XML 1152 R69.htm IDEA: XBRL DOCUMENT v2.4.1.9
Joint Ownership Agreements (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
MW
Dec. 31, 2013
Dec. 31, 2012
Aug. 31, 2014
Joint Ownership Agreements (Textual) [Abstract]        
Short-term Debt $ 803,000,000us-gaap_ShortTermBorrowings $ 1,482,000,000us-gaap_ShortTermBorrowings    
Plant acquisition adjustment 123,000,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1 123,000,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1    
Plant Vogtle (nuclear) Units 1 and 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 45.70%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember		      
Plant in Service 3,420,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember		      
Accumulated Depreciation 2,059,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember		      
Plant Hatch (nuclear) [Member]        
Jointly owned utility plant interests        
Percent Ownership 50.10%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember		      
Plant in Service 1,117,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember		      
Accumulated Depreciation 559,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember		      
Plant Miller (coal) Units 1 and 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 91.80%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember		      
Plant in Service 1,512,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember		      
Accumulated Depreciation 561,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember		      
Plant Scherer (coal) Units 1 and 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 8.40%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember		      
Plant in Service 254,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember		      
Accumulated Depreciation 83,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember		      
Plant Wansley (coal) [Member]        
Jointly owned utility plant interests        
Percent Ownership 53.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember		      
Plant in Service 856,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember		      
Accumulated Depreciation 278,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember		      
Rocky Mountain (pumped storage) [Member]        
Jointly owned utility plant interests        
Percent Ownership 25.40%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember		      
Plant in Service 182,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember		      
Accumulated Depreciation 124,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember		      
Intercession City (combustion turbine) [Member]        
Jointly owned utility plant interests        
Percent Ownership 33.30%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember		      
Plant in Service 14,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember		      
Accumulated Depreciation 5,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember		      
Plant Stanton (combined cycle) Unit A [Member]        
Jointly owned utility plant interests        
Percent Ownership 65.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember		      
Plant in Service 157,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember		      
Accumulated Depreciation 47,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember		      
Alabama Power [Member]        
Jointly owned utility plant interests        
Percent Ownership 14.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 1,000so_ElectricGeneratingUnitsCapacity
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Jointly Owned Affiliate Equity 106,000,000so_JointlyOwnedAffiliateEquity
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Jointly Owned Affiliate Long Term Debt 125,000,000so_JointlyOwnedAffiliateLongTermDebt
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Jointly Owned Affiliate Long Term Debt Annual Interest Requirement 3,000,000so_JointlyOwnedAffiliateLongTermDebtAnnualInterestRequirement
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Dividends paid by equity method investment 3,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		 7,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		 14,000,000us-gaap_EquityMethodInvestmentDividendsOrDistributions
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		  
Ownership percentage, equity method investment 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Plant acquisition adjustment 12,000,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		 12,000,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		    
Alabama Power [Member] | SEGCO [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 1,020so_ElectricGeneratingUnitsCapacity
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		      
Share Of Purchased Power 84,000,000so_ShareOfPurchasedPower
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		 88,000,000so_ShareOfPurchasedPower
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		 109,000,000so_ShareOfPurchasedPower
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		  
Unconditional guarantee to pay outstanding pollution control revenue bond principal 25,000,000so_UnconditionalGuaranteeToPayOutstandingPollutionControlRevenueBondPrincipal
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		      
Guarantee of unsecured senior notes 50,000,000so_GuaranteeOfUnsecuredSeniorNotes
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		      
Alabama Power [Member] | SEGCO [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Short-term Debt 42,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SegcoMember		      
Alabama Power [Member] | Senior notes due December 1, 2018 [Member] | SEGCO [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Guarantee of unsecured senior notes 100,000,000so_GuaranteeOfUnsecuredSeniorNotes
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_LongtermDebtTypeAxis
= so_MaturityDecemberFirstTwoThousandEighteenMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		      
Alabama Power [Member] | Natural Gas Pipeline [Member]        
Jointly owned utility plant interests        
Construction Work in Progress 15,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ dei_LegalEntityAxis
