Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 6	$ 6
Lease income - operating leases	49	51
Variable lease income	69	84
Total lease income	124	141
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	18	20
Variable lease income	0	0
Total lease income	18	20
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	7	8
Variable lease income	0	0
Total lease income	7	8
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	4	4
Lease income - operating leases	1	0
Variable lease income	0	0
Total lease income	5	4
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	2	2
Lease income - operating leases	21	21
Variable lease income	75	90
Total lease income	98	113
SOUTHERN Co GAS
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	9	9
Variable lease income	0	0
Total lease income	$ 9	$ 9