Consolidated Statements of Common Stockholders Equity (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	Total		Common Stock [Member]	Treasury Stock [Member]	Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Preferred And Preference Stock [Member]	Noncontrolling Interest [Member]	Alabama Power [Member]	Alabama Power [Member] Common Stock [Member]	Alabama Power [Member] Paid In Capital [Member]	Alabama Power [Member] Retained Earnings [Member]	Alabama Power [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Georgia Power [Member]	Georgia Power [Member] Common Stock [Member]	Georgia Power [Member] Paid In Capital [Member]	Georgia Power [Member] Retained Earnings [Member]	Georgia Power [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Gulf Power [Member]	Gulf Power [Member] Common Stock [Member]	Gulf Power [Member] Paid In Capital [Member]	Gulf Power [Member] Retained Earnings [Member]	Gulf Power [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Mississippi Power [Member]	Mississippi Power [Member] Common Stock [Member]	Mississippi Power [Member] Paid In Capital [Member]	Mississippi Power [Member] Retained Earnings [Member]	Mississippi Power [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Southern Power [Member]	Southern Power [Member] Common Stock [Member]	Southern Power [Member] Paid In Capital [Member]	Southern Power [Member] Retained Earnings [Member]	Southern Power [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Southern Power [Member] Common Stockholder's Equity Not Including Noncontrolling Interest [Member]	Southern Power [Member] Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2011	$ 18,285,000,000		$ 4,328,000,000	$ (17,000,000)	$ 4,410,000,000	$ 8,968,000,000	$ (111,000,000)	$ 707,000,000	$ 0	$ 5,342,000,000	$ 1,222,000,000	$ 2,182,000,000	$ 1,956,000,000	$ (18,000,000)	$ 9,023,000,000	$ 398,000,000	$ 5,522,000,000	$ 3,112,000,000	$ (9,000,000)	$ 1,124,948,000	$ 353,060,000	$ 542,709,000	$ 231,333,000	$ (2,154,000)	$ 1,049,217,000	$ 37,691,000	$ 694,855,000	$ 325,568,000	$ (8,897,000)	$ 1,468,682,000	$ 0	$ 1,028,210,000	$ 447,301,000	$ (6,829,000)	$ 1,468,682,000
Beginning Balance, Shares at Dec. 31, 2011			865,664	539							31,000					9,000					4,143					1,121					1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Southern Power Company																														175,285,000			175,285,000		175,285,000
Net income after dividends on preferred and preference stock	2,350,000,000	[1]				2,350,000,000				704,000,000			704,000,000		1,168,000,000			1,168,000,000		125,932,000			125,932,000		99,942,000			99,942,000
Capital contributions from parent company										45,000,000		45,000,000			63,000,000		63,000,000			5,089,000		5,089,000			706,665,000		706,665,000			(662,000)		(662,000)			(662,000)
Other comprehensive income (loss)	(12,000,000)						(12,000,000)			(9,000,000)				(9,000,000)	2,000,000				2,000,000	573,000				573,000	184,000				184,000	6,053,000				6,053,000	6,053,000
Stock issued, shares			12,139																		400
Stock issued	397,000,000		61,000,000		336,000,000															40,000,000	40,000,000
Stock repurchased, at cost, shares				(9,440)
Stock repurchased, at cost	(430,000,000)			(430,000,000)
Stock-based compensation	106,000,000				106,000,000
Cash dividends on common stock	(1,693,000,000)					(1,693,000,000)				(684,000,000)			(684,000,000)		(983,000,000)			(983,000,000)		(115,800,000)			(115,800,000)		(106,800,000)			(106,800,000)		(127,000,000)			(127,000,000)		(127,000,000)
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 1.9425
Capital contributions from noncontrolling interests																														0
Other, shares				(56)
Other	1,000,000			(3,000,000)	3,000,000	1,000,000																								(1,000)			(1,000)
