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Segment and Related Information - Financial Data for Business Segments and Products and Services (Details) (USD $)
 3 Months Ended 12 Months Ended 24 Months Ended
Dec. 31, 2014
entities
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
entities
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Segment Reporting Information [Line Items]                        
Number of traditional operating companies 4so_NumberOfTraditionalOperatingCompanies               4so_NumberOfTraditionalOperatingCompanies     4so_NumberOfTraditionalOperatingCompanies
Revenues $ 4,017,000,000us-gaap_Revenues $ 5,339,000,000us-gaap_Revenues $ 4,467,000,000us-gaap_Revenues $ 4,644,000,000us-gaap_Revenues $ 3,927,000,000us-gaap_Revenues $ 5,017,000,000us-gaap_Revenues $ 4,246,000,000us-gaap_Revenues $ 3,897,000,000us-gaap_Revenues $ 18,467,000,000us-gaap_Revenues $ 17,087,000,000us-gaap_Revenues $ 16,537,000,000us-gaap_Revenues  
Financial data for business segments                        
Operating revenues 4,017,000,000us-gaap_Revenues 5,339,000,000us-gaap_Revenues 4,467,000,000us-gaap_Revenues 4,644,000,000us-gaap_Revenues 3,927,000,000us-gaap_Revenues 5,017,000,000us-gaap_Revenues 4,246,000,000us-gaap_Revenues 3,897,000,000us-gaap_Revenues 18,467,000,000us-gaap_Revenues 17,087,000,000us-gaap_Revenues 16,537,000,000us-gaap_Revenues  
Depreciation and amortization                 1,945,000,000so_DepreciationAndAmortizationExcludingNuclearFuel 1,901,000,000so_DepreciationAndAmortizationExcludingNuclearFuel 1,787,000,000so_DepreciationAndAmortizationExcludingNuclearFuel  
Interest income                 19,000,000us-gaap_InvestmentIncomeInterestAndDividend 19,000,000us-gaap_InvestmentIncomeInterestAndDividend 40,000,000us-gaap_InvestmentIncomeInterestAndDividend  
Interest expense                 835,000,000us-gaap_InterestAndDebtExpense 824,000,000us-gaap_InterestAndDebtExpense 859,000,000us-gaap_InterestAndDebtExpense  
Income taxes                 977,000,000us-gaap_IncomeTaxExpenseBenefit 849,000,000us-gaap_IncomeTaxExpenseBenefit 1,334,000,000us-gaap_IncomeTaxExpenseBenefit  
Segment net income (loss) 283,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 718,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 611,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 351,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 414,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 852,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 297,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 81,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic 1,963,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic [1],[2] 1,644,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic [1],[2] 2,350,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic [1]  
Total assets 70,923,000,000us-gaap_Assets       64,546,000,000us-gaap_Assets       70,923,000,000us-gaap_Assets 64,546,000,000us-gaap_Assets 63,149,000,000us-gaap_Assets 70,923,000,000us-gaap_Assets
Gross property additions                 6,522,000,000us-gaap_PaymentsToAcquireProductiveAssets 5,868,000,000us-gaap_PaymentsToAcquireProductiveAssets 5,059,000,000us-gaap_PaymentsToAcquireProductiveAssets  
Kemper IGCC [Member]                        
Segment and Related Information (Textual) [Abstract]                        
Pre-Tax Charge To Income 70,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 418,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		   380,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 40,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 150,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 450,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 540,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 868,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 1,200,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		   2,050,000,000so_PreTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember
After Tax Charge To Income 43,200,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 258,100,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		   234,700,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 24,700,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 92,600,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 277,900,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 333,500,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 536,000,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		 729,000,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember		   1,260,000,000so_AfterTaxChargeToIncome
/ us-gaap_PublicUtilityAxis
= so_KemperIgccMember
Electric Utilities [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 18,406,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 17,035,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 16,478,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Financial data for business segments                        
Operating revenues                 18,406,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 17,035,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 16,478,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Depreciation and amortization                 1,929,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 1,886,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 1,772,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Interest income                 18,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 18,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 22,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Interest expense                 794,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 788,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 820,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Income taxes                 1,053,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 935,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 1,400,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Segment net income (loss)                 1,969,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 [1],[2] 1,652,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 [1],[2] 2,321,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 [1]  
Total assets 70,063,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		       63,775,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		       70,063,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 63,775,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 62,251,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 70,063,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
Gross property additions                 6,510,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 5,859,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		 5,054,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember		  
Traditional Operating Companies [Member] | Electric Utilities [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 17,354,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 16,136,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 15,730,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Financial data for business segments                        
Operating revenues                 17,354,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 16,136,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 15,730,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Depreciation and amortization                 1,709,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 1,711,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 1,629,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Interest income                 17,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 17,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 21,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Interest expense                 705,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 714,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 757,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Income taxes                 1,056,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 889,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 1,307,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Segment net income (loss)                 1,797,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 [1],[2] 1,486,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 [1],[2] 2,145,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 [1]  
Total assets 64,644,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		       59,447,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		       64,644,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 59,447,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 58,600,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 64,644,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember
Gross property additions                 5,568,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 5,226,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		 4,813,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_TraditionalOperatingCompaniesMember		  
Southern Power [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 383,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 346,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 425,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Financial data for business segments                        
