LEASES - Lease Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 25	$ 15	$ 16
Lease income - operating leases	208	223	208
Variable lease income	417	429	419
Total lease income	650	$ 667	643
Operating lease, income, comprehensive income, extensible list, not disclosed, flag		Lease income - operating leases
Alabama Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	$ 0	0
Lease income - operating leases	77	82	45
Variable lease income	1	0	0
Total lease income	78	82	45
Georgia Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0
Lease income - operating leases	32	42	58
Variable lease income	0	0	0
Total lease income	32	42	58
Mississippi Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	15	14	12
Lease income - operating leases	2	2	2
Variable lease income	0	0	0
Total lease income	17	16	14
Southern Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	10	1	0
Lease income - operating leases	85	85	87
Variable lease income	448	456	449
Total lease income	543	542	536
Southern Company Gas
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0
Lease income - operating leases	36	35	35
Variable lease income	0	0	0
Total lease income	$ 36	$ 35	$ 35