Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Pension Plans [Member]
Pension Plans and Postretirement Plans
Service cost	$ 49	$ 46	$ 148	$ 138
Interest cost	98	97	295	292
Expected return on plan assets	(145)	(152)	(436)	(456)
Net amortization	32	14	94	40
Net cost (income)	34	5	101	14
Pension Plans [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	11	11	33	32
Interest cost	23	24	70	72
Expected return on plan assets	(40)	(44)	(121)	(130)
Net amortization	8	3	23	10
Net cost (income)	2	(6)	5	(16)
Pension Plans [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	15	14	45	43
Interest cost	35	36	106	108
Expected return on plan assets	(56)	(59)	(166)	(176)
Net amortization	12	5	34	14
Net cost (income)	6	(4)	19	(11)
Pension Plans [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	2	7	6
Interest cost	5	4	13	13
Expected return on plan assets	(7)	(6)	(20)	(20)
Net amortization	1	0	4	1
Net cost (income)	1	0	4	0
Pension Plans [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	3	7	7
Interest cost	5	4	14	13
Expected return on plan assets	(6)	(7)	(18)	(19)
Net amortization	2	1	4	2
Net cost (income)	3	1	7	3
Other Postretirement Benefits [Member]
Pension Plans and Postretirement Plans
Service cost	5	6	16	16
Interest cost	21	23	63	69
Expected return on plan assets	(15)	(16)	(45)	(48)
Net amortization	5	5	15	15
Net cost (income)	16	18	49	52
Other Postretirement Benefits [Member] | Alabama Power [Member]
Pension Plans and Postretirement Plans
Service cost	1	1	4	4
Interest cost	6	6	17	18
Expected return on plan assets	(6)	(6)	(18)	(19)
Net amortization	1	2	4	5
Net cost (income)	2	3	7	8
Other Postretirement Benefits [Member] | Georgia Power [Member]
Pension Plans and Postretirement Plans
Service cost	2	1	5	5
Interest cost	8	11	27	31
Expected return on plan assets	(7)	(8)	(21)	(23)
Net amortization	3	3	8	8
Net cost (income)	6	7	19	21
Other Postretirement Benefits [Member] | Gulf Power [Member]
Pension Plans and Postretirement Plans
Service cost	0	0	1	1
Interest cost	1	1	3	3
Expected return on plan assets	0	0	(1)	(1)
Net amortization	0	0	0	0
Net cost (income)	1	1	3	3
Other Postretirement Benefits [Member] | Mississippi Power [Member]
Pension Plans and Postretirement Plans
Service cost	0	0	1	1
Interest cost	1	1	3	3
Expected return on plan assets	0	0	(1)	(1)
Net amortization	0	0	0	0
Net cost (income)	$ 1	$ 1	$ 3	$ 3