Revenue from Contracts with Customers and Lease Income - Schedule of Lease Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 7	$ 4	$ 19	$ 11
Lease income - operating leases	50	56	149	168
Variable lease income	139	143	355	355
Total lease income	196	203	523	534
ALABAMA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	19	21	58	62
Variable lease income	0	0	1	0
Total lease income	19	21	59	62
GEORGIA POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0	0
Lease income - operating leases	8	11	24	31
Variable lease income	0	0	0	0
Total lease income	8	11	24	31
MISSISSIPPI POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	4	4	11	10
Lease income - operating leases	1	0	1	1
Variable lease income	0	0	0	0
Total lease income	5	4	12	11
SOUTHERN POWER CO
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	3	0	8	0
Lease income - operating leases	21	21	64	64
Variable lease income	145	151	372	379
Total lease income	169	172	444	443
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	26
Variable lease income	0	0	0	0
Total lease income	$ 9	$ 9	$ 27	$ 26