Revenue from Contracts with Customers and Lease Income - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Contract liabilities	$ 73	$ 73	$ 45
Contract assets	167	167	156
GEORGIA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	28	28	9
Contract assets	73	73	89
Revenue from contracts with customers recognized	0	0
SOUTHERN Co GAS
Disaggregation of Revenue [Line Items]
Contract liabilities	0	0	0
Contract assets	30	30	0
Revenue from contracts with customers recognized	0	0
ALABAMA POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	1	1	4
Contract assets	0	0	2
Revenue from contracts with customers recognized	0	0
MISSISSIPPI POWER CO
Disaggregation of Revenue [Line Items]
Contract liabilities	3	3	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	1
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	41	$ 41
Unregulated Distributed Generation
Disaggregation of Revenue [Line Items]
Contract liabilities	42	42	32
Contract assets	$ 64	$ 64	$ 65