Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 5	$ 6	$ 18	$ 18
Lease income - operating leases	38	36	108	129
Variable lease income	142	134	343	327
Total lease income	185	176	469	474
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	3	6	32
Variable lease income	0	0	0	1
Total lease income	2	3	6	33
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	13	7	28	22
Variable lease income	0	0	0	0
Total lease income	13	7	28	22
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	3	4	11	11
Lease income - operating leases	0	0	2	2
Variable lease income	0	0	0	0
Total lease income	3	4	13	13
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	2	2	7	7
Lease income - operating leases	20	21	63	64
Variable lease income	152	144	370	351
Total lease income	174	167	440	422
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	27	27
Variable lease income	0	0	0	0
Total lease income	$ 9	$ 9	$ 27	$ 27