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, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			$ 144	$ 151	$ 76
Impairment charges			0	251	2
Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			140	148	50
Impairment charges			0	131	0
Southern Company Gas | SNG
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			139	146	127
Southern Company Gas | PennEast Pipeline
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			0	0	(81)
Impairment charges	$ 2	$ 82	84		84
Southern Company Gas | Other
Schedule of Equity Method Investments [Line Items]
Earnings from equity method investments			$ 1	$ 2	$ 4