Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Changes in Stockholders' Equity
Beginning Balance, Treasury Shares			(3,400)
Beginning Balance			$ 21,982	$ 20,926
Consolidated net income attributable to Southern Company	$ 1,130	$ 959	2,226	2,096
Other comprehensive income (loss)	$ 22	(15)	(95)	(7)
Stock issued			3,265	136
Stock-based compensation			119	78
Stock repurchased, at cost				(115)
Cash dividends on common stock			(1,553)	(1,465)
Preference stock redemption				(150)
Contributions from noncontrolling interests			357	429
Distributions to noncontrolling interests			(21)	(13)
Purchase of membership interests from noncontrolling interests			(129)
Net income attributable to noncontrolling interests			36	13
Other			$ (7)	(5)
Beginning Balance, Treasury Shares	(800)		(800)
Ending Balance	$ 26,180	$ 21,923	$ 26,180	$ 21,923
Number of Common shares Issued [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares			915,073	908,502
Stock issued, Shares			65,725	3,769
Ending Balance, Shares	980,798	912,271	980,798	912,271
Number of Common shares Treasury [Member]
Changes in Stockholders' Equity
Beginning Balance, Treasury Shares			(3,352)	(725)
Stock issued, Shares			2,599
Stock repurchased, at cost, Shares				(2,599)
Other, Shares			(46)	(8)
Beginning Balance, Treasury Shares	(799)	(3,332)	(799)	(3,332)
Common Stockholders' Equity [Member]
Changes in Stockholders' Equity
Beginning Balance			$ 20,592	$ 19,949
Consolidated net income attributable to Southern Company			2,226	2,096
Other comprehensive income (loss)			(95)	(7)
Stock issued			3,265	136
Stock-based compensation			119	78
Stock repurchased, at cost				(115)
Cash dividends on common stock			(1,553)	(1,465)
Other			(7)	(8)
Ending Balance	$ 24,547	$ 20,664	24,547	20,664
Preferred And Preference Stock [Member]
Changes in Stockholders' Equity
Beginning Balance			609	756
Preference stock redemption				(150)
Other				3
Ending Balance	609	609	609	609
Noncontrolling Interest [Member]
Changes in Stockholders' Equity
Beginning Balance			781	221
Contributions from noncontrolling interests			357	429
Distributions to noncontrolling interests			(21)	(13)
Purchase of membership interests from noncontrolling interests			(129)
Net income attributable to noncontrolling interests			36	13
Ending Balance	$ 1,024	$ 650	$ 1,024	$ 650