= so_AlabamaPowerMember
/ us-gaap_PublicUtilityAxis
= so_NaturalGasPipelineMember		      
Alabama Power [Member] | Plant Miller (coal) Units 1 and 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 91.84%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		 [1]      
Plant in Service 1,512,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Accumulated Depreciation 561,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Construction Work in Progress 14,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 1,320so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantMillerCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Alabama Power [Member] | SEGCO [Member]        
Jointly owned utility plant interests        
Percent Ownership 86.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_SegcoMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Alabama Power [Member] | Greene County [Member]        
Jointly owned utility plant interests        
Percent Ownership 60.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		 [2]      
Plant in Service 164,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Accumulated Depreciation 96,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Construction Work in Progress 1,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 500so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_AlabamaPowerMember		      
Georgia Power [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Short-term Debt 156,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		 1,047,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		    
Plant acquisition adjustment 28,000,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		 28,000,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		    
Georgia Power [Member] | SEGCO [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Share Of Purchased Power 84,000,000so_ShareOfPurchasedPower
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		 91,000,000so_ShareOfPurchasedPower
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		    
Georgia Power [Member] | Purchased Power from Affiliates [Member] | SEGCO [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Share Of Purchased Power     107,000,000so_ShareOfPurchasedPower
/ us-gaap_IncomeStatementLocationAxis
= so_PurchasedPowerFromAffiliatesMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_SouthernElectricGeneratingCompanyMember		  
Georgia Power [Member] | Alabama Power [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 1,020so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_AlabamaPowerMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Plant Vogtle (nuclear) Units 1 and 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 45.70%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 3,420,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 2,059,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 46,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantVogtleNuclearUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Plant Hatch (nuclear) [Member]        
Jointly owned utility plant interests        
Percent Ownership 50.10%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 1,117,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 559,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 66,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantHatchNuclearMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Plant Scherer (coal) Units 1 and 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 8.40%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 254,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 83,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 1,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererCoalUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Plant Wansley (coal) [Member]        
Jointly owned utility plant interests        
Percent Ownership 53.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 856,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 278,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 15,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantWansleyCoalMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Rocky Mountain (pumped storage) [Member]        
Jointly owned utility plant interests        
Percent Ownership 25.40%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 182,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 124,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 2,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_RockyMountainPumpedStorageMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Intercession City (combustion turbine) [Member]        
Jointly owned utility plant interests        
Percent Ownership 33.30%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 14,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 5,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 0us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_IntercessionCityCombustionTurbineMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Vogtle Units 3 and 4 [Member]        
Jointly owned utility plant interests        
Percent Ownership 45.70%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_VogtleUnitsThreeAndFourMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Georgia Power [Member] | Plant Scherer Unit 3 (coal) [Member]        
Jointly owned utility plant interests        
Percent Ownership 75.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Plant in Service 1,172,000,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Accumulated Depreciation 417,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Construction Work in Progress 10,000,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GeorgiaPowerMember		      
Gulf Power [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Short-term Debt 109,977,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_GulfPowerMember		 135,878,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_GulfPowerMember		    
Plant acquisition adjustment 1,776,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_GulfPowerMember		 2,031,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_GulfPowerMember		    
