Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Changes in Stockholders' Equity
Beginning balance, treasury shares (in shares)				(800)
Beginning balance				$ 26,612	$ 21,982
Consolidated net income attributable to Southern Company		$ 1,069	$ 1,139	347	2,251
Other comprehensive income (loss)				(2)	(95)
Stock issued				613	3,265
Stock-based compensation				97	94
Cash dividends on common stock				(1,716)	(1,553)
Preference stock redemption				(150)
Contributions from noncontrolling interests				77	357
Distributions to noncontrolling interests				(87)	(21)
Purchase of membership interests from noncontrolling interests					(129)
Net income attributable to noncontrolling interests				45	36
Reclassification from redeemable noncontrolling interests				114
Other				$ (11)	(7)
Ending balance, treasury shares (in shares)		(900)		(900)
Ending balance		$ 25,939	$ 26,180	$ 25,939	$ 26,180
Number of Common Shares Issued
Changes in Stockholders' Equity
Beginning balance (in shares)				991,213	915,073
Stock issued (in shares)				13,308	65,725
Other (in shares)				0
Ending balance (in shares)		1,004,521	980,798	1,004,521	980,798
Number of Common Shares Treasury Issued
Changes in Stockholders' Equity
Beginning balance, treasury shares (in shares)				(819)	(3,352)
Stock issued (in shares)				0	2,599
Other (in shares)				(75)	(46)
Ending balance, treasury shares (in shares)		(894)	(799)	(894)	(799)
Common Stockholders' Equity
Changes in Stockholders' Equity
Beginning balance				$ 24,758	$ 20,592
Consolidated net income attributable to Southern Company				347	2,251
Other comprehensive income (loss)				(2)	(95)
Stock issued				613	3,265
Stock-based compensation				97	94
Cash dividends on common stock				(1,716)	(1,553)
Other				(15)	(7)
Ending balance		$ 24,082	$ 24,547	24,082	24,547
Preferred and Preference Stock of Subsidiaries
Changes in Stockholders' Equity
Beginning balance				609	609
Preference stock redemption				(150)
Other				3
Ending balance		462	609	462	609
Noncontrolling Interest
Changes in Stockholders' Equity
Beginning balance				1,245	781
Contributions from noncontrolling interests				77	357
Distributions to noncontrolling interests				(87)	(21)
Purchase of membership interests from noncontrolling interests					(129)
Net income attributable to noncontrolling interests				45	36
Reclassification from redeemable noncontrolling interests				114
Other				1
Ending balance		$ 1,395	$ 1,024	$ 1,395	$ 1,024
SunPower Corp. | Noncontrolling Interest
Changes in Stockholders' Equity
Beginning balance	$ 114