SEGMENT AND RELATED INFORMATION - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) segment state	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Total operating revenues	$ 25,253	$ 29,279	$ 23,113
Total operating revenues	24,828	25,941	23,463
Southern Power
Segment Reporting Information [Line Items]
Total operating revenues	2,189	3,369	2,216
Total operating revenues	1,630	2,805	1,605
Southern Company Gas
Segment Reporting Information [Line Items]
Total operating revenues	4,702	5,962	4,380
Total operating revenues	$ 4,598	5,905	6,293
Number of reportable segments | segment	3
Number of states in which entity operates | state	4
Southern Company Gas | Southern Power
Segment Reporting Information [Line Items]
Total operating revenues			18
Southern Natural Gas Company, LLC | Southern Company Gas
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%
Dalton Pipeline | Southern Company Gas
Segment Reporting Information [Line Items]
Ownership percentage, equity method investment	50.00%
Wholesale revenues, affiliates | Southern Power | Traditional Electric Operating Companies
Segment Reporting Information [Line Items]
Total operating revenues	$ 537	$ 875	$ 515