Retirement Benefits - Postretirement Benefit Plans, Net Periodic 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, Defined Benefit [Member]
Components of the other postretirement benefit plans net periodic cost
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)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	95,000	21,000	10,000
Net amortization	30,000	32,000	33,000
Net periodic benefit cost	135,000	19,000	54,000
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	(376,000)
Benefit Payments for 2014	(397,000)
Benefit Payments for 2015	(419,000)
Benefit Payments for 2016	(440,000)
Benefit Payments for 2017	(465,000)
Benefit Payments for 2018 to 2022	(2,632,000)
Other Postretirement Benefits [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	21,000	21,000	25,000
Interest cost	85,000	92,000	100,000
Expected return on plan assets	(60,000)	(64,000)	(63,000)
Net amortization	20,000	20,000	20,000
Net periodic benefit cost	66,000	69,000	82,000
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	110,000
Benefit Payments for 2014	116,000
Benefit Payments for 2015	122,000
Benefit Payments for 2016	127,000
Benefit Payments for 2017	130,000
Benefit Payments for 2018 to 2022	661,000
Subsidy Receipts for 2013	(11,000)
Subsidy Receipts for 2014	(12,000)
Subsidy Receipts for 2015	(13,000)
Subsidy Receipts for 2016	(14,000)
Subsidy Receipts for 2017	(16,000)
Subsidy Receipts for 2018 to 2022	(88,000)
Total for 2013	99,000
Total for 2014	104,000
Total for 2015	109,000
Total for 2016	113,000
Total for 2017	114,000
Total for 2018 to 2022	573,000
Gulf Power [Member]
Components of the other postretirement benefit plans net periodic cost
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)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	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, Defined Benefit [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	9,101	8,431
Interest cost	17,199	17,074
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	(15,767)
Benefit Payments for 2014	(16,606)
Benefit Payments for 2015	(17,427)
Benefit Payments for 2016	(18,272)
Benefit Payments for 2017	(19,383)
Benefit Payments for 2018 to 2022	(113,108)
Gulf Power [Member] | Other Postretirement Benefits [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	1,167	1,132	1,304
Interest cost	3,367	3,658	4,121
Expected return on plan assets	(1,311)	(1,445)	(1,481)
Net amortization	379	396	406
Net periodic benefit cost	3,602	3,741	4,350
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	4,473
Benefit Payments for 2014	4,707
Benefit Payments for 2015	4,903
Benefit Payments for 2016	5,117
Benefit Payments for 2017	5,211
Benefit Payments for 2018 to 2022	26,913
Subsidy Receipts for 2013	(488)
Subsidy Receipts for 2014	(537)
Subsidy Receipts for 2015	(589)
Subsidy Receipts for 2016	(643)
Subsidy Receipts for 2017	(705)
Subsidy Receipts for 2018 to 2022	(3,804)
Total for 2013	3,985
Total for 2014	4,170
Total for 2015	4,314
Total for 2016	4,474
Total for 2017	4,506
Total for 2018 to 2022	23,109
Mississippi Power [Member]
Components of the other postretirement benefit plans net periodic cost
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)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	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, Defined Benefit [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	9,416	8,838
Interest cost	18,019	17,827
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	(16,282)
Benefit Payments for 2014	(17,121)
Benefit Payments for 2015	(17,947)
Benefit Payments for 2016	(18,886)
Benefit Payments for 2017	(20,001)
Benefit Payments for 2018 to 2022	(117,471)
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	1,038	1,012	1,305
Interest cost	4,155	4,292	4,763
Expected return on plan assets	(1,552)	(1,763)	(1,826)
