Revenue from Contracts with Customers and Lease Income - Schedule of Contract Balances (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 2,793	$ 2,820
Contract Assets	290	271
Contract Liabilities	207	116
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	737	821
Contract Assets	3	2
Contract Liabilities	0	0
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	986	1,011
Contract Assets	119	121
Contract Liabilities	19	1
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	80	90
Contract Assets	0	0
Contract Liabilities	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	80	122
Contract Assets	0	0
Contract Liabilities	1	4
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Accounts Receivable	699	684
Contract Assets	59	56
Contract Liabilities	$ 0	$ 0