Derivatives - Balance Sheet Offsetting (Details) (Energy Related Derivative [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Derivative [Line Items]
Derivative Asset	$ 1		$ 3
Derivative Liability	74		88
Alabama Power [Member]
Derivative [Line Items]
Derivative Asset	0		1
Derivative Liability	12		14
Georgia Power [Member]
Derivative [Line Items]
Derivative Asset	0		0
Derivative Liability	27		34
Gulf Power [Member]
Derivative [Line Items]
Derivative Asset	0		0
Derivative Liability	22		23
Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset	0		1
Derivative Liability	13		17
Southern Power [Member]
Derivative [Line Items]
Derivative Asset	1		2
Derivative Liability	0		1
Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset	11	[1]	26	[1]
Derivative Liability	84	[1]	111	[1]
Net Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset	3	[1]	5	[1]
Derivative Liability	15	[1]	18	[1]
Net Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset	2	[1]	11	[1]
Derivative Liability	29	[1]	45	[1]
Net Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Asset	3	[1]	4	[1]
Derivative Liability	25	[1]	27	[1]
Net Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset	1	[1]	3	[1]
Derivative Liability	14	[1]	19	[1]
Net Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset	2	[1]	3	[1]
Derivative Liability	1	[1]	2	[1]
Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset	(10)	[2]	(23)	[2]
Derivative Liability	(10)	[2]	(23)	[2]
Gross Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset	(3)	[2]	(4)	[2]
Derivative Liability	(3)	[2]	(4)	[2]
Gross Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset	(2)	[2]	(11)	[2]
Derivative Liability	(2)	[2]	(11)	[2]
Gross Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Asset	(3)	[2]	(4)	[2]
Derivative Liability	(3)	[2]	(4)	[2]
Gross Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset	(1)	[2]	(2)	[2]
Derivative Liability	(1)	[2]	(2)	[2]
Gross Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset	(1)	[2]	(1)	[2]
Derivative Liability	$ (1)	[2]	$ (1)	[2]

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