Stockholders' Equity - Earnings per Share (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings per Share
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	15	16	1	17
Southern Company [Member]
Earnings per Share
As reported shares	910	898	910	894
Effect of options and performance share award units	2	4	3	4
Diluted shares	912	902	913	898