Derivatives - Balance Sheet Presentation (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	$ 60	$ 36
Derivative Liability, Fair Value	63	111
Hedging Instruments for Regulatory Purposes [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	45	23
Derivative Liability, Fair Value	62	109
Cash Flow and Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	10	10
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	5	3
Derivative Liability, Fair Value		2
Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	36	74
Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	26	35
Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	25	10
Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	20	13
Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	1	1
Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value		1
Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	2	2
Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Assets from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	3	1
Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	7	7
Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	3	3
Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	12	5
Derivative Liability, Fair Value	7	18
Alabama Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	12	5
Derivative Liability, Fair Value	7	18
Alabama Power [Member] | Cash Flow and Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Alabama Power [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Derivative Liability, Fair Value		0
Alabama Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	5	14
Alabama Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	2	4
Alabama Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	7	2
Alabama Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	5	3
Alabama Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	0	0
Alabama Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value		0
Alabama Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Alabama Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Assets from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Alabama Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Alabama Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	13	11
Derivative Liability, Fair Value	28	45
Georgia Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	13	11
Derivative Liability, Fair Value	28	45
Georgia Power [Member] | Cash Flow and Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Georgia Power [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Derivative Liability, Fair Value		0
Georgia Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	17	30
Georgia Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	11	15
Georgia Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	6	6
Georgia Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	7	5
Georgia Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	0	0
Georgia Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value		0
Georgia Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Georgia Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Assets from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Georgia Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Georgia Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	14	4
Derivative Liability, Fair Value	16	27
Gulf Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	14	4
Derivative Liability, Fair Value	16	27
Gulf Power [Member] | Cash Flow and Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Gulf Power [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Derivative Liability, Fair Value		0
Gulf Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	8	17
Gulf Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	8	10
Gulf Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	9	1
Gulf Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	5	3
Gulf Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	0	0
Gulf Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value		0
Gulf Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Gulf Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Assets from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Gulf Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Gulf Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	6	3
Derivative Liability, Fair Value	11	19
Mississippi Power [Member] | Hedging Instruments for Regulatory Purposes [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	6	3
Derivative Liability, Fair Value	11	19
Mississippi Power [Member] | Cash Flow and Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Mississippi Power [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Derivative Liability, Fair Value		0
Mississippi Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	6	13
Mississippi Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	5	6
Mississippi Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	3	1
Mississippi Power [Member] | Energy-related derivatives [Member] | Hedging Instruments for Regulatory Purposes [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	3	2
Mississippi Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	0	0
Mississippi Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value		0
Mississippi Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Mississippi Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Assets from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Mississippi Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Mississippi Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Southern Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	5	3
Derivative Liability, Fair Value	1	2
Southern Power [Member] | Cash Flow and Fair Value Hedging [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Southern Power [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	5	3
Derivative Liability, Fair Value		2
Southern Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Liabilities from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	1	1
Southern Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value		1
Southern Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	2	2
Southern Power [Member] | Energy-related derivatives [Member] | Not Designated as Hedging Instrument [Member] | Assets from risk management activities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	3	1
Southern Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0	0
Southern Power [Member] | Interest Rate Contract [Member] | Cash Flow and Fair Value Hedging [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	$ 0	$ 0