Consolidated Entities and Equity Method Investments - Schedule of Equity Method Investments (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 1,376	$ 1,443
SOUTHERN Co GAS
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,243	1,276
SOUTHERN Co GAS | SNG
Schedule of Equity Method Investments [Line Items]
Investment Balance	1,210	1,243
SOUTHERN Co GAS | Other
Schedule of Equity Method Investments [Line Items]
Investment Balance	$ 33	$ 33