Derivatives - Balance Sheet Offsetting (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Southern Company [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 15		$ 21
Derivative Liability, Fair Value, Gross Liability	271		225
Southern Company [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	1		4
Derivative Liability, Fair Value, Amount Offset Against Collateral	219		192
Southern Company [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7	[1]	13	[1]
Derivative Liability, Fair Value, Gross Liability	225	[1]	201	[1]
Southern Company [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(6)	[2]	(9)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(6)	[2]	(9)	[2]
Southern Company [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	6		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	44		16
Southern Company [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	8	[1]	8	[1]
Derivative Liability, Fair Value, Gross Liability	46	[1]	24	[1]
Southern Company [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(2)	[2]	(8)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(2)	[2]	(8)	[2]
Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1		1
Derivative Liability, Fair Value, Gross Liability	73		61
Alabama Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		1
Derivative Liability, Fair Value, Amount Offset Against Collateral	58		53
Alabama Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	[1]	1	[1]
Derivative Liability, Fair Value, Gross Liability	59	[1]	53	[1]
Alabama Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(1)	[2]	0	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(1)	[2]	0	[2]
Alabama Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	14		8
Alabama Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	0	[1]
Derivative Liability, Fair Value, Gross Liability	14	[1]	8	[1]
Alabama Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [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]
Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	12		13
Derivative Liability, Fair Value, Gross Liability	55		41
Georgia Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	18		20
Georgia Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	6	[1]	7	[1]
Derivative Liability, Fair Value, Gross Liability	24	[1]	27	[1]
Georgia Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(6)	[2]	(7)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(6)	[2]	(7)	[2]
Georgia Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	4		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	29		8
Georgia Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	6	[1]	6	[1]
Derivative Liability, Fair Value, Gross Liability	31	[1]	14	[1]
Georgia Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(2)	[2]	(6)	[2]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(2)	[2]	(6)	[2]
Gulf Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	90		72
Gulf Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	90		72
Gulf Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	0	[1]
Derivative Liability, Fair Value, Gross Liability	90	[1]	72	[1]
Gulf Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [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]
Gulf Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0		0
Gulf Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	0	[1]
Derivative Liability, Fair Value, Gross Liability	0	[1]	0	[1]
Gulf Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [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]
Mississippi Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Derivative Liability, Fair Value, Gross Liability	52		45
Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	52		45
Mississippi Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	0	[1]
Derivative Liability, Fair Value, Gross Liability	52	[1]	45	[1]
Mississippi Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [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]
Mississippi Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0		0
Mississippi Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	0	[1]
Derivative Liability, Fair Value, Gross Liability	0	[1]	0	[1]
Mississippi Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [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]
Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		5
Derivative Liability, Fair Value, Gross Liability	0		4
Southern Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		5
Derivative Liability, Fair Value, Amount Offset Against Collateral	0		4
Southern Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	5	[1]
Derivative Liability, Fair Value, Gross Liability	0	[1]	4	[1]
Southern Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [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]
Southern Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0		0
Derivative Liability, Fair Value, Amount Offset Against Collateral	0		0
Southern Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[1]	0	[1]
Derivative Liability, Fair Value, Gross Liability	0	[1]	0	[1]
Southern Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [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 offsets 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.