_IncreaseDecreaseInInterestPayableNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse85020008502000USD$falsefalsefalse2truefalsefalse73460007346000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in interest payable, which represents the amount owed to note holders, bond holders, and other parties for interest earned on loans or credit extended to the reporting entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued interest231false 7us-gaap_IncreaseDecreaseInAccruedSalariesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-10461000-10461000USD$falsefalsefalse2truefalsefalse-7002000-7002000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the period in accrued salaries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued compensation232false 7so_OverRecoveredRegulatoryClauseso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-27838000-27838000USD$falsefalsefalse2truefalsefalse1587100015871000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryIncrease or decrease in over recovered regulatory clause revenues on the cash flow.No definition available.false2-Over recovered regulatory clause revenues233false 7us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse282000282000USD$falsefalsefalse2truefalsefalse294000294000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other liabilities used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current liabilities, other noncurrent liabilities, or a combination of other current and noncurrent liabilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current liabilities234false 6us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse122444000122444000USD$falsefalsefalse2truefalsefalse4418200044182000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 true2Net cash provided from operating activities235true 4us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Investing Activities:236false 5us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-789021000-789021000USD$falsefalsefalse2truefalsefalse-763641000-763641000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Property additions237false 5us-gaap_PaymentsForProceedsFromRemovalCostsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-2033000-2033000USD$falsefalsefalse2truefalsefalse-1217000-1217000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from the costs of disposing of plant, whether by demolishing, dismantling, abandoning, sale, and so forth during the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 false2Cost of removal, net of salvage238false 5so_ChangeInConstructionPayablesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2331400023314000USD$falsefalsefalse2truefalsefalse5728300057283000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities.No definition available.false2Change in construction payables239false 5so_ProceedsFromCapitalGrantso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse45000004500000USD$falsefalsefalse2truefalsefalse61460006146000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryProceeds from capital grant.No definition available.false2Capital grant proceeds240false 5us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-11172000-11172000USD$falsefalsefalse2truefalsefalse-9690000-9690000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other investing activities241false 5us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-774412000-774412000USD$falsefalsefalse2truefalsefalse-711119000-711119000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash used for investing activities242true 5so_ProceedsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Proceeds --243false 6us-gaap_ProceedsFromContributionsFromParentus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse351198000351198000USD$falsefalsefalse2truefalsefalse277633000277633000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from parent as a source of financing that is recorded as additional paid in capital.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Capital contributions from parent company244false 6so_ProceedsFromBondsOtherso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1581400015814000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryProceeds From Bonds OtherNo definition available.false2Bonds-Other245false 6so_InterestBearingRefundableDepositRelatedToAssetSaleso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse150000000150000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryInterest bearing refundable deposit related to asset sale.No definition available.false2Interest-bearing refundable deposit related to asset sale246false 6us-gaap_ProceedsFromIssuanceOfSeniorLongTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse400000000400000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Senior notes issuances247false 6us-gaap_ProceedsFromIssuanceOfOtherLongTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse350000000350000000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from other long-term borrowings not otherwise defined in the taxonomy (with maturities initially due beyond one year or the normal operating cycle of the entity, if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Other long-term debt issuances248true 5so_RedemptionsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Redemptions --249false 6us-gaap_RepaymentsOfDebtAndCapitalLeaseObligationsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-633000-633000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow during the period from the repayment of aggregate short-term and long-term debt and payment of capital lease obligations.No definition available.false2Capital leases250false 6us-gaap_RepaymentsOfOtherLongTermDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse-165000000-165000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow attributable to repayments of borrowings not otherwise defined in the taxonomy (with maturities initially due after one year or beyond the operating cycle if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Other long-term debt251false 5so_ReturnOfPaidInCapitalso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-16424000-16424000USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryReturn Of Paid In CapitalNo definition available.false2Return of paid in capital252false 