Retirement Benefits - Components of Accumulated OCI and Changes in Regulatory Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Reclassification adjustments
Amortization of prior service costs	$ 27,000	$ 30,000	$ 32,000
Net periodic benefit cost	245,000	135,000	19,000
Pension Plans, Defined Benefit [Member] | Accumulated Other Comprehensive Income (Loss)
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	125,000	109,000
Net (gain) loss	(52,000)	21,000
Change in prior service costs	0
Reclassification adjustments
Amortization of prior service costs	(1,000)	(1,000)
Amortization of net gain (loss)	(8,000)	(4,000)
Total reclassification adjustments	(9,000)	(5,000)
Net periodic benefit cost	(61,000)	16,000
Ending Balance	64,000	125,000
Pension Plans, Defined Benefit [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	3,013,000	2,614,000
Net (gain) loss	(1,145,000)	519,000
Change in prior service costs	1,000
Reclassification adjustments
Amortization of prior service costs	(26,000)	(29,000)
Amortization of net gain (loss)	(192,000)	(91,000)
Total reclassification adjustments	(218,000)	(120,000)
Net periodic benefit cost	(1,362,000)	399,000
Ending Balance	1,651,000	3,013,000
Other Postretirement Benefits [Member]
Reclassification adjustments
Amortization of prior service costs	21,000	20,000	20,000
Net periodic benefit cost	63,000	66,000	69,000
Other Postretirement Benefits [Member] | Accumulated Other Comprehensive Income (Loss)
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	7,000	6,000
Net (gain) loss	(6,000)	1,000
Reclassification adjustments
Amortization of transition obligation	0	0
Amortization of prior service costs	0	0
Amortization of net gain (loss)	0	0
Total reclassification adjustments	0	0
Net periodic benefit cost	(6,000)	1,000
Ending Balance	1,000	7,000
Other Postretirement Benefits [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	360,000	345,000
Net (gain) loss	(266,000)	35,000
Reclassification adjustments
Amortization of transition obligation	(5,000)	(10,000)
Amortization of prior service costs	(4,000)	(4,000)
Amortization of net gain (loss)	(12,000)	(6,000)
Total reclassification adjustments	(21,000)	(20,000)
Net periodic benefit cost	(287,000)	15,000
Ending Balance	73,000	360,000
Alabama Power [Member] | Pension Plans, Defined Benefit [Member]
Reclassification adjustments
Amortization of prior service costs	7,000	7,000	9,000
Net periodic benefit cost	47,000	6,000	(21,000)
Alabama Power [Member] | Pension Plans, Defined Benefit [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	822,000	727,000
Net (gain) loss	(287,000)	125,000
Reclassification adjustments
Amortization of prior service costs	(7,000)	(7,000)
Amortization of net gain (loss)	(52,000)	(23,000)
Total reclassification adjustments	(59,000)	(30,000)
Net periodic benefit cost	(346,000)	95,000
Ending Balance	476,000	822,000
Alabama Power [Member] | Other Postretirement Benefits [Member]
Reclassification adjustments
Amortization of prior service costs	5,000	6,000	7,000
Net periodic benefit cost	7,000	10,000	11,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	89,000	96,000
Net (gain) loss	(99,000)	(1,000)
Reclassification adjustments
Amortization of transition obligation	0	(2,000)
Amortization of prior service costs	(3,000)	(4,000)
Amortization of net gain (loss)	(2,000)	0
Total reclassification adjustments	(5,000)	(6,000)
Net periodic benefit cost	(104,000)	(7,000)
Ending Balance	(15,000)	89,000
Georgia Power [Member] | Pension Plans, Defined Benefit [Member]
Reclassification adjustments
Amortization of prior service costs	10,000	12,000	12,000
Net periodic benefit cost	79,000	25,000	(15,000)
Georgia Power [Member] | Pension Plans, Defined Benefit [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	1,132,000	995,000
Net (gain) loss	(438,000)	182,000
Reclassification adjustments
Amortization of prior service costs	(10,000)	(12,000)
Amortization of net gain (loss)	(74,000)	(33,000)
Total reclassification adjustments	(84,000)	(45,000)
Net periodic benefit cost	(522,000)	137,000
Ending Balance	610,000	1,132,000
Georgia Power [Member] | Other Postretirement Benefits [Member]
Reclassification adjustments
Amortization of prior service costs	12,000	10,000	11,000
Net periodic benefit cost	26,000	25,000	29,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	187,000	186,000
Net (gain) loss	(106,000)	11,000
Reclassification adjustments
Amortization of transition obligation	(4,000)	(6,000)
Amortization of prior service costs	0	0
Amortization of net gain (loss)	(8,000)	(4,000)
Total reclassification adjustments	(12,000)	(10,000)
Net periodic benefit cost	(118,000)	1,000
Ending Balance	69,000	187,000
Gulf Power [Member]
Reclassification adjustments
Amortization of prior service costs	1,164	1,262	1,262
Net periodic benefit cost	11,563	5,543	47
Gulf Power [Member] | Pension Plans, Defined Benefit [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	139,261	115,853
Net (gain) loss	(54,432)	28,157
Change in prior service costs	0	426
Reclassification adjustments
Amortization of prior service costs	(1,164)	(1,262)
Amortization of net gain (loss)	(8,385)	(3,913)
Total reclassification adjustments	(9,549)	(5,175)
Net periodic benefit cost	(63,981)	23,408
Ending Balance	75,280	139,261
Gulf Power [Member] | Other Postretirement Benefits [Member]
Reclassification adjustments
Amortization of prior service costs	186	379	396
Net periodic benefit cost	3,285	3,602	3,741
Gulf Power [Member] | Other Postretirement Benefits [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	2,169	239
Net (gain) loss	(8,967)	2,309
Reclassification adjustments
Amortization of transition obligation	0	(193)
Amortization of prior service costs	(186)	(186)
Amortization of net gain (loss)	0	0
Total reclassification adjustments	(186)	(379)
Net periodic benefit cost	(9,153)	1,930
Ending Balance	(6,984)	2,169
Mississippi Power [Member]
Reclassification adjustments
Amortization of prior service costs	1,143	1,309	1,309
Net periodic benefit cost	12,884	8,723	3,922
Mississippi Power [Member] | Pension Plans, Defined Benefit [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	146,838	117,354
Net (gain) loss	(58,662)	34,893
Reclassification adjustments
Amortization of prior service costs	(1,143)	(1,309)
Amortization of net gain (loss)	(9,461)	(4,100)
Total reclassification adjustments	(10,604)	(5,409)
Net periodic benefit cost	(69,266)	29,484
Ending Balance	77,572	146,838
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Reclassification adjustments
Amortization of prior service costs	471	470	274
Net periodic benefit cost	3,769	4,111	3,815
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Net Regulatory Assets/Liabilities [Member]
Changes in the Balance of AOCI and Regulatory Assets [Roll Forward]
Beginning Balance	15,454	13,324
Net (gain) loss	(12,867)	2,600
Reclassification adjustments
Amortization of transition obligation	0	(171)
Amortization of prior service costs	188	188
Amortization of net gain (loss)	(659)	(487)
Total reclassification adjustments	(471)	(470)
Net periodic benefit cost	(13,338)	2,130
Ending Balance	$ 2,116	$ 15,454