Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plans [Member] | Southern Company [Member]
Pension Plans and Postretirement Plans
Service cost	$ 62	$ 64
Interest cost	100	111
Expected return on plan assets	(187)	(181)
Amortization:
Prior service costs	4	6
Net (gain)/loss	38	54
Net cost	17	54
Pension Plans [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	14	15
Interest cost	24	26
Expected return on plan assets	(46)	(45)
Amortization:
Prior service costs	1	2
Net (gain)/loss	10	14
Net cost	3	12
Pension Plans [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	17	18
Interest cost	34	38
Expected return on plan assets	(64)	(63)
Amortization:
Prior service costs	1	3
Net (gain)/loss	14	19
Net cost	2	15
Pension Plans [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	3	3
Interest cost	5	5
Expected return on plan assets	(9)	(8)
Amortization:
Prior service costs	0	0
Net (gain)/loss	2	3
Net cost	1	3
Pension Plans [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	3	3
Interest cost	5	5
Expected return on plan assets	(9)	(8)
Amortization:
Prior service costs	0	0
Net (gain)/loss	2	3
Net cost	1	3
Other Postretirement Benefits [Member] | Southern Company [Member]
Pension Plans and Postretirement Plans
Service cost	5	6
Interest cost	18	19
Expected return on plan assets	(14)	(15)
Amortization:
Prior service costs	2	1
Net (gain)/loss	3	5
Net cost	14	16
Other Postretirement Benefits [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	1	1
Interest cost	5	5
Expected return on plan assets	(6)	(6)
Amortization:
Prior service costs	1	1
Net (gain)/loss	0	0
Net cost	1	1
Other Postretirement Benefits [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	2
Interest cost	8	8
Expected return on plan assets	(6)	(6)
Amortization:
Prior service costs	0	0
Net (gain)/loss	2	3
Net cost	6	7
Other Postretirement Benefits [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization:
Prior service costs	0	0
Net (gain)/loss	0	0
Net cost	1	1
Other Postretirement Benefits [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	0	0
Interest cost	1	1
Expected return on plan assets	0	0
Amortization:
Prior service costs	0	0
Net (gain)/loss	0	0
Net cost	$ 1	$ 1