Revenue from Contracts with Customers and Lease Income - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2025	Dec. 31, 2024
Disaggregation of Revenue [Line Items]
Contract liabilities	$ 170	$ 170	$ 140
Contract assets	304	304	323
Revenue from contracts with customers recognized	44	72
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	73	73	34
Contract assets	134	134	184
Revenue from contracts with customers recognized	11	16
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0	3
Contract assets	74	74	72
Revenue from contracts with customers recognized	0	0
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	14	14	11
Contract assets	0	0	3
Revenue from contracts with customers recognized	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	2	2	0
Contract assets	0	0	0
Revenue from contracts with customers recognized	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	1	1	2
Contract assets	0	0	0
Revenue from contracts with customers recognized	0	$ 0
Retail Customer Fixed Bill Programs | GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract term		1 year
Energy Efficiency Enhancement And Upgrade | SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract liabilities	68	$ 68
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract liabilities	81	81	95
Contract assets	$ 95	$ 95	$ 67