5us-gaap_PaymentsOfDividendsPreferredStockAndPreferenceStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-866000-866000USD$falsefalsefalse2truefalsefalse-866000-866000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to preferred shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of preferred and preference stock dividends253false 5us-gaap_PaymentsOfDividendsCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-71956000-71956000USD$falsefalsefalse2truefalsefalse-53400000-53400000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of common stock dividends254false 5us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-1431000-1431000USD$falsefalsefalse2truefalsefalse998000998000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other financing activities255false 5us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse626335000626335000USD$falsefalsefalse2truefalsefalse608732000608732000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash provided from (used for) financing activities256false 4us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-25633000-25633000USD$falsefalsefalse2truefalsefalse-58205000-58205000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 true2Net Change in Cash and Cash Equivalents257false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse145008000145008000USD$falsefalsefalse2truefalsefalse211585000211585000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at Beginning of Period258false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsetruefalseperiodEndLabel1truefalsefalse119375000119375000USD$falsefalsefalse2truefalsefalse153380000153380000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at End of Period259true 5so_CashPaidReceivedDuringPeriodAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cash paid (received) during the period for --260false 6us-gaap_InterestPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1342300013423000USD$falsefalsefalse2truefalsefalse1660300016603000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid for interest during the period net of cash paid for interest that is capitalized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Interest (net of capitalized amounts)261false 6us-gaap_IncomeTaxesPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-64062000-64062000USD$falsefalsefalse2truefalsefalse-7756000-7756000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Income taxes, net262false 4us-gaap_CapitalExpendituresIncurredButNotYetPaidus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse238177000238177000USD$falsefalsefalse2truefalsefalse193184000193184000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFuture cash outflow to pay for purchases of fixed assets that have occurred.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 false2Noncash transactions - accrued property additions at end of period263false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse21false USDtruefalse$D2013Q2_dei_LegalEntityAxis_so_SouthernPowerMemberhttp://www.sec.gov/CIK0000092122duration2013-04-01T00:00:002013-06-30T00:00:00falsefalseSouthern Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_SouthernPowerMemberdei_LegalEntityAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Southern Power [Member]264true 4us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Operating Activities:265false 5us-gaap_ProfitLossus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse5711400057114000USD$falsefalsefalse2truefalsefalse7591800075918000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591552-111686 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a),(c) -URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=31814832&loc=SL4591551-111686 false2Consolidated net income266true 5us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Adjustments to reconcile consolidated net income to net cash provided from operating activities --267false 6us-gaap_DepreciationAmortizationAndAccretionNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse9035100090351000USD$falsefalsefalse2truefalsefalse7183400071834000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe aggregate net amount of depreciation, amortization, and accretion recognized during an accounting period. As a noncash item, the net amount is added back to net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Depreciation and amortization, total268false 6us-gaap_DeferredIncomeTaxExpenseBenefitus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1369300013693000USD$falsefalsefalse2truefalsefalse5892100058921000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.7) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section I -Subsection 7 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Deferred Tax Expense (or Benefit) -URI http://asc.fasb.org/extlink&oid=6510177 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319 false2Deferred income taxes269false 6us-gaap_InvestmentTaxCreditus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1644300016443000USD$falsefalsefalse2truefalsefalse17500001750000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; includes deferred investment tax credits.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Investment tax credits270false 6us-gaap_RecognitionOfDeferredRevenueus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-23444000-23444000USD$falsefalsefalse2truefalsefalse-16431000-16431000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of previously reported deferred or unearned revenue that was recognized as revenue during the period. For cash flows, this element primarily pertains to amortization of deferred credits on long-term arrangements. As a noncash item, it is deducted from net income when calculating cash provided by or used in operations using the indirect method.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 13.A.4(a).Q1) -URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section A -Subsection 1 false2Deferred revenues271false 6us-gaap_DerivativeGainLossOnDerivativeNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-40000-40000USD$falsefalsefalse2truefalsefalse-3847000-3847000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in the fair value of derivatives recognized in the income statement.