Retirement Benefits - Amounts Not Yet Recognized in Net Periodic Postretirement Benefit Cost, AOCI and Regulatory Assets and Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	$ 4,032,000,000	$ 3,579,000,000
Pension Plans [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	107,000,000	135,000,000
Net (Gain) Loss	3,031,000,000	2,588,000,000
Other regulatory assets, deferred	3,013,000,000	2,614,000,000
Prior Service Cost, Estimated	27,000,000
Net (Gain) Loss, Estimated	200,000,000
Reclassification adjustments
Amortization of prior service costs	30,000,000	32,000,000	33,000,000
Net periodic benefit cost	135,000,000	19,000,000	54,000,000
Pension Plans [Member] | Accumulated Other Comprehensive Income [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	7,000,000	7,000,000
Net (Gain) Loss	118,000,000	102,000,000
Prior Service Cost, Estimated	1,000,000
Net (Gain) Loss, Estimated	8,000,000
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	109,000,000	68,000,000
Net (gain) loss	21,000,000	43,000,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of prior service costs	(1,000,000)	(1,000,000)
Amortization of net gain (loss)	(4,000,000)	(1,000,000)
Total reclassification adjustments	(5,000,000)	(2,000,000)
Net periodic benefit cost	16,000,000	41,000,000
Ending Balance	125,000,000	109,000,000
Pension Plans [Member] | Regulatory Assets [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	100,000,000	128,000,000
Net (Gain) Loss	2,913,000,000	2,486,000,000
Prior Service Cost, Estimated	26,000,000
Net (Gain) Loss, Estimated	192,000,000
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	2,614,000,000	1,749,000,000
Net (gain) loss	519,000,000	915,000,000
Change in prior service costs/transition obligation	0	1,000,000
Reclassification adjustments
Amortization of prior service costs	(29,000,000)	(31,000,000)
Amortization of net gain (loss)	(91,000,000)	(20,000,000)
Total reclassification adjustments	(120,000,000)	(51,000,000)
Net periodic benefit cost	399,000,000	865,000,000
Ending Balance	3,013,000,000	2,614,000,000
Other Postretirement Benefits [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	13,000,000	17,000,000
Net (Gain) Loss	349,000,000	320,000,000
Transition Obligation	(5,000,000)	(14,000,000)
Other regulatory assets, deferred	360,000,000	345,000,000
Prior Service Cost, Estimated	4,000,000
Net (Gain) Loss, Estimated	12,000,000
Transition Obligation, Estimated	5,000,000
Reclassification adjustments
Amortization of prior service costs	20,000,000	20,000,000	20,000,000
Net periodic benefit cost	66,000,000	69,000,000	82,000,000
Other Postretirement Benefits [Member] | Accumulated Other Comprehensive Income [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	0	0
Net (Gain) Loss	7,000,000	6,000,000
Transition Obligation	0	0
Prior Service Cost, Estimated	0
Net (Gain) Loss, Estimated	0
Transition Obligation, Estimated	0
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	6,000,000	3,000,000
Net (gain) loss	1,000,000	3,000,000
Change in prior service costs/transition obligation	0	0
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	1,000,000	3,000,000
Ending Balance	7,000,000	6,000,000
Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	13,000,000	17,000,000
Net (Gain) Loss	342,000,000	314,000,000
Transition Obligation	(5,000,000)	(14,000,000)
Prior Service Cost, Estimated	4,000,000
Net (Gain) Loss, Estimated	12,000,000
Transition Obligation, Estimated	5,000,000
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	345,000,000	292,000,000
Net (gain) loss	35,000,000	84,000,000
Change in prior service costs/transition obligation	0	(12,000,000)
Reclassification adjustments
Amortization of transition obligation	(10,000,000)	(10,000,000)
Amortization of prior service costs	(4,000,000)	(5,000,000)
Amortization of net gain (loss)	(6,000,000)	(4,000,000)
Total reclassification adjustments	(20,000,000)	(19,000,000)
Net periodic benefit cost	15,000,000	53,000,000
Ending Balance	360,000,000	345,000,000
Gulf Power [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	372,294,000	323,116,000
Reclassification adjustments
Amortization of prior service costs	1,262,000	1,262,000	1,302,000
Net periodic benefit cost	5,543,000	47,000	2,163,000
