Condensed Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues	$ 5,620	$ 5,995	$ 15,258	$ 16,505
Cost, Product and Service [Extensible List]			us-gaap:NaturalGasUsRegulatedMember
Alternative revenue programs
Revenues	(1)	0	$ 6	0
SOUTHERN Co GAS
Revenues	477	498	2,362	2,661
Revenue taxes collected	10	10	79	88
SOUTHERN Co GAS | Alternative revenue programs
Revenues	$ (1)	$ 0	$ 6	$ 0