Derivatives - Balance Sheet Presentation (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			$ 6	[1]
Southern Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	15		21
Derivative Liability, Fair Value, Gross Liability	271		225
Southern Company [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			4
Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Derivative Liability, Fair Value, Gross Liability	73		61
Alabama Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			0	[1]
Alabama Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			0
Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	12		13
Derivative Liability, Fair Value, Gross Liability	55		41
Georgia Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			0	[1]
Georgia Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			0
Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	90		72
Gulf Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			0	[1]
Gulf Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			0
Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	52		45
Mississippi Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			0	[1]
Mississippi Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			0
Southern Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		5
Derivative Liability, Fair Value, Gross Liability	0		4
Southern Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset			5	[1]
Southern Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability			4
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	8		8
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	46		24
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	7		7
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	45		17
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	1		7
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	14		8
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	14		8
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6		6
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	31		14
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	5		5
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	31		9
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		5
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	7		7
Derivative Liability, Fair Value, Gross Liability	225		197
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6		7
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		0
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	117	[2]	118	[2]
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	108		79
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Derivative Liability, Fair Value, Gross Liability	59		53
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	33	[2]	32	[2]
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	26		21
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6		7
Derivative Liability, Fair Value, Gross Liability	24		27
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	5		6
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	21	[2]	23	[2]
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	3		4
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	90		72
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	37	[2]	37	[2]
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	53		35
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	52		45
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy Related Derivative [Member] | Other deferred charges and assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	26	[2]	26	[2]
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy Related Derivative [Member] | Other deferred credits and liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 26		$ 19

[1] Southern Power includes current assets related to derivatives not designated as hedging instruments in "Assets from risk management activities."

[2] Georgia Power and Gulf Power include current liabilities related to derivatives designated as hedging instruments in "Liabilities from risk management activities."