REVENUE FROM CONTRACTS WITH CUSTOMERS - Contract Balances (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 2,820	$ 3,123
Contract Assets	271	156
Contract Liabilities	116	45
Contract with customer, liability, revenue recognized	36	36
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract Assets	91	65
Contract Liabilities	115	32
Alabama Power
Disaggregation of Revenue [Line Items]
Accounts Receivable	821	696
Contract Assets	2	2
Contract Liabilities	0	4
Georgia Power
Disaggregation of Revenue [Line Items]
Accounts Receivable	1,011	922
Contract Assets	121	89
Contract Liabilities	1	9
Mississippi Power
Disaggregation of Revenue [Line Items]
Accounts Receivable	90	92
Contract Assets	0	0
Contract Liabilities	0	0
Southern Power
Disaggregation of Revenue [Line Items]
Accounts Receivable	122	237
Contract Assets	0	0
Contract Liabilities	4	1
Southern Company Gas
Disaggregation of Revenue [Line Items]
Accounts Receivable	684	1,107
Contract Assets	56	0
Contract Liabilities	0	$ 0
Southern Company Gas | Energy Efficiency Enhancement And Upgrade
Disaggregation of Revenue [Line Items]
Contract Liabilities	$ 59