Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 6	$ 3
Lease income - operating leases	51	55
Variable lease income	84	84
Total lease income	141	142
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	20	21
Variable lease income	0	0
Total lease income	20	21
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0
Lease income - operating leases	8	10
Variable lease income	0	0
Total lease income	8	10
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	4	3
Lease income - operating leases	0	0
Variable lease income	0	0
Total lease income	4	3
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	2	0
Lease income - operating leases	21	21
Variable lease income	90	90
Total lease income	113	111
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