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5618551-113959 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a),(c),(d),(e) -URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959 false2Mark-to-market adjustments272false 6us-gaap_OtherNoncashIncomeExpenseus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse1194900011949000USD$falsefalsefalse2truefalsefalse19270001927000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryOther income (expense) included in net income that results in no cash inflows or outflows in the period. Includes noncash adjustments to reconcile net income (loss) to cash provided by (used in) operating activities that are not separately disclosed.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2Other, net273true 6us-gaap_IncreaseDecreaseInOperatingCapitalAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Changes in certain current assets and liabilities --274false 7us-gaap_IncreaseDecreaseInReceivablesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-23335000-23335000USD$falsefalsefalse2truefalsefalse-30101000-30101000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the total amount due within one year (or one operating cycle) from all parties, associated with underlying transactions that are classified as operating activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Receivables275false 7us-gaap_IncreaseDecreaseInFossilFuelInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-377000-377000USD$falsefalsefalse2truefalsefalse-3301000-3301000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of fossil fuel held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Fossil fuel stock276false 7us-gaap_IncreaseDecreaseInRawMaterialsPackagingMaterialsAndSuppliesInventoriesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-2560000-2560000USD$falsefalsefalse2truefalsefalse-7761000-7761000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the value of raw materials, packaging materials and supplies held in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Materials and supplies277false 7us-gaap_IncreaseDecreaseInPrepaidTaxesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-19747000-19747000USD$falsefalsefalse2truefalsefalse-32804000-32804000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) of consideration paid in advance for income and other taxes that provide economic benefits in future periods.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Prepaid income taxes278false 7us-gaap_IncreaseDecreaseInOtherOperatingAssetsus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse27250002725000USD$falsefalsefalse2truefalsefalse-377000-377000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other assets used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current assets, other noncurrent assets, or a combination of other current and noncurrent assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current assets279false 7us-gaap_IncreaseDecreaseInAccountsPayableus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-7580000-7580000USD$falsefalsefalse2truefalsefalse-494000-494000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accounts payable280false 7so_IncreaseDecreaseInAccruedTaxesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2104800021048000USD$falsefalsefalse2truefalsefalse1329500013295000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the period in the amount of cash payments due to taxing authorities for income and non income-related taxes.No definition available.false2-Accrued taxes281false 7us-gaap_IncreaseDecreaseInInterestPayableNetus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-41000-41000USD$falsefalsefalse2truefalsefalse409000409000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in interest payable, which represents the amount owed to note holders, bond holders, and other parties for interest earned on loans or credit extended to the reporting entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Accrued interest282false 7us-gaap_IncreaseDecreaseInOtherOperatingLiabilitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse-390000-390000USD$falsefalsefalse2truefalsefalse-195000-195000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe increase (decrease) during the reporting period in other liabilities used in operating activities not separately disclosed in the statement of cash flows. May include changes in other current liabilities, other noncurrent liabilities, or a combination of other current and noncurrent liabilities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 false2-Other current liabilities283false 6us-gaap_NetCashProvidedByUsedInOperatingActivitiesus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse135809000135809000USD$falsefalsefalse2truefalsefalse128743000128743000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 true2Net cash provided from operating activities284true 4us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Investing Activities:285false 5us-gaap_PaymentsToAcquireOtherPropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedTerseLabel1truefalsefalse-111600000-111600000USD$falsefalsefalse2truefalsefalse-86500000-86500000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow for acquisition of or capital improvements of property, plant and equipment, used to produce goods or deliver services, and not otherwise defined in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Plant acquisition286false 5us-gaap_PaymentsToAcquirePropertyPlantAndEquipmentus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-252271000-252271000USD$falsefalsefalse2truefalsefalse-67846000-67846000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 false2Property additions287false 5so_PaymentsForInvestmentInRestrictedCashso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-20000000-20000000USD$falsefalsefalse2truefalsefalse30150003015000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryPayments for investment in restricted cash.No definition available.false2Investment of restricted cash288false 5so_ChangeInConstructionPayablesso_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse106795000106795000USD$falsefalsefalse2truefalsefalse-1168000-1168000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net change during the reporting period in the aggregate amount of construction obligations due within one year (or one business cycle). This includes accounts payable related to construction activities.No