Summary of Significant Accounting Policies - General (Details) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($) state segment utility	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) state segment utility	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Accounting Policies [Line Items]
Other intangible assets, net of amortization	$ 970				$ 317				$ 970	$ 317
Number of traditional operating companies | segment	4								4
Retail Revenues									$ 15,234	14,987	$ 15,550
Net Income (Loss) After Dividends on Preferred and Preference Stock	$ 197	$ 1,139	$ 623	$ 489	271	$ 959	$ 629	$ 508	$ 2,448	2,367	1,963
Southern Company Gas [Member]
Accounting Policies [Line Items]
Number of states in which entity operates | state	7								7
Number of natural gas distribution utilities | utility	7								7
Traditional Operating Companies
Accounting Policies [Line Items]
Number of states in which entity operates | state	4								4
Georgia Power [Member]
Accounting Policies [Line Items]
Retail Revenues									$ 7,772	7,727	8,240
Net Income (Loss) After Dividends on Preferred and Preference Stock	$ 113	599	349	269	196	551	277	236	$ 1,330	1,260	$ 1,225
Southern Power [Member]
Accounting Policies [Line Items]
Other intangible assets, net of amortization					317					$ 317
Net Income (Loss) After Dividends on Preferred and Preference Stock	$ 23	$ 176	$ 89	$ 50	$ 34	$ 102	46	$ 33
Restatement Adjustment | Georgia Power [Member]
Accounting Policies [Line Items]
Retail Revenues							(75)
Net Income (Loss) After Dividends on Preferred and Preference Stock							$ (47)