Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Pension Plans [Member]
Pension Plans and Postretirement Plans
Service cost	$ 50	$ 46
Interest cost	98	98
Expected return on plan assets	(145)	(152)
Net amortization	31	13
Net cost (income)	34	5
Pension Plans [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	11	11
Interest cost	23	24
Expected return on plan assets	(40)	(43)
Net amortization	8	3
Net cost (income)	2	(5)
Pension Plans [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	15	14
Interest cost	35	36
Expected return on plan assets	(55)	(59)
Net amortization	11	5
Net cost (income)	6	(4)
Pension Plans [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	2
Interest cost	4	4
Expected return on plan assets	(6)	(7)
Net amortization	1	1
Net cost (income)	1
Pension Plans [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	2
Interest cost	5	4
Expected return on plan assets	(6)	(6)
Net amortization	1	1
Net cost (income)	2	1
Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Service cost	5	5
Interest cost	21	23
Expected return on plan assets	(15)	(16)
Net amortization	5	5
Net cost (income)	16	17
Other Postretirement Benefits [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	1	1
Interest cost	5	6
Expected return on plan assets	(6)	(6)
Net amortization	2	2
Net cost (income)	2	3
Other Postretirement Benefits [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	1	2
Interest cost	9	10
Expected return on plan assets	(7)	(8)
Net amortization	3	3
Net cost (income)	6	7
Other Postretirement Benefits [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Interest cost	1	1
Net cost (income)	1	1
Other Postretirement Benefits [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Interest cost	1	1
Net cost (income)	$ 1	$ 1