Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock [Member]	Noncontrolling Interest [Member]	Treasury Stock [Member]	Paid In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Preferred And Preference Stock [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] Noncontrolling Interest [Member]	Southern Power [Member] Common Stockholder's Equity Not Including Noncontrolling Interest [Member]	Southern Power [Member] Paid In Capital [Member]	Southern Power [Member] Retained Earnings [Member]	Southern Power [Member] Accumulated Other Comprehensive Income (Loss) [Member]	Southern Company Gas [Member]	Southern Company Gas [Member] Common Stock [Member]	Southern Company Gas [Member] Noncontrolling Interest [Member]	Southern Company Gas [Member] Treasury Stock [Member]	Southern Company Gas [Member] Paid In Capital [Member]	Southern Company Gas [Member] Retained Earnings [Member]	Southern Company Gas [Member] Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance, Shares (Predecessor [Member]) at Dec. 31, 2013																																					118,889		217
Beginning Balance, Shares at Dec. 31, 2013		892,733		5,647						31,000					9,000					5,000					1,000					0
Beginning Balance (Predecessor [Member]) at Dec. 31, 2013																																				$ 3,613	$ 595	$ 45	$ (8)	$ 2,054	$ 1,063	$ (136)
Beginning Balance at Dec. 31, 2013	$ 19,764	$ 4,461	$ 0	$ (250)	$ 5,362	$ 9,510	$ (75)	$ 756	$ 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	$ 0	$ 1,564	$ 1,029	$ 532	$ 3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																				482					482
Net income	1,963					1,963			761			761		1,225			1,225		140			140		(329)			(329)
Net income attributable to Southern Power Company																													172			172		172
Other comprehensive income (loss) | Predecessor [Member]																																				(72)		(2)				(70)
Other comprehensive income (loss)	(53)						(53)		(3)				(3)	(3)				(3)						1				1
Stock issued, shares | Predecessor [Member]																																					236
Stock issued, shares		15,769		4,996																0
Stock issued | Predecessor [Member]																																				12	$ 1			11
Stock issued	806	$ 78		$ 227	501			0											50	$ 50
Share-based compensation, shares | Predecessor [Member]																																					522
Stock-based compensation | Predecessor [Member]																																				25	$ 3			22
Stock-based compensation	86				86
Capital contributions from parent company									42		42			563		563			7		7			235		235			147			147	147
Cash dividends on common stock | Predecessor [Member]																																				(233)					(233)
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
Distributions to noncontrolling interests | Predecessor [Member]																																				(17)		(17)
Net income (loss) attributable to noncontrolling interests | Predecessor [Member]																																				18		18
Net income (loss) attributable to noncontrolling interests	(2)		(2)																										(2)		(2)
Other, shares				(74)
Other	7		2	$ (3)	6	2								(1)			(1)
Ending Balance, Shares (Predecessor [Member]) at Dec. 31, 2014																																					119,647		217
Ending Balance, Shares at Dec. 31, 2014		908,502		725						31,000					9,000					5,000					1,000					0
Ending Balance (Predecessor [Member]) at Dec. 31, 2014																																				3,828	$ 599	44	$ (8)	2,087	1,312	(206)
Ending Balance at Dec. 31, 2014	20,926	$ 4,539	221	$ (26)	5,955	9,609	(128)	756	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	219	1,752	1,176	573	3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																				353					353
Net income	2,367					2,367			785			785		1,260			1,260		148			148		(8)			(8)
Net income attributable to Southern Power Company																													215			215		215
Other comprehensive income (loss) | Predecessor [Member]																																				20						20
Other comprehensive income (loss)	(2)						(2)		(3)				(3)	(7)				(7)	1				1	1				1	1			1			1
Stock issued, shares | Predecessor [Member]																																					221
Stock issued, shares		6,571		(2,599)																1,000
Stock issued | Predecessor [Member]																																				12	$ 1			11
Stock issued	256	$ 33		$ 0	223														20	$ 20	0
Share-based compensation, shares | Predecessor [Member]																																					509
Stock-based compensation | Predecessor [Member]																																				4	$ 3			1
Stock-based compensation	100				100
Stock repurchased, at cost	(115)			$ (115)
Capital contributions from parent company									37		37			79		79			7		7			281		281			646			646	646
Cash dividends on common stock | Predecessor [Member]																																				(244)					(244)
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 | Predecessor [Member]																																				(18)		(18)
Distributions to noncontrolling interests	(18)		(18)																										(17)		(17)
Net income (loss) attributable to noncontrolling interests | Predecessor [Member]																																				20		20
Net income (loss) attributable to noncontrolling interests	12		12																										12		12
Other, shares				(28)
Other	(2)		(1)	$ (1)	4	(7)		3	(8)			(8)												1			1
