Derivatives - Balance Sheet Offsetting (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Energy-related derivatives [Member]
Derivative [Line Items]
Offsetting Derivative Asset	$ 11		$ 3
Energy-related derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	7		1
Energy-related derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	0		0
Energy-related derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	4		0
Energy-related derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	1		1
Energy-related derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	4		2
Energy-related derivatives [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Offsetting Derivative Asset	50	[1]	26	[1]
Energy-related derivatives [Member] | Net Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	12	[1]	5	[1]
Energy-related derivatives [Member] | Net Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	13	[1]	11	[1]
Energy-related derivatives [Member] | Net Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	14	[1]	4	[1]
Energy-related derivatives [Member] | Net Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	6	[1]	3	[1]
Energy-related derivatives [Member] | Net Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	5	[1]	3	[1]
Energy-related derivatives [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Offsetting Derivative Asset	(39)	[2]	(23)	[2]
Energy-related derivatives [Member] | Gross Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	(5)	[2]	(4)	[2]
Energy-related derivatives [Member] | Gross Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	(13)	[2]	(11)	[2]
Energy-related derivatives [Member] | Gross Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	(10)	[2]	(4)	[2]
Energy-related derivatives [Member] | Gross Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	(5)	[2]	(2)	[2]
Energy-related derivatives [Member] | Gross Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	(1)	[2]	(1)	[2]
Interest Rate Contract [Member]
Derivative [Line Items]
Offsetting Derivative Asset	24		88
Interest Rate Contract [Member] | Alabama Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	2		14
Interest Rate Contract [Member] | Georgia Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	15		34
Interest Rate Contract [Member] | Gulf Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	6		23
Interest Rate Contract [Member] | Mississippi Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	6		17
Interest Rate Contract [Member] | Southern Power [Member]
Derivative [Line Items]
Offsetting Derivative Asset	0		1
Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Offsetting Derivative Liability	63	[1]	111	[1]
Interest Rate Contract [Member] | Net Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	7	[1]	18	[1]
Interest Rate Contract [Member] | Net Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	28	[1]	45	[1]
Interest Rate Contract [Member] | Net Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	16	[1]	27	[1]
Interest Rate Contract [Member] | Net Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	11	[1]	19	[1]
Interest Rate Contract [Member] | Net Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	1	[1]	2	[1]
Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Offsetting Derivative Liability	(39)	[2]	(23)	[2]
Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	(5)	[2]	(4)	[2]
Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	(13)	[2]	(11)	[2]
Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	(10)	[2]	(4)	[2]
Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	(5)	[2]	(2)	[2]
Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Offsetting Derivative Liability	$ (1)	[2]	$ (1)	[2]

[1] None of the registrants offset fair value amounts for multiple derivative instruments executed with the same counterparty on the balance sheets; therefore, gross and net amounts of derivative assets and liabilities presented on the balance sheets are the same.

[2] Includes gross amounts subject to netting terms that are not offset on the balance sheets and any cash/financial collateral pledged or received.