Condensed Consolidated Statements of Income (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenues	$ 4,620	$ 5,098	$ 9,638	$ 10,510
Cost, Product and Service [Extensible List]	us-gaap:NaturalGasUsRegulatedMember	us-gaap:NaturalGasUsRegulatedMember	us-gaap:NaturalGasUsRegulatedMember	us-gaap:NaturalGasUsRegulatedMember
Alternative revenue programs
Revenues	$ (2)	$ 1	$ 7	$ 0
SOUTHERN Co GAS
Revenues	636	689	1,885	2,163
Revenue taxes collected	22	23	69	78
SOUTHERN Co GAS | Alternative revenue programs
Revenues	$ (2)	$ 1	$ 7	$ 0