Derivatives - Balance Sheet Offsetting (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Southern Company [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	$ 63	$ 29
Derivatives presented in the Balance Sheet, liabilities	155	250
Southern Company [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Net derivative assets	4	1
Net interest rate derivative liabilities	78	214
Southern Company [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	36	7
Derivatives presented in the Balance Sheet, liabilities	110	220
Southern Company [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(32)	(6)
Gross amounts not offset in the Balance Sheet, liabilities	(32)	(6)
Southern Company [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net derivative assets	9
Net interest rate derivative liabilities	27
Southern Company [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	27
Derivatives presented in the Balance Sheet, liabilities	45
Southern Company [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(18)
Gross amounts not offset in the Balance Sheet, liabilities	(18)
Alabama Power [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	10	1
Derivatives presented in the Balance Sheet, liabilities	22	70
Alabama Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Net derivative assets	2	0
Net interest rate derivative liabilities	14	54
Alabama Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	10	1
Derivatives presented in the Balance Sheet, liabilities	22	55
Alabama Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(8)	(1)
Gross amounts not offset in the Balance Sheet, liabilities	(8)	(1)
Alabama Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net derivative assets	0
Net interest rate derivative liabilities	0
Alabama Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	0
Derivatives presented in the Balance Sheet, liabilities	0
Alabama Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	0
Gross amounts not offset in the Balance Sheet, liabilities	0
Georgia Power [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	29	7
Derivatives presented in the Balance Sheet, liabilities	5	21
Georgia Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Net derivative assets	11	0
Net interest rate derivative liabilities	1	13
Georgia Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	15	2
Derivatives presented in the Balance Sheet, liabilities	5	15
Georgia Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(4)	(2)
Gross amounts not offset in the Balance Sheet, liabilities	(4)	(2)
Georgia Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net derivative assets	14
Net interest rate derivative liabilities	0
Georgia Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	14
Derivatives presented in the Balance Sheet, liabilities	0
Georgia Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	0
Gross amounts not offset in the Balance Sheet, liabilities	0
Gulf Power [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	2	1
Derivatives presented in the Balance Sheet, liabilities	62	100
Gulf Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Net derivative assets	0	0
Net interest rate derivative liabilities	53	100
Gulf Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	2	0
Derivatives presented in the Balance Sheet, liabilities	55	100
Gulf Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(2)	0
Gross amounts not offset in the Balance Sheet, liabilities	(2)	0
Gulf Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net derivative assets	0
Net interest rate derivative liabilities	7
Gulf Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	0
Derivatives presented in the Balance Sheet, liabilities	7
Gulf Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	0
Gross amounts not offset in the Balance Sheet, liabilities	0
Mississippi Power [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	1	0
Derivatives presented in the Balance Sheet, liabilities	23	47
Mississippi Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Net derivative assets	0	0
Net interest rate derivative liabilities	22	47
Mississippi Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	1	0
Derivatives presented in the Balance Sheet, liabilities	23	47
Mississippi Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(1)	0
Gross amounts not offset in the Balance Sheet, liabilities	(1)	0
Mississippi Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net derivative assets	0
Net interest rate derivative liabilities	0
Mississippi Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	0
Derivatives presented in the Balance Sheet, liabilities	0
Mississippi Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	0
Gross amounts not offset in the Balance Sheet, liabilities	0
Southern Power [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	8	7
Derivatives presented in the Balance Sheet, liabilities	43	3
Southern Power [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Net derivative assets	5	3
Net interest rate derivative liabilities	2	2
Southern Power [Member] | Energy Related Derivative [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	8	4
Derivatives presented in the Balance Sheet, liabilities	5	3
Southern Power [Member] | Energy Related Derivative [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	(3)	(1)
Gross amounts not offset in the Balance Sheet, liabilities	(3)	$ (1)
Southern Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Net derivative assets	0
Net interest rate derivative liabilities	38
Southern Power [Member] | Interest Rate Contract [Member] | Net Amount Of Derivatives [Member]
Derivative [Line Items]
Derivatives presented in the Balance Sheet, assets	0
Derivatives presented in the Balance Sheet, liabilities	38
Southern Power [Member] | Interest Rate Contract [Member] | Gross Amount Of Derivatives [Member]
Derivative [Line Items]
Gross amounts not offset in the Balance Sheet, assets	0
Gross amounts not offset in the Balance Sheet, liabilities	$ 0