CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Income Statement Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			$ 151	$ 76	$ 153
Impairment charges			251	2	0
Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			148	50	141
Impairment charges			131	0	0
Southern Company Gas | SNG
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			146	127	129
Southern Company Gas | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			0	(81)	7
Impairment charges	$ 2	$ 82	84	84
Southern Company Gas | Other
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			$ 2	$ 4	$ 5