Retirement Benefits - Components of Net Periodic Benefit Cost and Estimated Future Benefit Payments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plans [Member]
Components of net periodic
Service cost	$ 198,000	$ 184,000	$ 172,000
Interest cost	393,000	389,000	391,000
Expected return on plan assets	(581,000)	(607,000)	(552,000)
Recognized net loss	95,000	21,000	10,000
Net amortization	30,000	32,000	33,000
Net periodic benefit cost	135,000	19,000	54,000
Estimated pension benefit payments
2013	376,000
2014	397,000
2015	419,000
2016	440,000
2017	465,000
2018 to 2022	2,632,000
Gulf Power [Member]
Components of net periodic
Service cost	9,101	8,431	7,853
Interest cost	17,199	17,074	17,305
Expected return on plan assets	(25,932)	(27,232)	(24,695)
Recognized net loss	3,913	512	398
Net amortization	1,262	1,262	1,302
Net periodic benefit cost	5,543	47	2,163
Gulf Power [Member] | Pension Plans [Member]
Components of net periodic
Service cost	9,101	8,431
Interest cost	17,199	17,074
Estimated pension benefit payments
2013	15,767
2014	16,606
2015	17,427
2016	18,272
2017	19,383
2018 to 2022	113,108
Mississippi Power [Member]
Components of net periodic
Service cost	9,416	8,838	8,300
Interest cost	18,019	17,827	17,916
Expected return on plan assets	(24,121)	(25,166)	(21,451)
Recognized net loss	4,100	1,114	634
Net amortization	1,309	1,309	1,391
Net periodic benefit cost	8,723	3,922	6,790
Mississippi Power [Member] | Pension Plans [Member]
Components of net periodic
Service cost	9,416	8,838
Interest cost	18,019	17,827
Estimated pension benefit payments
2013	16,282
2014	17,121
2015	17,947
2016	18,886
2017	20,001
2018 to 2022	117,471
Georgia Power [Member] | Pension Plans [Member]
Components of net periodic
Service cost	60,000	57,000	54,000
Interest cost	141,000	144,000	145,000
Expected return on plan assets	(221,000)	(234,000)	(220,000)
Recognized net loss	33,000	6,000	2,000
Net amortization	12,000	12,000	13,000
Net periodic benefit cost	25,000	(15,000)	(6,000)
Estimated pension benefit payments
2013	148,000
2014	154,000
2015	160,000
2016	166,000
2017	173,000
2018 to 2022	952,000
Alabama Power [Member] | Pension Plans [Member]
Components of net periodic
Service cost	44,000	43,000	41,000
Interest cost	94,000	96,000	97,000
Expected return on plan assets	(162,000)	(173,000)	(168,000)
Recognized net loss	23,000	4,000	2,000
Net amortization	7,000	9,000	9,000
Net periodic benefit cost	6,000	(21,000)	(19,000)
Estimated pension benefit payments
2013	99,000
2014	104,000
2015	108,000
2016	112,000
2017	117,000
2018 to 2022	$ 637,000