definition available.false2Change in construction payables289false 5so_PaymentsPursuantToLongTermServiceAgreementsso_falsecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-22469000-22469000USD$falsefalsefalse2truefalsefalse-36316000-36316000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryPayments pursuant to long-term service agreements.No definition available.false2Payments pursuant to long-term service agreements290false 5us-gaap_PaymentsForProceedsFromOtherInvestingActivitiesus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-206000-206000USD$falsefalsefalse2truefalsefalse-2862000-2862000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash outflow or inflow from other investing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other investing activities291false 5us-gaap_NetCashProvidedByUsedInInvestingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-299751000-299751000USD$falsefalsefalse2truefalsefalse-191677000-191677000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash used for investing activities292true 4us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Financing Activities:293false 5us-gaap_ProceedsFromRepaymentsOfShortTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse195142000195142000USD$falsefalsefalse2truefalsefalse107147000107147000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Increase (decrease) in notes payable, net294true 5so_ProceedsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Proceeds --295false 6us-gaap_ProceedsFromContributionsFromParentus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse13940001394000USD$falsefalsefalse2truefalsefalse490000490000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from parent as a source of financing that is recorded as additional paid in capital.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Capital contributions from parent company296false 6us-gaap_ProceedsFromIssuanceOfOtherLongTermDebtus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse1024900010249000USD$falsefalsefalse2truefalsefalse35900003590000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash inflow from other long-term borrowings not otherwise defined in the taxonomy (with maturities initially due beyond one year or the normal operating cycle of the entity, if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 false2Other long-term debt issuances297true 5so_RedemptionsAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Redemptions --298false 6us-gaap_RepaymentsOfOtherLongTermDebtus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-220000-220000USD$falsefalsefalse2truefalsefalse-650000-650000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe cash outflow attributable to repayments of borrowings not otherwise defined in the taxonomy (with maturities initially due after one year or beyond the operating cycle if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 false2Other long-term debt299false 5us-gaap_PaymentsOfDividendsCommonStockus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-64560000-64560000USD$falsefalsefalse2truefalsefalse-63500000-63500000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 false2Payment of common stock dividends300false 5us-gaap_ProceedsFromPaymentsForOtherFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse82120008212000USD$falsefalsefalse2truefalsefalse27460002746000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 false2Other financing activities301false 5us-gaap_NetCashProvidedByUsedInFinancingActivitiesus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse150217000150217000USD$falsefalsefalse2truefalsefalse4982300049823000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 true2Net cash provided from (used for) financing activities302false 4us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsetotalLabel1truefalsefalse-13725000-13725000USD$falsefalsefalse2truefalsefalse-13111000-13111000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 true2Net Change in Cash and Cash Equivalents303false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsetruefalsefalseperiodStartLabel1truefalsefalse2859200028592000USD$falsefalsefalse2truefalsefalse1694300016943000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at Beginning of Period304false 4us-gaap_CashAndCashEquivalentsAtCarryingValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsetruefalseperiodEndLabel1truefalsefalse1486700014867000USD$falsefalsefalse2truefalsefalse38320003832000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryAmount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash -URI http://asc.fasb.org/extlink&oid=6506951 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Cash Equivalents -URI http://asc.fasb.org/extlink&oid=6507016 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6676-107765 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3044-108585 false2Cash and Cash Equivalents at End of Period305true 5so_CashPaidReceivedDuringPeriodAbstractso_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Cash paid (received) during the period for --306false 6us-gaap_InterestPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse3492400034924000USD$falsefalsefalse2truefalsefalse2146100021461000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid for interest during the period net of cash paid for interest that is capitalized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Interest (net of capitalized amounts)307false 6us-gaap_IncomeTaxesPaidNetus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse-3799000-3799000USD$falsefalsefalse2truefalsefalse1370800013708000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586 false2Income taxes, net308false 4us-gaap_CapitalExpendituresIncurredButNotYetPaidus-gaap_truecreditdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse136998000136998000USD$falsetruefalse2truefalsefalse4692200046922000USD$falsetruefalsexbrli:monetaryItemTypemonetaryFuture cash outflow to pay for purchases of fixed assets that have occurred.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586 false2Noncash transactions - accrued property additions at end of periodfalseCondensed Consolidated Statements of Cash Flows (Unaudited) (USD $)NoRoundingUnKnownUnKnownUnKnowntruefalsefalseSheethttp://southerncompany.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited2308