Retirement Benefits - Amounts Recognized in Balance Sheets and Amounts in AOCI (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	$ 4,032,000,000	$ 3,579,000,000
Current liabilities, other	(483,000,000)	(426,000,000)
Employee benefit obligations	(2,540,000,000)	(2,442,000,000)
Accumulated OCI	(123,000,000)	(111,000,000)
Pension Plans [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	3,013,000,000	2,614,000,000
Current liabilities, other	(37,000,000)	(34,000,000)
Employee benefit obligations	(1,312,000,000)	(1,245,000,000)
Accumulated OCI	125,000,000	109,000,000
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	107,000,000	135,000,000
Net (Gain) Loss	3,031,000,000	2,588,000,000
Prior Service Cost, Estimated	27,000,000
Net (Gain) Loss, Estimated	200,000,000
Pension Plans [Member] | Accumulated Other Comprehensive Income [Member]
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
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
Pension Plans [Member] | Regulatory Assets [Member]
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
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
Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	360,000,000	345,000,000
Current liabilities, other	(3,000,000)	(4,000,000)
Employee benefit obligations	(1,048,000,000)	(1,018,000,000)
Accumulated OCI	7,000,000	6,000,000
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	13,000,000	17,000,000
Net (Gain) Loss	349,000,000	320,000,000
Prior Service Cost, Estimated	4,000,000
Net (Gain) Loss, Estimated	12,000,000
Other Postretirement Benefits [Member] | Accumulated Other Comprehensive Income [Member]
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	0	0
Net (Gain) Loss	7,000,000	6,000,000
Prior Service Cost, Estimated	0
Net (Gain) Loss, Estimated	0
Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	13,000,000	17,000,000
Net (Gain) Loss	342,000,000	314,000,000
Prior Service Cost, Estimated	4,000,000
Net (Gain) Loss, Estimated	12,000,000
Gulf Power [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	372,294,000	323,116,000
Current liabilities, other	(19,930,000)	(22,916,000)
Employee benefit obligations	(126,871,000)	(109,740,000)
Accumulated OCI	(1,581,000)	(2,154,000)
Gulf Power [Member] | Pension Plans [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	139,261,000	115,853,000
Current liabilities, other	(855,000)	(794,000)
Employee benefit obligations	(62,386,000)	(47,716,000)
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	5,565,000	6,402,000
Net (Gain) Loss	133,696,000	109,451,000
Prior Service Cost, Estimated	1,164,000
Net (Gain) Loss, Estimated	(8,385,000)
Gulf Power [Member] | Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Current liabilities, other	(661,000)	(624,000)
Employee benefit obligations	(58,507,000)	(55,321,000)
Gulf Power [Member] | Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	2,169,000	239,000
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	324,000	510,000
Net (Gain) Loss	1,845,000	(464,000)
Prior Service Cost, Estimated	186,000
Net (Gain) Loss, Estimated	0
Mississippi Power [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	236,225,000	185,694,000
Current liabilities, other	(18,766,000)	(17,533,000)
Employee benefit obligations	(157,421,000)	(161,065,000)
Accumulated OCI	(8,713,000)	(8,897,000)
Mississippi Power [Member] | Pension Plans [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	146,838,000	117,354,000
Current liabilities, other	(2,087,000)	(1,652,000)
Employee benefit obligations	(78,717,000)	(85,928,000)
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	5,261,000	6,570,000
Net (Gain) Loss	141,577,000	110,784,000
Prior Service Cost, Estimated	1,143,000
Net (Gain) Loss, Estimated	(9,461,000)
Mississippi Power [Member] | Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	15,454,000	13,324,000
Employee benefit obligations	(69,793,000)	(66,913,000)
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	(2,498,000)	(2,686,000)
Net (Gain) Loss	17,952,000	15,839,000
Prior Service Cost, Estimated	(188,000)
Net (Gain) Loss, Estimated	(659,000)
Georgia Power [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	1,798,000,000	1,604,000,000
Current liabilities, other	(137,000,000)	(139,000,000)
Employee benefit obligations	(950,000,000)	(905,000,000)
Accumulated OCI	(7,000,000)	(9,000,000)
Georgia Power [Member] | Pension Plans [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	1,132,000,000	995,000,000
Current liabilities, other	(11,000,000)	(10,000,000)
Employee benefit obligations	(474,000,000)	(324,000,000)
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	37,000,000	48,000,000
Net (Gain) Loss	1,095,000,000	947,000,000
Prior Service Cost, Estimated	10,000,000
Net (Gain) Loss, Estimated	(74,000,000)
Georgia Power [Member] | Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	187,000,000	186,000,000
Employee benefit obligations	(418,000,000)	(409,000,000)
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	(4,000,000)	(4,000,000)
Net (Gain) Loss	186,000,000	179,000,000
Prior Service Cost, Estimated	0
Net (Gain) Loss, Estimated	(7,000,000)
Alabama Power [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Prepaid pension costs	0	59,000,000
Other regulatory assets, deferred	1,083,000,000	994,000,000
Current liabilities, other	(38,000,000)	(38,000,000)
Employee benefit obligations	(321,000,000)	(343,000,000)
Accumulated OCI	(27,000,000)	(18,000,000)
Alabama Power [Member] | Pension Plans [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Prepaid pension costs	0	59,000,000
Other regulatory assets, deferred	822,000,000	727,000,000
Current liabilities, other	(8,000,000)	(7,000,000)
Employee benefit obligations	(133,000,000)	(99,000,000)
Alabama Power [Member] | Pension Plans [Member] | Regulatory Assets [Member]
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
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)
Alabama Power [Member] | Other Postretirement Benefits [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	89,000,000	96,000,000
Employee benefit obligations	(147,000,000)	(155,000,000)
Alabama Power [Member] | Other Postretirement Benefits [Member] | Regulatory Assets [Member]
Amounts recognized in the consolidated balance sheets related to company's pension plans
Other regulatory assets, deferred	89,000,000	96,000,000
Amounts related to defined benefit pension Plans that had not yet been recognized in net periodic pension cost along with estimated amortization
Prior Service Cost	22,000,000	26,000,000
Net (Gain) Loss	67,000,000	68,000,000
Prior Service Cost, Estimated	4,000,000
Net (Gain) Loss, Estimated	$ (2,000,000)