Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net cash paid for capitalized interest	$ 81	$ 74	$ 72
Alabama Power
Net cash paid for capitalized interest	15	19	22
Georgia Power
Net cash paid for capitalized interest	47	35	26
Mississippi Power
Net cash paid for capitalized interest	0	1	0
Southern Power
Net cash paid for capitalized interest	11	15	17
Southern Company Gas
Net cash paid for capitalized interest	$ 7	$ 6	$ 7