Derivatives - Balance Sheet Presentation (Details) - USD ($) $ in Millions	Jun. 30, 2015		Dec. 31, 2014
Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			$ 6
Southern Company [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	$ 16		21
Energy-related derivatives	194		225
Southern Company [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			4
Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	2		1
Energy-related derivatives	55		61
Alabama Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Alabama Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	8		13
Energy-related derivatives	21		41
Georgia Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Georgia Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	0		0
Energy-related derivatives	74		72
Gulf Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Gulf Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	0		0
Energy-related derivatives	41		45
Mississippi Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Mississippi Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Southern Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	0		5
Energy-related derivatives	0		4
Southern Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			5
Southern Power [Member] | Not Designated as Hedging Instrument [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			4
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			7
Energy-related derivatives	180		197
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	5		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]
Energy-related derivatives			0
Hedging Instruments for Regulatory Purposes [Member] | Southern Company [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	99	[1]	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]
Energy-related derivatives	81		79
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			1
Energy-related derivatives	48		53
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	2		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]
Energy-related derivatives			0
Hedging Instruments for Regulatory Purposes [Member] | Alabama Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	31	[1]	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]
Energy-related derivatives	17		21
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			7
Energy-related derivatives	17		27
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	3		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]
Energy-related derivatives			1
Hedging Instruments for Regulatory Purposes [Member] | Georgia Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	15	[1]	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]
Energy-related derivatives	2		4
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Energy-related derivatives	74		72
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives			0
Hedging Instruments for Regulatory Purposes [Member] | Gulf Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	32	[1]	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]
Energy-related derivatives	42		35
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Energy-related derivatives	41		45
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy Related Derivative [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives			0
Hedging Instruments for Regulatory Purposes [Member] | Mississippi Power [Member] | Energy Related Derivative [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	21	[1]	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]
Energy-related derivatives	20		19
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			8
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	14		24
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	11		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]
Energy-related derivatives			1
Cash Flow and Fair Value Hedging [Member] | Southern Company [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	8	[1]	17	[2]
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]
Energy-related derivatives	6		7
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	7		8
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Alabama Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	7	[1]	8	[2]
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]
Energy-related derivatives	0		0
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			6
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	4		14
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member] | Other current assets [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives			1
Cash Flow and Fair Value Hedging [Member] | Georgia Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	1	[1]	9	[2]
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]
Energy-related derivatives	3		5
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives	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]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Gulf Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	0	[1]	0	[2]
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]
Energy-related derivatives	0		0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives	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]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Mississippi Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	0	[1]	0	[2]
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]
Energy-related derivatives	0		0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	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]
Energy-related derivatives	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]
Energy-related derivatives			0
Cash Flow and Fair Value Hedging [Member] | Southern Power [Member] | Interest Rate Contract [Member] | Other current liabilities [Member]
Derivatives, Fair Value [Line Items]
Energy-related derivatives	0	[1]	0	[2]
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]
Energy-related derivatives	$ 0		$ 0

[1] Gulf Power includes current liabilities related to derivatives designated as hedging instruments in "Liabilities from risk management activities."

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