Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net cash paid for capitalized interest			$ 72	$ 89	$ 128
Alabama Power
Net cash paid for capitalized interest			22	15	11
Georgia Power
Net cash paid for capitalized interest			26	23	20
Mississippi Power
Net cash paid for capitalized interest			0	29	49
Southern Power
Net cash paid for capitalized interest			17	11	$ 44
Southern Company Gas
Net cash paid for capitalized interest	$ 4		$ 7	$ 11
Southern Company Gas | Southstar
Ownership percentage of noncontrolling interest	15.00%
Predecessor | Southern Company Gas
Net cash paid for capitalized interest		$ 3