Net amortization	470	274	574
Net periodic benefit cost	4,111	3,815	4,816
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	5,174
Benefit Payments for 2014	5,442
Benefit Payments for 2015	5,754
Benefit Payments for 2016	5,995
Benefit Payments for 2017	6,280
Benefit Payments for 2018 to 2022	33,822
Subsidy Receipts for 2013	(601)
Subsidy Receipts for 2014	(663)
Subsidy Receipts for 2015	(720)
Subsidy Receipts for 2016	(782)
Subsidy Receipts for 2017	(845)
Subsidy Receipts for 2018 to 2022	(4,414)
Total for 2013	4,573
Total for 2014	4,779
Total for 2015	5,034
Total for 2016	5,213
Total for 2017	5,435
Total for 2018 to 2022	29,408
Georgia Power [Member] | Pension Plans, Defined Benefit [Member]
Components of the other postretirement benefit plans net periodic cost
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)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	33,000	6,000	2,000
Net amortization	12,000	12,000	13,000
Net periodic benefit cost	25,000	(15,000)	(6,000)
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	(148,000)
Benefit Payments for 2014	(154,000)
Benefit Payments for 2015	(160,000)
Benefit Payments for 2016	(166,000)
Benefit Payments for 2017	(173,000)
Benefit Payments for 2018 to 2022	(952,000)
Georgia Power [Member] | Other Postretirement Benefits [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	7,000	7,000	9,000
Interest cost	37,000	41,000	44,000
Expected return on plan assets	(29,000)	(30,000)	(30,000)
Net amortization	10,000	11,000	10,000
Net periodic benefit cost	25,000	29,000	33,000
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	49,000
Benefit Payments for 2014	51,000
Benefit Payments for 2015	53,000
Benefit Payments for 2016	55,000
Benefit Payments for 2017	56,000
Benefit Payments for 2018 to 2022	282,000
Subsidy Receipts for 2013	(5,000)
Subsidy Receipts for 2014	(5,000)
Subsidy Receipts for 2015	(5,000)
Subsidy Receipts for 2016	(6,000)
Subsidy Receipts for 2017	(7,000)
Subsidy Receipts for 2018 to 2022	(36,000)
Total for 2013	44,000
Total for 2014	46,000
Total for 2015	48,000
Total for 2016	49,000
Total for 2017	49,000
Total for 2018 to 2022	246,000
Alabama Power [Member] | Pension Plans, Defined Benefit [Member]
Components of the other postretirement benefit plans net periodic cost
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)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements and Curtailments	23,000	4,000	2,000
Net amortization	7,000	9,000	9,000
Net periodic benefit cost	6,000	(21,000)	(19,000)
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	(99,000)
Benefit Payments for 2014	(104,000)
Benefit Payments for 2015	(108,000)
Benefit Payments for 2016	(112,000)
Benefit Payments for 2017	(117,000)
Benefit Payments for 2018 to 2022	(637,000)
Alabama Power [Member] | Other Postretirement Benefits [Member]
Components of the other postretirement benefit plans net periodic cost
Service cost	5,000	5,000	6,000
Interest cost	22,000	24,000	26,000
Expected return on plan assets	(23,000)	(25,000)	(25,000)
Net amortization	6,000	7,000	7,000
Net periodic benefit cost	10,000	11,000	14,000
Summary of estimation of future benefit payments and subsidy receipts based on assumptions used to measure the accumulated benefit obligation for postretirement plans
Benefit Payments for 2013	30,000
Benefit Payments for 2014	32,000
Benefit Payments for 2015	33,000
Benefit Payments for 2016	34,000
Benefit Payments for 2017	35,000
Benefit Payments for 2018 to 2022	176,000
Subsidy Receipts for 2013	(3,000)
Subsidy Receipts for 2014	(4,000)
Subsidy Receipts for 2015	(4,000)
Subsidy Receipts for 2016	(4,000)
Subsidy Receipts for 2017	(5,000)
Subsidy Receipts for 2018 to 2022	(26,000)
Total for 2013	27,000
Total for 2014	28,000
Total for 2015	29,000
Total for 2016	30,000
Total for 2017	30,000
Total for 2018 to 2022	$ 150,000