Income Taxes - Textual (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Tax Disclosure [Line Items]
Net cash payments for income taxes	$ 38,000,000	$ (401,000,000)	$ 276,000,000
Net operating loss carryforward of State of Georgia	827,000,000
Deferred tax assets	3,932,000,000	3,473,000,000
State income tax benefits as a result of utilization of State of Georgia net operating loss carryforward	48,000,000
Tax regulatory assets	1,400,000,000
Tax regulatory liabilities	211,000,000
Amortization of deferred investment tax credits	23,000,000	19,000,000	23,000,000
Unamortized investment tax credits	894,000,000	611,000,000
Percentage of extension bonus depreciation for property acquired	50.00%
Percentage of additional bonus depreciation for property acquired	100.00%
Increase (decrease) in unrecognized tax benefits	50,000,000
Balance of unrecognized tax benefits	70,000,000	120,000,000	296,000,000	199,000,000
Maximum [Member]
Income Tax Disclosure [Line Items]
Recovery and amortization periods for regulatory assets (liabilities), average remaining service period	15 years
Alabama Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments for income taxes	309,000,000	(139,000,000)	188,000,000
Deferred tax assets	1,040,000,000	979,000,000
Tax regulatory assets	525,000,000
Tax regulatory liabilities	79,000,000
Amortization of deferred investment tax credits	8,000,000	8,000,000	8,000,000
Unamortized investment tax credits	141,000,000	149,000,000
Percentage of extension bonus depreciation for property acquired	50.00%
Percentage of additional bonus depreciation for property acquired	100.00%
Increase (decrease) in unrecognized tax benefits	1,000,000
Balance of unrecognized tax benefits	31,000,000	32,000,000	43,000,000	6,000,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Alabama Power [Member] | Maximum [Member]
Income Tax Disclosure [Line Items]
Recovery and amortization periods for regulatory assets (liabilities), average remaining service period	15 years
Georgia Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments for income taxes	312,000,000	54,000,000	149,000,000
Deferred tax assets	1,656,000,000	1,402,000,000
Tax regulatory assets	738,000,000
Recovery and amortization periods for regulatory assets (liabilities), average remaining service period	14 years
Tax regulatory liabilities	151,000,000
Regulatory Liabilities		62,000,000
Amortization of deferred investment tax credits	13,000,000	9,000,000	13,000,000
State Investment Tax Credit	86,000,000
Unamortized investment tax credits	208,000,000	220,000,000
Percentage of extension bonus depreciation for property acquired	50.00%
Percentage of additional bonus depreciation for property acquired	100.00%
Increase (decrease) in unrecognized tax benefits	(24,000,000)
Balance of unrecognized tax benefits	23,000,000	47,000,000	237,000,000	181,000,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Gulf Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments for income taxes	(96,639,000)	(26,345,000)	17,224,000
Deferred tax assets	157,901,000	131,299,000
Tax regulatory assets	50,500,000
Tax regulatory liabilities	6,500,000
Amortization of deferred investment tax credits	1,400,000	1,300,000	1,500,000
Unamortized investment tax credits	5,408,000	6,760,000
Percentage of extension bonus depreciation for property acquired	50.00%
Percentage of additional bonus depreciation for property acquired	100.00%
Increase (decrease) in unrecognized tax benefits	2,100,000
Balance of unrecognized tax benefits	5,007,000	2,892,000	3,870,000	1,639,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Gulf Power [Member] | Maximum [Member]
Income Tax Disclosure [Line Items]
Recovery and amortization periods for regulatory assets (liabilities), average remaining service period	14 years
Mississippi Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments for income taxes	(77,580,000)	(41,024,000)	7,546,000
Deferred tax assets	419,836,000	296,533,000
Tax regulatory assets	73,000,000
Recovery and amortization periods for regulatory assets (liabilities), average remaining service period	14 years
Tax regulatory liabilities	11,200,000
Amortization of deferred investment tax credits	1,200,000	1,300,000	1,300,000
Unamortized investment tax credits	370,554,000	109,761,000
Unamortized investment tax credits, unable to utiilize until 2013 or thereafter	170,900,000
Carryforward Term For Unused Credits	20 years
Percentage of extension bonus depreciation for property acquired	50.00%
Percentage of additional bonus depreciation for property acquired	100.00%
Additional bonus depreciation for property acquired future periods	50.00%
Investment tax credits received	(82,464,000)	0	(22,173,000)
Increase (decrease) in unrecognized tax benefits	800,000
Balance of unrecognized tax benefits	5,755,000	4,964,000	4,288,000	3,026,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Southern Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments for income taxes	(175,269,000)	(26,486,000)	(6,246,000)
Deferred Tax Asset, Reimbursable	3,900,000
Net operating loss carryforward of State of Georgia	117,700,000	88,700,000
Deferred tax assets	91,700,000	84,800,000
Valuation Allowance, Amount	4,000,000	3,000,000
Operating Loss Carryforwards In Year Three	4,200,000
Operating Loss Carryforwards In Year Five	1,200,000
Increase (decrease) in deferred tax assets valuation allowance	(1,000,000)
Percentage of extension bonus depreciation for property acquired	50.00%
Percentage of additional bonus depreciation for property acquired	100.00%
Investment tax credits received	(45,047,000)	(84,723,000)	(26,400,000)
Increase (decrease) in unrecognized tax benefits	300,000
Balance of unrecognized tax benefits	2,900,000	2,600,000	2,300,000	100,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Kemper IGCC [Member] | Mississippi Power [Member]
Income Tax Disclosure [Line Items]
Unamortized investment tax credits	361,600,000
Accounts Payable - Affiliated Companies [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Asset, Reimbursable	1,300,000
Gulf Power [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Liability, Reimbursable	3,100,000
Gulf Power [Member] | Receivables - Affiliated Companies [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Deferred Tax Liability, Reimbursable	300,000
Operating Loss Carryforward [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	5,400,000	4,000,000
Investment tax credit carryforward [Member] | Mississippi Power [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	170,938,000	77,400,000
Investment tax credit carryforward [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	28,600,000	21,800,000
Investment tax credit carryforward [Member] | Nacogdoches Biomass Generating Plant [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforward	45,000,000	84,700,000	26,400,000
Deferred Tax Assets, Tax Credit Carryforwards, Amount Earned in Prior Year		42,900,000
Investment tax credits received	(6,900,000)	(7,300,000)	(6,900,000)
Investment tax credit carryforward [Member] | Plant Cimarron [Member] | Southern Power [Member]
Income Tax Disclosure [Line Items]
Investment tax credits received		$ (4,600,000)