Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans [Member]
Pension Plans and Postretirement Plans
Service cost	$ 58	$ 50
Interest cost	97	98
Expected return on plan assets	(151)	(145)
Amortization:
Prior service costs	7	7
Net (gain)/loss	(50)	(24)
Net cost	61	34
Pension Plans [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	13	11
Interest cost	23	23
Expected return on plan assets	(39)	(40)
Amortization:
Prior service costs	2	2
Net (gain)/loss	(13)	(6)
Net cost	12	2
Pension Plans [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	17	15
Interest cost	34	35
Expected return on plan assets	(53)	(55)
Amortization:
Prior service costs	3	3
Net (gain)/loss	(19)	(8)
Net cost	20	6
Pension Plans [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	3	2
Interest cost	4	4
Expected return on plan assets	(6)	(6)
Amortization:
Prior service costs	0	0
Net (gain)/loss	(2)	(1)
Net cost	3	1
Pension Plans [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	3	2
Interest cost	5	5
Expected return on plan assets	(7)	(6)
Amortization:
Prior service costs	0	0
Net (gain)/loss	(2)	(1)
Net cost	3	2
Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Service cost	6	5
Interest cost	19	21
Expected return on plan assets	(14)	(15)
Amortization:
Transition obligation	1	2
Prior service costs	1	1
Net (gain)/loss	(3)	(2)
Net cost	16	16
Other Postretirement Benefits [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	1
Interest cost	5	5
Expected return on plan assets	(6)	(6)
Amortization:
Transition obligation	0	1
Prior service costs	1	1
Net (gain)/loss	0	0
Net cost	2	2
Other Postretirement Benefits [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	1
Interest cost	8	9
Expected return on plan assets	(6)	(7)
Amortization:
Transition obligation	1	2
Prior service costs	0	0
Net (gain)/loss	(2)	(1)
Net cost	7	6
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:
Transition obligation	0	0
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:
Transition obligation	0	0
Prior service costs	0	0
Net (gain)/loss	0	0
Net cost	$ 1	$ 1