Gulf Power [Member] | Pension Plans [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	5,565,000	6,402,000
Net (Gain) Loss	133,696,000	109,451,000
Other regulatory assets, deferred	139,261,000	115,853,000
Prior Service Cost, Estimated	1,164,000
Net (Gain) Loss, Estimated	(8,385,000)
Gulf Power [Member] | Pension Plans [Member] | Regulatory Assets [Member]
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	115,853,000	75,096,000
Net (gain) loss	28,157,000	42,531,000
Change in prior service costs/transition obligation	426,000	0
Reclassification adjustments
Amortization of prior service costs	(1,262,000)	(1,262,000)
Amortization of net gain (loss)	(3,913,000)	(512,000)
Total reclassification adjustments	(5,175,000)	(1,774,000)
Net periodic benefit cost	23,408,000	40,757,000
Ending Balance	139,261,000	115,853,000
Gulf Power [Member] | Other Postretirement Benefits [Member]
Reclassification adjustments
Amortization of prior service costs	379,000	396,000	406,000
Net periodic benefit cost	3,602,000	3,741,000	4,350,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	324,000	510,000
Net (Gain) Loss	1,845,000	(464,000)
Transition Obligation	0	193,000
Other regulatory assets, deferred	2,169,000	239,000
Prior Service Cost, Estimated	186,000
Net (Gain) Loss, Estimated	0
Transition Obligation, Estimated	0
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	239,000	0
Net (gain) loss	2,309,000	635,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of transition obligation	(193,000)	(257,000)
Amortization of prior service costs	(186,000)	(186,000)
Amortization of net gain (loss)	0	47,000
Total reclassification adjustments	(379,000)	(396,000)
Net periodic benefit cost	1,930,000	239,000
Ending Balance	2,169,000	239,000
Gulf Power [Member] | Other Postretirement Benefits [Member] | Regulatory Liabilities [Member]
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	0	(166,000)
Net (gain) loss	0	166,000
Change in prior service costs/transition obligation	0	0
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	0	166,000
Ending Balance	0	0
Mississippi Power [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	236,225,000	185,694,000
Reclassification adjustments
Amortization of prior service costs	1,309,000	1,309,000	1,391,000
Net periodic benefit cost	8,723,000	3,922,000	6,790,000
Mississippi Power [Member] | Pension Plans [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	5,261,000	6,570,000
Net (Gain) Loss	141,577,000	110,784,000
Other regulatory assets, deferred	146,838,000	117,354,000
Prior Service Cost, Estimated	1,143,000
Net (Gain) Loss, Estimated	(9,461,000)
Mississippi Power [Member] | Pension Plans [Member] | Regulatory Assets [Member]
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	117,354,000	78,130,000
Net (gain) loss	34,893,000	41,647,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of prior service costs	(1,309,000)	(1,309,000)
Amortization of net gain (loss)	(4,100,000)	(1,114,000)
Total reclassification adjustments	(5,409,000)	(2,423,000)
Net periodic benefit cost	29,484,000	39,224,000
Ending Balance	146,838,000	117,354,000
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	(2,498,000)	(2,686,000)
Net (Gain) Loss	17,952,000	15,839,000
Transition Obligation	0	171,000
Other regulatory assets, deferred	15,454,000	13,324,000
Prior Service Cost, Estimated	(188,000)
Net (Gain) Loss, Estimated	(659,000)
Transition Obligation, Estimated	0
Reclassification adjustments
Amortization of prior service costs	470,000	274,000	574,000
Net periodic benefit cost	4,111,000	3,815,000	4,816,000
Mississippi Power [Member] | Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	13,324,000	8,618,000
Net (gain) loss	2,600,000	4,980,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of transition obligation	(171,000)	(228,000)
Amortization of prior service costs	188,000	188,000
Amortization of net gain (loss)	(487,000)	(234,000)
Total reclassification adjustments	(470,000)	(274,000)
Net periodic benefit cost	2,130,000	4,706,000
Ending Balance	15,454,000	13,324,000
Georgia Power [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	1,798,000,000	1,604,000,000
Georgia Power [Member] | Pension Plans [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	37,000,000	48,000,000
