Derivatives - Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 29	$ 21
Derivative Liability, Fair Value, Gross Liability	250	225
Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Liability, Fair Value, Gross Liability	70	61
Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7	5
Derivative Liability, Fair Value, Gross Liability	3	4
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	214	192
Energy Related Derivative [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	1
Derivative Liability, Fair Value, Amount Offset Against Collateral	54	53
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	13	20
Energy Related Derivative [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	3	5
Derivative Liability, Fair Value, Amount Offset Against Collateral	2	4
Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	13	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	21	16
Interest Rate Contract [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral	1	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	2	8
Net Amount Of Derivatives [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	7	13
Derivative Liability, Fair Value, Gross Liability	220	201
Net Amount Of Derivatives [Member] | Energy Related Derivative [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	1	1
Derivative Liability, Fair Value, Gross Liability	55	53
Net Amount Of Derivatives [Member] | Energy Related Derivative [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	2	7
Derivative Liability, Fair Value, Gross Liability	15	27
Net Amount Of Derivatives [Member] | Energy Related Derivative [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	4	5
Derivative Liability, Fair Value, Gross Liability	3	4
Net Amount Of Derivatives [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	22	8
Derivative Liability, Fair Value, Gross Liability	30	24
Net Amount Of Derivatives [Member] | Interest Rate Contract [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	5	6
Derivative Liability, Fair Value, Gross Liability	6	14
Gross Amount Of Derivatives [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(6)	(9)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(6)	(9)
Gross Amount Of Derivatives [Member] | Energy Related Derivative [Member] | Alabama Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(1)	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(1)	0
Gross Amount Of Derivatives [Member] | Energy Related Derivative [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(2)	(7)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(2)	(7)
Gross Amount Of Derivatives [Member] | Energy Related Derivative [Member] | Southern Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(1)	0
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(1)	0
Gross Amount Of Derivatives [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(9)	(8)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(9)	(8)
Gross Amount Of Derivatives [Member] | Interest Rate Contract [Member] | Georgia Power [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	(4)	(6)
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (4)	$ (6)