LEASES - Lease Income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	$ 24	$ 25	$ 15
Lease income - operating leases	164	208	223
Variable lease income	406	417	429
Total lease income	594	$ 650	667
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	35	77	82
Variable lease income	1	1	0
Total lease income	36	78	82
Georgia Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0
Lease income - operating leases	29	32	42
Variable lease income	0	0	0
Total lease income	29	32	42
Mississippi Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	14	15	14
Lease income - operating leases	2	2	2
Variable lease income	0	0	0
Total lease income	16	17	16
Southern Power
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	10	10	1
Lease income - operating leases	85	85	85
Variable lease income	437	448	456
Total lease income	532	543	542
Southern Company Gas
Lessor, Lease, Description [Line Items]
Lease income - interest income on sales-type leases	0	0	0
Lease income - operating leases	37	36	35
Variable lease income	0	0	0
Total lease income	$ 37	$ 36	$ 35