Derivatives - Balance Sheet Offsetting (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Southern Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 13		$ 27
Derivative Liability, Fair Value, Gross Liability	56		56
Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	5		7
Derivative Liability, Fair Value, Gross Liability	12		8
Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		5
Derivative Liability, Fair Value, Gross Liability	12		21
Gulf Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	3		7
Derivative Liability, Fair Value, Gross Liability	19		17
Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2		5
Derivative Liability, Fair Value, Gross Liability	10		10
Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		1
Derivative Liability, Fair Value, Gross Liability	0		1
Energy Related Derivative [Member] | Southern Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	1		2
Derivative Liability, Fair Value, Amount Offset Against Collateral	42		34
Energy Related Derivative [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	1		2
Derivative Liability, Fair Value, Amount Offset Against Collateral	7		3
Energy Related Derivative [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	11		16
Energy Related Derivative [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		1
Derivative Liability, Fair Value, Amount Offset Against Collateral	16		11
Energy Related Derivative [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		1
Derivative Liability, Fair Value, Amount Offset Against Collateral	8		6
Energy Related Derivative [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	1		1
Derivative Liability, Fair Value, Amount Offset Against Collateral	1		1
Energy Related Derivative [Member] | Net Amount Of Derivatives [Member] | Southern Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	12	[1]	24	[1]
Derivative Liability, Fair Value, Gross Liability	53	[1]	56	[1]
Energy Related Derivative [Member] | Net Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	5	[1]	7	[1]
Derivative Liability, Fair Value, Gross Liability	11	[1]	8	[1]
Energy Related Derivative [Member] | Net Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	[1]	5	[1]
Derivative Liability, Fair Value, Gross Liability	12	[1]	21	[1]
Energy Related Derivative [Member] | Net Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	3	[1]	7	[1]
Derivative Liability, Fair Value, Gross Liability	19	[1]	17	[1]
Energy Related Derivative [Member] | Net Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	[1]	5	[1]
Derivative Liability, Fair Value, Gross Liability	10	[1]	10	[1]
Energy Related Derivative [Member] | Net Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	[1]	1	[1]
Derivative Liability, Fair Value, Gross Liability	1	[1]	1	[1]
Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member] | Southern Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(11)	[2]	(22)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(11)	[2]	(22)	[2]
Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(4)	[2]	(5)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(4)	[2]	(5)	[2]
Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(1)	[2]	(5)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(1)	[2]	(5)	[2]
Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member] | Gulf Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(3)	[2]	(6)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(3)	[2]	(6)	[2]
Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member] | Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(2)	[2]	(4)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(2)	[2]	(4)	[2]
Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	0	[2]	0	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 0	[2]	$ 0	[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.