Gulf Power [Member] | Plant Scherer Unit 3 (coal) [Member]        
Jointly owned utility plant interests        
Percent Ownership 25.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Plant in Service 387,511,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		 [3]      
Accumulated Depreciation 130,069,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Construction Work in Progress 2,912,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 818so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Plant acquisition adjustment 1,800,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantSchererUnitThreeMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Gulf Power [Member] | Plant Daniel Units 1 &2 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 50.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Plant in Service 285,834,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Accumulated Depreciation 177,304,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Construction Work in Progress 286,343,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 1,000so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_GulfPowerMember		      
Mississippi Power [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Plant acquisition adjustment 81,412,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_MississippiPowerMember		 81,412,000us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAmountOfAcquisitionAdjustments1
/ dei_LegalEntityAxis
= so_MississippiPowerMember		    
Mississippi Power [Member] | Greene County [Member]        
Jointly owned utility plant interests        
Construction Work in Progress       5,600,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_PublicUtilityAxis
= so_GreeneCountyMember
Mississippi Power [Member] | Greene County [Member] | Alabama Power [Member]        
Jointly owned utility plant interests        
Percent Ownership 40.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_AlabamaPowerMember		      
Plant in Service 102,384,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_AlabamaPowerMember		      
Accumulated Depreciation 51,911,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_AlabamaPowerMember		      
Construction Work in Progress 902,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_AlabamaPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 500so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_GreeneCountyMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_AlabamaPowerMember		      
Mississippi Power [Member] | Plant Daniel Units 1 &2 2 [Member]        
Jointly owned utility plant interests        
Percent Ownership 50.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember		      
Mississippi Power [Member] | Plant Daniel Units 1 &2 2 [Member] | Gulf Power [Member]        
Jointly owned utility plant interests        
Percent Ownership 50.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_GulfPowerMember		      
Plant in Service 299,440,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_GulfPowerMember		      
Accumulated Depreciation 155,606,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_GulfPowerMember		      
Construction Work in Progress 286,240,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfConstructionWorkInProgress
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_GulfPowerMember		      
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 1,000so_ElectricGeneratingUnitsCapacity
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantDanielUnitsOneAndTwoMember
/ dei_LegalEntityAxis
= so_MississippiPowerMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= so_GulfPowerMember		      
Southern Power [Member]        
Joint Ownership Agreements (Textual) [Abstract]        
Total Megawatt Capacity 659so_ElectricGeneratingUnitsCapacity
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
Short-term Debt 194,917,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_SouthernPowerMember		 0us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= so_SouthernPowerMember		    
Southern Power [Member] | Plant Stanton (combined cycle) Unit A [Member]        
Jointly owned utility plant interests        
Plant in Service 156,500,000us-gaap_JointlyOwnedUtilityPlantGrossOwnershipAmountOfPlantInService
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
Accumulated Depreciation $ 46,600,000us-gaap_JointlyOwnedUtilityPlantOwnershipAmountOfPlantAccumulatedDepreciation
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
Southern Power [Member] | Plant Stanton (combined cycle) Unit A [Member] | Southern Power [Member]        
Jointly owned utility plant interests        
Percent Ownership 65.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember
/ so_JointlyOwnedUtilityPlantInterestsAxis
= so_SouthernPowerMember
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
Southern Power [Member] | Plant Stanton (combined cycle) Unit A [Member] | Orlando Utilities Commission [Member]        
Jointly owned utility plant interests        
Percent Ownership 28.00%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember
/ so_JointlyOwnedUtilityPlantInterestsAxis
= so_OrlandoUtilitiesCommissionMember
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
Southern Power [Member] | Plant Stanton (combined cycle) Unit A [Member] | Florida Municipal Power Agency [Member]        
Jointly owned utility plant interests        
Percent Ownership 3.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember
/ so_JointlyOwnedUtilityPlantInterestsAxis
= so_FloridaMunicipalPowerAgencyMember
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
Southern Power [Member] | Plant Stanton (combined cycle) Unit A [Member] | Kissimmee Utility Authority [Member]        
Jointly owned utility plant interests        
Percent Ownership 3.50%us-gaap_JointlyOwnedUtilityPlantProportionateOwnershipShare
/ us-gaap_JointlyOwnedUtilityPlantAxis
= so_PlantStantonCombinedCycleUnitMember
/ so_JointlyOwnedUtilityPlantInterestsAxis
= so_KissimmeeUtilityAuthorityMember
/ dei_LegalEntityAxis
= so_SouthernPowerMember		      
[1] Jointly owned with PowerSouth Energy Cooperative, Inc.
[2] Jointly owned with an affiliate, Mississippi Power.
[3] Includes net plant acquisition adjustment of $1.8 million.