Ending Balance, Shares (Predecessor [Member]) at Dec. 31, 2015																																					120,377		217
Ending Balance, Shares at Dec. 31, 2015		915,073		3,352						31,000					9,000					6,000					1,000					0
Ending Balance (Predecessor [Member]) at Dec. 31, 2015																																				3,975	$ 603	46	$ (8)	2,099	1,421	(186)
Ending Balance at Dec. 31, 2015	21,982	$ 4,572	781	$ (142)	6,282	10,010	(130)	609	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	781	2,483	1,822	657	4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																				131					131
Other comprehensive income (loss) | Predecessor [Member]																																				(35)						(35)
Stock issued, shares | Predecessor [Member]																																					95
Stock issued | Predecessor [Member]																																				6				6
Share-based compensation, shares | Predecessor [Member]																																					270
Stock-based compensation | Predecessor [Member]																																				30	$ 2			28
Cash dividends on common stock | Predecessor [Member]																																				(128)					(128)
Ending Balance, Shares (Predecessor [Member]) at Jun. 30, 2016																																					120,742		217
Ending Balance (Successor [Member]) at Jun. 30, 2016																																				8,001				8,001
Ending Balance (Predecessor [Member]) at Jun. 30, 2016																																				3,933	$ 605	0	$ (8)	2,133	1,424	(221)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Noncontrolling Interest, Decrease from Reclassification to Temporary Equity | Predecessor [Member]																																				(46)		(46)
Beginning Balance, Shares (Predecessor [Member]) at Dec. 31, 2015																																					120,377		217
Beginning Balance, Shares at Dec. 31, 2015		915,073		3,352						31,000					9,000					6,000					1,000					0
Beginning Balance (Predecessor [Member]) at Dec. 31, 2015																																				3,975	$ 603	46	$ (8)	2,099	1,421	(186)
Beginning Balance at Dec. 31, 2015	21,982	$ 4,572	781	$ (142)	6,282	10,010	(130)	609	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	781	2,483	1,822	657	4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,448					2,448			822			822		1,330			1,330		131			131		(50)			(50)
Net income attributable to Southern Power Company																													338			338		338
Other comprehensive income (loss)	(50)						(50)		2				2	2				2	1				1	2				2	31			31			31
Stock issued, shares		76,140		2,599
Stock issued	3,758	$ 380		$ 115	3,263
Stock-based compensation	120				120
Capital contributions from parent company									272		272			610		610			22		22			632		632			1,850			1,850	1,850
Cash dividends on common stock	(2,104)					(2,104)			(765)			(765)		(1,305)			(1,305)		(120)			(120)							(272)			(272)		(272)
Contributions from noncontrolling interests	618		618																										618		618
Distributions to noncontrolling interests	(57)		(57)																										(57)		(57)
Purchase of membership interests from noncontrolling interests	(129)		(129)																										(129)		(129)
Net income (loss) attributable to noncontrolling interests	32		32																										32		32
Other, shares				(66)
Other	(6)		0	$ (4)	(4)	2		0																					0				(1)	1
Ending Balance, Shares (Successor [Member]) at Dec. 31, 2016																																					0		0
Ending Balance, Shares at Dec. 31, 2016		991,213		819						31,000					9,000					6,000					1,000					0
Ending Balance (Successor [Member]) at Dec. 31, 2016																																				9,109	$ 0	0	$ 0	9,095	(12)	26
Ending Balance at Dec. 31, 2016	26,612	$ 4,952	1,245	$ (31)	9,661	10,356	(180)	609	6,323	$ 1,222	2,613	2,518	(30)	11,356	$ 398	6,885	4,086	(13)	1,389	$ 503	589	296	1	2,943	$ 38	3,525	(616)	(4)	5,675	$ 0	1,245	4,430	3,671	724	35
Beginning Balance, Shares (Predecessor [Member]) at Jun. 30, 2016																																					120,742		217
Beginning Balance (Successor [Member]) at Jun. 30, 2016																																				8,001				8,001
Beginning Balance (Predecessor [Member]) at Jun. 30, 2016																																				3,933	$ 605	0	$ (8)	2,133	1,424	(221)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																																				114					114
Other comprehensive income (loss) | Successor [Member]																																				26						26
Stock-based compensation | Successor [Member]																																				9				9
Capital contributions from parent company | Successor [Member]																																				1,085				1,085
Cash dividends on common stock | Successor [Member]																																				(126)					(126)
Ending Balance, Shares (Successor [Member]) at Dec. 31, 2016																																					0		0
Ending Balance, Shares at Dec. 31, 2016		991,213		819						31,000					9,000					6,000					1,000					0
Ending Balance (Successor [Member]) at Dec. 31, 2016																																				$ 9,109	$ 0	$ 0	$ 0	$ 9,095	$ (12)	$ 26
Ending Balance at Dec. 31, 2016	$ 26,612	$ 4,952	$ 1,245	$ (31)	$ 9,661	$ 10,356	$ (180)	$ 609	$ 6,323	$ 1,222	$ 2,613	$ 2,518	$ (30)	$ 11,356	$ 398	$ 6,885	$ 4,086	$ (13)	$ 1,389	$ 503	$ 589	$ 296	$ 1	$ 2,943	$ 38	$ 3,525	$ (616)	$ (4)	$ 5,675	$ 0	$ 1,245	$ 4,430	$ 3,671	$ 724	$ 35