Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Plans [Member] | Southern Company [Member]
Pension Plans and Postretirement Plans
Service cost	$ 65	$ 53	$ 193	$ 160
Interest cost	111	109	333	326
Expected return on plan assets	(181)	(161)	(543)	(484)
Amortization:
Prior service costs	6	6	19	19
Net (gain)/loss	53	28	161	83
Net cost	54	35	163	104
Pension Plans [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	14	12	44	36
Interest cost	26	26	79	78
Expected return on plan assets	(44)	(42)	(133)	(126)
Amortization:
Prior service costs	2	2	5	5
Net (gain)/loss	14	7	41	23
Net cost	12	5	36	16
Pension Plans [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	18	16	54	47
Interest cost	38	39	115	115
Expected return on plan assets	(62)	(57)	(188)	(170)
Amortization:
Prior service costs	2	2	7	7
Net (gain)/loss	19	10	57	30
Net cost	15	10	45	29
Pension Plans [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	3	4	9	8
Interest cost	5	4	15	14
Expected return on plan assets	(8)	(7)	(24)	(21)
Amortization:
Prior service costs	1	0	1	1
Net (gain)/loss	2	1	7	3
Net cost	3	2	8	5
Pension Plans [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	3	3	9	8
Interest cost	5	5	16	15
Expected return on plan assets	(8)	(8)	(25)	(22)
Amortization:
Prior service costs	0	0	1	1
Net (gain)/loss	3	2	8	4
Net cost	3	2	9	6
Other Postretirement Benefits [Member] | Southern Company [Member]
Pension Plans and Postretirement Plans
Service cost	6	5	17	16
Interest cost	20	19	59	59
Expected return on plan assets	(15)	(14)	(44)	(44)
Amortization:
Prior service costs	1	1	3	3
Net (gain)/loss	4	1	13	2
Net cost	16	12	48	36
Other Postretirement Benefits [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	1	1	4	4
Interest cost	5	5	15	15
Expected return on plan assets	(6)	(6)	(19)	(19)
Amortization:
Prior service costs	2	1	3	3
Net (gain)/loss	0	0	1	0
Net cost	2	1	4	3
Other Postretirement Benefits [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	2	5	5
Interest cost	9	9	26	26
Expected return on plan assets	(6)	(6)	(18)	(19)
Amortization:
Prior service costs	0	0	0	0
Net (gain)/loss	2	0	8	1
Net cost	7	5	21	13
Other Postretirement Benefits [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	1	0	1	1
Interest cost	0	0	2	2
Expected return on plan assets	0	0	(1)	(1)
Amortization:
Prior service costs	0	0	0	0
Net (gain)/loss	0	0	0	0
Net cost	1	0	2	2
Other Postretirement Benefits [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	0	0	1	1
Interest cost	1	0	3	2
Expected return on plan assets	0	0	(1)	(1)
Amortization:
Prior service costs	0	0	0	0
Net (gain)/loss	0	0	0	0
Net cost	$ 1	$ 0	$ 3	$ 2