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4us-gaap_LiabilitiesFairValueDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Liabilities:313false 5so_EnergyRelatedDerivativesLiabilitiesFairValueDisclosureso_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEnergy-related derivatives liabilities fair value disclosure.No definition available.false2Energy-related derivatives314false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse76false USDtruefalse$I2013Q2_dei_LegalEntityAxis_so_SouthernPowerMember_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel2Member_us-gaap_FairValueByMeasurementFrequencyAxis_us-gaap_FairValueMeasurementsRecurringMemberhttp://www.sec.gov/CIK0000092122instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSouthern Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_SouthernPowerMemberdei_LegalEntityAxisexplicitMemberfalsefalseFair Value, Measurements, Recurring [Member]us-gaap_FairValueByMeasurementFrequencyAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueMeasurementsRecurringMemberus-gaap_FairValueByMeasurementFrequencyAxisexplicitMemberfalsefalseSignificant Other Observable Inputs (Level 2) [Member]us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel2Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Southern Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]315true 4us-gaap_AssetsFairValueDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Assets:316false 5so_EnergyRelatedDerivativesAssetsFairValueDisclosureso_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse20000002USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEnergy-related derivatives assets fair value disclosure.No definition available.false2Energy-related derivatives317true 4us-gaap_LiabilitiesFairValueDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Liabilities:318false 5so_EnergyRelatedDerivativesLiabilitiesFairValueDisclosureso_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse10000001USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEnergy-related derivatives liabilities fair value disclosure.No definition available.false2Energy-related derivatives319false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse77false USDtruefalse$I2013Q2_dei_LegalEntityAxis_so_SouthernPowerMember_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Member_us-gaap_FairValueByMeasurementFrequencyAxis_us-gaap_FairValueMeasurementsRecurringMemberhttp://www.sec.gov/CIK0000092122instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSouthern Power [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldiso_SouthernPowerMemberdei_LegalEntityAxisexplicitMemberfalsefalseFair Value, Measurements, Recurring [Member]us-gaap_FairValueByMeasurementFrequencyAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueMeasurementsRecurringMemberus-gaap_FairValueByMeasurementFrequencyAxisexplicitMemberfalsefalseSignificant Unobservable Inputs (Level 3) [Member]us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel3Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Southern Power [Member] | Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]320true 4us-gaap_AssetsFairValueDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Assets:321false 5so_EnergyRelatedDerivativesAssetsFairValueDisclosureso_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEnergy-related derivatives assets fair value disclosure.No definition available.false2Energy-related derivatives322true 4us-gaap_LiabilitiesFairValueDisclosureAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Liabilities:323false 5so_EnergyRelatedDerivativesLiabilitiesFairValueDisclosureso_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsetruefalsexbrli:monetaryItemTypemonetaryEnergy-related derivatives liabilities fair value disclosure.No definition available.false2Energy-related derivatives1For additional detail, see the nuclear decommissioning trusts sections for Alabama Power and Georgia Power in this table.2Excludes receivables related to investment income, pending investment sales, and payables related to pending investment purchases.3Includes the investment securities pledged to creditors and cash collateral received and excludes payables related to the securities lending program. As of June 30, 2013, approximately $38 million of the fair market value of Georgia Power's nuclear decommissioning trust funds' securities were on loan and pledged to creditors under the funds' managers' securities lending program.falseFair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (USD $)MillionsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://southerncompany.com/role/FairValueMeasurementsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails1323