Consolidated Entities and Equity Method Investments - Schedule of Equity Method Investments (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,287		$ 1,362
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,189		1,290
Asset impairment charges	82	$ 0
Asset impairment charges, net of tax	58
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,143		1,167
SOUTHERN Co GAS | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Investment Balance	13		91
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 33		$ 32