Revenue from Contracts with Customers and Lease Income - Schedule of Contract Balances (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Accounts Receivable	$ 2,680	$ 3,123
Contract Assets	267	156
Contract Liabilities	62	45
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	858	696
Contract Assets	6	2
Contract Liabilities	0	4
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	1,175	922
Contract Assets	146	89
Contract Liabilities	8	9
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	106	92
Contract Assets	0	0
Contract Liabilities	2	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Accounts Receivable	138	237
Contract Assets	0	0
Contract Liabilities	8	1
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Accounts Receivable	331	1,107
Contract Assets	41	0
Contract Liabilities	$ 0	$ 0