Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 6	$ 7	$ 18	$ 19
Lease income - operating leases	36	50	129	149
Variable lease income	134	139	327	355
Total lease income	176	196	474	523
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	3	19	32	58
Variable lease income	0	0	1	1
Total lease income	3	19	33	59
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	8	22	24
Variable lease income	0	0	0	0
Total lease income	7	8	22	24
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	4	4	11	11
Lease income - operating leases	0	1	2	1
Variable lease income	0	0	0	0
Total lease income	4	5	13	12
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	2	3	7	8
Lease income - operating leases	21	21	64	64
Variable lease income	144	145	351	372
Total lease income	167	169	422	444
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