Revenue from Contracts with Customers and Lease Income - Schedule of Contract Balances (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 2,946	$ 2,820
Contract Assets	379	271
Contract Liabilities	181	116
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	978	821
Contract Assets	7	2
Contract Liabilities	0	0
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	1,347	1,011
Contract Assets	202	121
Contract Liabilities	49	1
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	111	90
Contract Assets	0	0
Contract Liabilities	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	125	122
Contract Assets	0	0
Contract Liabilities	2	4
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Accounts Receivable	306	684
Contract Assets	71	56
Contract Liabilities	$ 3	$ 0