Operating revenues                 383,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 346,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 425,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Southern Power [Member] | Electric Utilities [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 1,501,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 1,275,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 1,186,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Financial data for business segments                        
Operating revenues                 1,501,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 1,275,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 1,186,000,000us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Depreciation and amortization                 220,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 175,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 143,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Interest income                 1,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 1,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 1,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Interest expense                 89,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 74,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 63,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Income taxes                 (3,000,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 46,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 93,000,000us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
Segment net income (loss)                 172,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 [1],[2] 166,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 [1],[2] 175,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 [1]  
Total assets 5,550,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		       4,429,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		       5,550,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 4,429,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 3,780,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 5,550,000,000us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember
Gross property additions                 942,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 633,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		 241,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= so_SouthernPowerMember		  
All Other [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 159,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 139,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 141,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Financial data for business segments                        
Operating revenues                 159,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 139,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 141,000,000us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Depreciation and amortization                 16,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 15,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 15,000,000so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Interest income                 3,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 2,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 19,000,000us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Interest expense                 43,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 36,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 39,000,000us-gaap_InterestAndDebtExpense
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Income taxes                 (76,000,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 (85,000,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 (66,000,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Segment net income (loss)                 (3,000,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 [1],[2] (10,000,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 [1],[2] 33,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 [1]  
Total assets 1,156,000,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		       1,077,000,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		       1,156,000,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 1,077,000,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 1,116,000,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 1,156,000,000us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember
Gross property additions                 11,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 9,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		 5,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_AllOtherSegmentsMember		  
Eliminations [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 (98,000,000)us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (87,000,000)us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (82,000,000)us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Financial data for business segments                        
Operating revenues                 (98,000,000)us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (87,000,000)us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (82,000,000)us-gaap_Revenues
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Depreciation and amortization                 0so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Interest income                 (2,000,000)us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (1,000,000)us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (1,000,000)us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Interest expense                 (2,000,000)us-gaap_InterestAndDebtExpense
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_InterestAndDebtExpense
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_InterestAndDebtExpense
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Income taxes                 0us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (1,000,000)us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Segment net income (loss)                 (3,000,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 [1],[2] 2,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 [1],[2] (4,000,000)us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 [1]  
Total assets (296,000,000)us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		       (306,000,000)us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		       (296,000,000)us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (306,000,000)us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (218,000,000)us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (296,000,000)us-gaap_Assets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember
Gross property additions                 1,000,000us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Eliminations [Member] | Electric Utilities [Member]                        
Segment Reporting Information [Line Items]                        
Revenues                 (449,000,000)us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (376,000,000)us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (438,000,000)us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Financial data for business segments                        
Operating revenues                 (449,000,000)us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (376,000,000)us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (438,000,000)us-gaap_Revenues
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Depreciation and amortization                 0so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0so_DepreciationAndAmortizationExcludingNuclearFuel
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Interest income                 0us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_InvestmentIncomeInterestAndDividend
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Interest expense                 0us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_InterestAndDebtExpense
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Income taxes                 0us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 0us-gaap_IncomeTaxExpenseBenefit
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
Segment net income (loss)                 0us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 [1],[2] 0us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 [1],[2] 1,000,000us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 [1]  
Total assets (131,000,000)us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		       (101,000,000)us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		       (131,000,000)us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (101,000,000)us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (129,000,000)us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 (131,000,000)us-gaap_Assets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember
Gross property additions                 $ 0us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 $ 0us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		 $ 0us-gaap_PaymentsToAcquireProductiveAssets
/ us-gaap_ProductOrServiceAxis
= so_ElectricUtilitiesMember
/ us-gaap_StatementBusinessSegmentsAxis
= us-gaap_IntersegmentEliminationMember		  
[1] After dividends on preferred and preference stock of subsidiaries.
[2] Segment net income (loss) for the traditional operating companies in 2014 and 2013 includes $868 million in pre-tax charges ($536 million after tax) and $1.2 billion in pre-tax charges ($729 million after tax), respectively, for estimated probable losses on the Kemper IGCC. See Note 3 under "Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate" for additional information.