Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Paid In Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [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] AOCI Attributable to Parent [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] AOCI Attributable to Parent [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] AOCI Attributable to Parent [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] AOCI Attributable to Parent [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] AOCI Attributable to Parent [Member]	Southern Power [Member] Common Stockholder's Equity Not Including Noncontrolling Interest [Member]	Southern Power [Member] Noncontrolling Interest [Member]
Beginning Balance, Shares at Dec. 31, 2012		877,803	10,035							31,000					9,000					5,000					1,000					0
Beginning Balance at Dec. 31, 2012	$ 19,004	$ 4,389	$ (450)	$ 4,855	$ 9,626	$ (123)	$ 707	$ 0	$ 5,398	$ 1,222	$ 2,227	$ 1,976	$ (27)	$ 9,273	$ 398	$ 5,585	$ 3,297	$ (7)	$ 1,181	$ 393	$ 549	$ 241	$ (2)	$ 1,749	$ 38	$ 1,401	$ 319	$ (9)	$ 1,522	$ 0	$ 1,028	$ 495	$ (1)	$ 1,522	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Southern Power Company																													166			166		166
Net income after dividends on preferred and preference stock	1,644				1,644				712			712		1,174			1,174		124			124		(477)			(477)
Capital contributions from parent company									35		35			48		48			4		4			976		976			1		1			1
Other comprehensive income (loss)	48					48			1				1	2				2	1				1	1				1	4				4	4
Stock issued, shares		14,930	4,443																	0
Stock issued	765	$ 72	$ 203	441			49												40	$ 40
Stock-based compensation	65			65
Cash dividends on common stock	(1,762)				(1,762)				(644)			(644)		(907)			(907)		(115)			(115)		(72)			(72)		(129)			(129)		(129)
Other, shares			(55)
Other	0		$ (3)	1	2									1			1
Ending Balance, Shares at Dec. 31, 2013		892,733	5,647							31,000					9,000					5,000					1,000					0
Ending Balance at Dec. 31, 2013	19,764	$ 4,461	$ (250)	5,362	9,510	(75)	756	0	5,502	$ 1,222	2,262	2,044	(26)	9,591	$ 398	5,633	3,565	(5)	1,235	$ 433	553	250	(1)	2,177	$ 38	2,377	(230)	(8)	1,564	$ 0	1,029	532	3	1,564	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Southern Power Company																													172			172		172
Net income after dividends on preferred and preference stock	1,963				1,963				761			761		1,225			1,225		140			140		(329)			(329)
Capital contributions from parent company									42		42			563		563			7		7			235		235			147		147			147
Other comprehensive income (loss)	(53)					(53)			(3)				(3)	(3)				(3)	0					1				1	0
Stock issued, shares		15,769	4,996																	0
Stock issued	806	$ 78	$ 227	501															50	$ 50	0
Stock-based compensation	86			86
Cash dividends on common stock	(1,866)				(1,866)				(550)			(550)		(954)			(954)		(123)			(123)							(131)			(131)		(131)
Contributions from noncontrolling interests	221							221																					221						221
Net income (loss) attributable to noncontrolling interests	2							2																					(2)						(2)
Other, shares			(74)
Other	7		$ (3)	6	2			2						(1)			(1)
Ending Balance, Shares at Dec. 31, 2014		908,502	725							31,000					9,000					5,000					1,000					0
Ending Balance at Dec. 31, 2014	20,926	$ 4,539	$ (26)	5,955	9,609	(128)	756	221	5,752	$ 1,222	2,304	2,255	(29)	10,421	$ 398	6,196	3,835	(8)	1,309	$ 483	560	267	(1)	2,084	$ 38	2,612	(559)	(7)	1,971	$ 0	1,176	573	3	1,752	219
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to Southern Power Company																													215			215		215
Net income after dividends on preferred and preference stock	2,367				2,367				785			785		1,260			1,260		148			148		(8)			(8)
Capital contributions from parent company									37		37			79		79			7		7			281		281			646		646			646
Other comprehensive income (loss)	(2)					(2)			(3)				(3)	(7)				(7)	1				1	1				1	1				1	1
Stock issued, shares		6,571	2,599																	1,000
Stock issued	256	$ 33		223															20	$ 20
Stock-based compensation	100			100
Stock repurchased, at cost	(115)		$ (115)
Cash dividends on common stock	(1,959)				(1,959)				(571)			(571)		(1,034)			(1,034)		(130)			(130)							(131)			(131)		(131)
Preference stock redemptions	(150)						(150)
Contributions from noncontrolling interests	567							567																					567						567
Distributions to noncontrolling interests	(18)							(18)																					(17)						(17)
Net income (loss) attributable to noncontrolling interests	(12)							(12)																					12						12
Other, shares			(28)
Other	(2)		$ (1)	4	(7)		(3)	(1)	(8)			(8)												1			1
Ending Balance, Shares at Dec. 31, 2015		915,073	3,352							31,000					9,000					6,000					1,000					0
Ending Balance at Dec. 31, 2015	$ 21,982	$ 4,572	$ (142)	$ 6,282	$ 10,010	$ (130)	$ 609	$ 781	$ 5,992	$ 1,222	$ 2,341	$ 2,461	$ (32)	$ 10,719	$ 398	$ 6,275	$ 4,061	$ (15)	$ 1,355	$ 503	$ 567	$ 285	$ 0	$ 2,359	$ 38	$ 2,893	$ (566)	$ (6)	$ 3,264	$ 0	$ 1,822	$ 657	$ 4	$ 2,483	$ 781