CONSOLIDATED ENTITIES AND EQUITY METHOD INVESTMENTS - Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	$ 1,368	$ 1,443
Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	1,235	1,276
SNG | Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	1,202	1,243
Other | Southern Company Gas
Schedule of Equity Method Investments [Line Items]
Equity investments in unconsolidated subsidiaries	$ 33	$ 33