Income Taxes - Textual (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Line Items]
Net cash payments/(refunds) for income taxes	$ 272,000,000	$ 139,000,000	$ 38,000,000
Net operating loss carryforward	701,000,000
State income tax benefits as a result of utilization of State of Georgia net operating loss carryforward	41,000,000
Deferred tax assets	5,241,000,000	3,624,000,000
Tax Credit Carryforward, Amount	379,000,000
State Investment Tax Credit	159,000,000
Tax regulatory assets	1,500,000,000
Tax regulatory liabilities	192,000,000
Amortization of deferred investment tax credits	22,000,000	16,000,000	23,000,000
Unamortized investment tax credits	1,208,000,000	966,000,000
Unrecognized Tax Benefits	170,000,000	7,000,000	70,000,000	120,000,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Kemper IGCC [Member]
Income Tax Disclosure [Line Items]
Unrecognized Tax Benefits	160,000,000
Alabama Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments/(refunds) for income taxes	436,000,000	296,000,000	309,000,000
Deferred tax assets	1,141,000,000	938,000,000
Tax regulatory assets	526,000,000
Tax regulatory liabilities	72,000,000
Amortization of deferred investment tax credits	8,000,000	8,000,000	8,000,000
Unamortized investment tax credits	125,000,000	133,000,000
Unrecognized Tax Benefits		0	31,000,000	32,000,000
Georgia Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments/(refunds) for income taxes	507,000,000	298,000,000	312,000,000
Deferred tax assets	1,737,000,000	1,464,000,000
State Investment Tax Credit	34,000,000	27,000,000	36,000,000
Tax regulatory assets	702,000,000
Tax regulatory liabilities	106,000,000
Regulatory Liabilities				62,000,000
Amortization of deferred investment tax credits	10,000,000	5,000,000	13,000,000
Federal Tax Credits	5,000,000
State Investment Tax Credit Carryforward	152,000,000
Unamortized investment tax credits	196,000,000	203,000,000
Unrecognized Tax Benefits		0	23,000,000	47,000,000
Gulf Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments/(refunds) for income taxes	44,125,000	(10,727,000)	(96,639,000)
Deferred tax assets	171,427,000	133,006,000
Tax regulatory assets	56,300,000
Tax regulatory liabilities	3,900,000
Amortization of deferred investment tax credits	1,300,000	1,400,000	1,400,000
Unamortized investment tax credits	2,783,000	4,055,000
Unrecognized Tax Benefits	46,000	45,000	5,007,000	2,892,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Mississippi Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments/(refunds) for income taxes	(379,158,000)	(134,198,000)	(77,580,000)
Deferred tax assets	1,251,439,000	673,467,000
Tax Credit Carryforward, Amount	276,400,000
Tax regulatory assets	226,200,000
Tax regulatory liabilities	9,400,000
Amortization of deferred investment tax credits	1,400,000	1,200,000	1,200,000
Unamortized investment tax credits	282,816,000	284,248,000
Minimum Percentage of Carbon Dioxide That Must Capture and Sequester to Remain Eligible for Tax Credits	65.00%
Unrecognized Tax Benefits	164,821,000	3,840,000	5,755,000	4,964,000
Mississippi Power [Member] | Kemper IGCC [Member]
Income Tax Disclosure [Line Items]
Unamortized investment tax credits	276,400,000
Southern Power [Member]
Income Tax Disclosure [Line Items]
Net cash payments/(refunds) for income taxes	(219,641,000)	(226,179,000)	(175,269,000)
Net operating loss carryforward	246,600,000	240,800,000
Deferred tax assets	480,200,000	127,700,000
Increase (decrease) in deferred tax assets valuation allowance	15,100,000
Operating Loss Carryforwards In Year Three	87,000,000
Operating Loss Carryforwards In Year Four	40,000,000
Amortization of deferred investment tax credits	11,399,000	5,535,000	2,633,000
Unrecognized Tax Benefits	4,700,000	1,500,000	2,900,000	2,600,000
Significantly increase or decrease in the amount of the unrecognized tax benefits associated with a majority of Southern	12 months
Southern Power [Member] | Operating Loss Carryforward [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	9,400,000	11,000,000
Southern Power [Member] | Investment tax credit carryforward [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	101,500,000	58,000,000
Southern Power [Member] | Investment tax credit carryforward [Member] | Nacogdoches Biomass Generating Plant [Member]
Income Tax Disclosure [Line Items]
Tax credit carryforward	73,500,000	158,100,000	45,000,000
Reduction in income tax expense, investment tax credits	$ (47,500,000)	$ (31,300,000)	$ (7,800,000)