Ending Balance at Dec. 31, 2012	19,004,000,000		4,389,000,000	(450,000,000)	4,855,000,000	9,626,000,000	(123,000,000)		0	5,398,000,000	1,222,000,000	2,227,000,000	1,976,000,000	(27,000,000)	9,273,000,000	398,000,000	5,585,000,000	3,297,000,000	(7,000,000)	1,180,742,000	393,060,000	547,798,000	241,465,000	(1,581,000)	1,749,208,000	37,691,000	1,401,520,000	318,710,000	(8,713,000)	1,522,357,000	0	1,027,548,000	495,585,000	(776,000)	1,522,357,000
Ending Balance, Shares at Dec. 31, 2012			877,803	10,035							31,000					9,000					4,543					1,121					1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after dividends on preferred and preference stock	81,000,000									141,000,000					197,000,000					21,792,000					(246,321,000)					29,192,000
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 0.4900
Ending Balance at Mar. 31, 2013
Beginning Balance at Dec. 31, 2012	19,004,000,000		4,389,000,000	(450,000,000)	4,855,000,000	9,626,000,000	(123,000,000)	707,000,000	0	5,398,000,000	1,222,000,000	2,227,000,000	1,976,000,000	(27,000,000)	9,273,000,000	398,000,000	5,585,000,000	3,297,000,000	(7,000,000)	1,180,742,000	393,060,000	547,798,000	241,465,000	(1,581,000)	1,749,208,000	37,691,000	1,401,520,000	318,710,000	(8,713,000)	1,522,357,000	0	1,027,548,000	495,585,000	(776,000)	1,522,357,000
Beginning Balance, Shares at Dec. 31, 2012			877,803	10,035							31,000					9,000					4,543					1,121					1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Southern Power Company																														165,533,000			165,533,000		165,533,000
Net income after dividends on preferred and preference stock	1,644,000,000	[1],[2]				1,644,000,000				712,000,000			712,000,000		1,174,000,000			1,174,000,000		124,429,000			124,429,000		(476,625,000)			(476,625,000)
Capital contributions from parent company										35,000,000		35,000,000			48,000,000		48,000,000			4,883,000		4,883,000			975,075,000		975,075,000			1,487,000		1,487,000			1,487,000
Other comprehensive income (loss)	48,000,000						48,000,000			1,000,000				1,000,000	2,000,000				2,000,000	472,000				472,000	849,000				849,000	3,695,000				3,695,000	3,695,000
Stock issued, shares			14,930	4,443																	400
Stock issued	765,000,000		72,000,000	203,000,000	441,000,000			49,000,000												40,000,000	40,000,000	0
Stock-based compensation	65,000,000				65,000,000
Cash dividends on common stock	(1,762,000,000)					(1,762,000,000)				(644,000,000)			(644,000,000)		(907,000,000)			(907,000,000)		(115,400,000)			(115,400,000)		(71,956,000)			(71,956,000)		(129,120,000)			(129,120,000)		(129,120,000)
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 2.0125
Capital contributions from noncontrolling interests																														0
Other, shares				(55)
Other	0			(3,000,000)	1,000,000	2,000,000									1,000,000			1,000,000
Ending Balance at Dec. 31, 2013	19,764,000,000		4,461,000,000	(250,000,000)	5,362,000,000	9,510,000,000	(75,000,000)	756,000,000		5,502,000,000	1,222,000,000	2,262,000,000	2,044,000,000	(26,000,000)	9,591,000,000	398,000,000	5,633,000,000	3,565,000,000	(5,000,000)	1,235,126,000	433,060,000	552,681,000	250,494,000	(1,109,000)	2,176,551,000	37,691,000	2,376,595,000	(229,871,000)	(7,864,000)	1,563,952,000	0	1,029,035,000	531,998,000	2,919,000	1,563,952,000
Ending Balance, Shares at Dec. 31, 2013			892,733	5,647							31,000					9,000					4,943					1,121					1
Beginning Balance at Sep. 30, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after dividends on preferred and preference stock	414,000,000									140,000,000					208,000,000					25,301,000					12,921,000					23,266,000
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 0.5075
Ending Balance at Dec. 31, 2013	19,764,000,000									5,502,000,000	1,222,000,000				9,591,000,000	398,000,000				1,235,126,000					2,176,551,000	37,691,000				1,563,952,000	0
Ending Balance, Shares at Dec. 31, 2013											31,000					9,000										1,121					1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after dividends on preferred and preference stock	351,000,000									187,000,000					266,000,000					36,743,000					(172,048,000)					33,471,000
