Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net cash paid for capitalized interest		$ 89	$ 125	$ 124
ALABAMA POWER CO
Net cash paid for capitalized interest		15	11	22
GEORGIA POWER CO
Net cash paid for capitalized interest		23	20	16
GULF POWER CO
Net cash paid for capitalized interest		0	0	6
MISSISSIPPI POWER CO
Net cash paid for capitalized interest		29	49	66
SOUTHERN POWER CO
Net cash paid for capitalized interest		$ 11	$ 44	$ 14
SOUTHERN Co GAS | Southstar
Ownership percentage of noncontrolling interest	15.00%