Revenue from Contracts with Customers and Lease Income - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2026	Dec. 31, 2025
Disaggregation of Revenue [Line Items]
Contract liabilities	$ 329	$ 329	$ 213
Contract assets	354	354	294
Revenue from contracts with customers recognized	26	80
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	123	123	75
Contract assets	189	189	160
Revenue from contracts with customers recognized	7	18
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0	0
Contract assets	67	67	67
Revenue from contracts with customers recognized	0	0
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	7	7	6
Contract assets	0	0	3
Revenue from contracts with customers recognized	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0	0
Contract assets	4	4	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	199	199	132
Contract assets	$ 92	$ 92	$ 63

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