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 0.5075
Ending Balance at Mar. 31, 2014
Beginning Balance at Dec. 31, 2013	19,764,000,000		4,461,000,000	(250,000,000)	5,362,000,000	9,510,000,000	(75,000,000)	756,000,000	0	5,502,000,000	1,222,000,000	2,262,000,000	2,044,000,000	(26,000,000)	9,591,000,000	398,000,000	5,633,000,000	3,565,000,000	(5,000,000)	1,235,126,000	433,060,000	552,681,000	250,494,000	(1,109,000)	2,176,551,000	37,691,000	2,376,595,000	(229,871,000)	(7,864,000)	1,563,952,000	0	1,029,035,000	531,998,000	2,919,000	1,563,952,000
Beginning Balance, Shares at Dec. 31, 2013			892,733	5,647							31,000					9,000					4,943					1,121					1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Southern Power Company																														172,300,000			172,300,000		172,300,000
Net income after dividends on preferred and preference stock	1,963,000,000	[1],[2]				1,963,000,000				761,000,000			761,000,000		1,225,000,000			1,225,000,000		140,176,000			140,176,000		(328,681,000)			(328,681,000)
Capital contributions from parent company										42,000,000		42,000,000			563,000,000		563,000,000			7,116,000		7,116,000			235,541,000		235,541,000			146,357,000		146,357,000			146,357,000
Other comprehensive income (loss)	(53,000,000)						(53,000,000)			(3,000,000)				(3,000,000)	(3,000,000)				(3,000,000)	372,000				372,000	849,000				849,000	367,000				367,000	367,000
Stock issued, shares			15,769	4,996																	500
Stock issued	806,000,000		78,000,000	227,000,000	501,000,000			0												50,000,000	50,000,000
Stock-based compensation	86,000,000				86,000,000
Cash dividends on common stock	(1,866,000,000)					(1,866,000,000)				(550,000,000)			(550,000,000)		(954,000,000)			(954,000,000)		(123,200,000)			(123,200,000)							(131,120,000)			(131,120,000)		(131,120,000)
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 2.0825
Capital contributions from noncontrolling interests	221,000,000								221,000,000																					220,734,000						220,734,000
Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable	2,000,000								2,000,000																					(1,246,000)						(1,246,000)
Other, shares				(74)
Other	7,000,000			(3,000,000)	6,000,000	2,000,000			2,000,000						(1,000,000)			(1,000,000)
Ending Balance at Dec. 31, 2014	20,926,000,000		4,539,000,000	(26,000,000)	5,955,000,000	9,609,000,000	(128,000,000)	756,000,000	221,000,000	5,752,000,000	1,222,000,000	2,304,000,000	2,255,000,000	(29,000,000)	10,421,000,000	398,000,000	6,196,000,000	3,835,000,000	(8,000,000)	1,309,590,000	483,060,000	559,797,000	267,470,000	(737,000)	2,084,260,000	37,691,000	2,612,136,000	(558,552,000)	(7,015,000)	1,971,344,000	0	1,175,392,000	573,178,000	3,286,000	1,751,856,000	219,488,000
Ending Balance, Shares at Dec. 31, 2014			908,502	725							31,000					9,000					5,443					1,121					1
Beginning Balance at Sep. 30, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income after dividends on preferred and preference stock	283,000,000									119,000,000					123,000,000					22,789,000					(24,058,000)					44,386,000
Common Stock, Dividends, Per Share, Cash Paid (in dollars per share)	$ 0.525
Ending Balance at Dec. 31, 2014	$ 20,926,000,000									$ 5,752,000,000	$ 1,222,000,000				$ 10,421,000,000	$ 398,000,000				$ 1,309,590,000					$ 2,084,260,000	$ 37,691,000				$ 1,971,344,000	$ 0
Ending Balance, Shares at Dec. 31, 2014											31,000					9,000										1,121					1

[1] After dividends on preferred and preference stock of subsidiaries.

[2] Segment net income (loss) for the traditional operating companies in 2014 and 2013 includes $868 million in pre-tax charges ($536 million after tax) and $1.2 billion in pre-tax charges ($729 million after tax), respectively, for estimated probable losses on the Kemper IGCC. See Note 3 under "Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate" for additional information.