Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 6	$ 7	$ 11	$ 14
Lease income - operating leases	33	35	66	71
Variable lease income	125	129	207	201
Total lease income	164	171	284	286
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	2	2	3	5
Variable lease income	0	0	1	0
Total lease income	2	2	4	5
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	7	9	14	16
Variable lease income	0	0	0	0
Total lease income	7	9	14	16
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	4	5	7	9
Lease income - operating leases	1	1	1	2
Variable lease income	0	0	0	0
Total lease income	5	6	8	11
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	2	2	4	5
Lease income - operating leases	37	22	73	43
Variable lease income	136	139	225	218
Total lease income	175	163	302	266
SOUTHERN Co GAS
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	9	9	18	18
Variable lease income	0	0	0	0
Total lease income	$ 9	$ 9	$ 18	$ 18