Revenue from Contracts with Customers and Lease Income - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Contract liabilities	$ 181	$ 181	$ 116
Contract assets	379	379	271
Revenue from contracts with customers recognized	20	97
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	49	49	1
Contract assets	202	202	121
Revenue from contracts with customers recognized	0	0
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract liabilities	3	3	0
Contract assets	71	71	56
Revenue from contracts with customers recognized	0	0
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0	0
Contract assets	7	7	2
Revenue from contracts with customers recognized	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0	0
Contract assets	0	0	0
Revenue from contracts with customers recognized	0	0
SOUTHERN POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	2	2	4
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	132	132	115
Contract assets	$ 102	$ 102	$ 91