CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Balance Sheet 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]
Equity investments in unconsolidated subsidiaries			$ 1,443	$ 1,282
Impairment charges			251	2	$ 0
Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries			1,276	1,173
Impairment charges			131	0	$ 0
SNG | Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries			1,243	1,129
PennEast Pipeline | Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Impairment charges	$ 2	$ 82	84	84
Dividends paid by equity method investment			11
Other | Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries			$ 33	$ 44