Net (Gain) Loss	1,095,000,000	947,000,000
Other regulatory assets, deferred	1,132,000,000	995,000,000
Prior Service Cost, Estimated	10,000,000
Net (Gain) Loss, Estimated	(74,000,000)
Reclassification adjustments
Amortization of prior service costs	12,000,000	12,000,000	13,000,000
Net periodic benefit cost	25,000,000	(15,000,000)	(6,000,000)
Georgia Power [Member] | Pension Plans [Member] | Regulatory Assets [Member]
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	995,000,000	689,000,000
Net (gain) loss	182,000,000	324,000,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of prior service costs	(12,000,000)	(12,000,000)
Amortization of net gain (loss)	(33,000,000)	(6,000,000)
Total reclassification adjustments	(45,000,000)	(18,000,000)
Net periodic benefit cost	137,000,000	306,000,000
Ending Balance	1,132,000,000	995,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	(4,000,000)	(4,000,000)
Net (Gain) Loss	186,000,000	179,000,000
Transition Obligation	5,000,000	11,000,000
Other regulatory assets, deferred	187,000,000	186,000,000
Prior Service Cost, Estimated	0
Net (Gain) Loss, Estimated	(7,000,000)
Transition Obligation, Estimated	4,000,000
Reclassification adjustments
Amortization of prior service costs	10,000,000	11,000,000	10,000,000
Net periodic benefit cost	25,000,000	29,000,000	33,000,000
Georgia Power [Member] | Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	186,000,000	179,000,000
Net (gain) loss	11,000,000	29,000,000
Change in prior service costs/transition obligation	0	(12,000,000)
Reclassification adjustments
Amortization of transition obligation	(6,000,000)	(6,000,000)
Amortization of prior service costs	0	(1,000,000)
Amortization of net gain (loss)	(4,000,000)	(3,000,000)
Total reclassification adjustments	(10,000,000)	(10,000,000)
Net periodic benefit cost	1,000,000	7,000,000
Ending Balance	187,000,000	186,000,000
Alabama Power [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	1,083,000,000	994,000,000
Alabama Power [Member] | Pension Plans [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	822,000,000	727,000,000
Reclassification adjustments
Amortization of prior service costs	7,000,000	9,000,000	9,000,000
Net periodic benefit cost	6,000,000	(21,000,000)	(19,000,000)
Alabama Power [Member] | Pension Plans [Member] | Regulatory Assets [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	26,000,000	33,000,000
Net (Gain) Loss	796,000,000	694,000,000
Prior Service Cost, Estimated	7,000,000
Net (Gain) Loss, Estimated	(52,000,000)
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	727,000,000	497,000,000
Net (gain) loss	125,000,000	243,000,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of prior service costs	(7,000,000)	(9,000,000)
Amortization of net gain (loss)	(23,000,000)	(4,000,000)
Total reclassification adjustments	(30,000,000)	(13,000,000)
Net periodic benefit cost	95,000,000	230,000,000
Ending Balance	822,000,000	727,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Other regulatory assets, deferred	89,000,000	96,000,000
Reclassification adjustments
Amortization of prior service costs	6,000,000	7,000,000	7,000,000
Net periodic benefit cost	10,000,000	11,000,000	14,000,000
Alabama Power [Member] | Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Amounts included in accumulated other Comprehensive income and regulatory assets related to the other postretirement benefit plans
Prior Service Cost	22,000,000	26,000,000
Net (Gain) Loss	67,000,000	68,000,000
Transition Obligation	0	2,000,000
Other regulatory assets, deferred	89,000,000	96,000,000
Prior Service Cost, Estimated	4,000,000
Net (Gain) Loss, Estimated	(2,000,000)
Transition Obligation, Estimated	0
Changes in the balance of regulatory assets and liabilities [Roll Forward]
Beginning Balance	96,000,000	72,000,000
Net (gain) loss	(1,000,000)	31,000,000
Change in prior service costs/transition obligation	0	0
Reclassification adjustments
Amortization of transition obligation	(2,000,000)	(3,000,000)
Amortization of prior service costs	(4,000,000)	(4,000,000)
Amortization of net gain (loss)	0	0
Total reclassification adjustments	(6,000,000)	(7,000,000)
Net periodic benefit cost	(7,000,000)	24,000,000
Ending Balance	$ 89,000,000	$ 96,000,000