Revenue from Contracts with Customers and Lease Income - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Disaggregation of Revenue [Line Items]
Contract liabilities	$ 257	$ 213
Contract assets	338	294
Revenue from contracts with customers recognized	55
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	76	75
Contract assets	196	160
Revenue from contracts with customers recognized	11
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0
Contract assets	67	67
Revenue from contracts with customers recognized	0
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	9	6
Contract assets	5	3
Revenue from contracts with customers recognized	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	2	0
Contract assets	0	0
Revenue from contracts with customers recognized	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	1	2
Contract assets	0	0
Revenue from contracts with customers recognized	$ 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
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract liabilities	170	132
Contract assets	$ 69	$ 63