LEASES - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lease cost
Operating lease cost	$ 252	$ 297	$ 313
Finance lease cost:
Amortization of ROU assets	24	23	21
Interest on lease obligations	14	13	11
Total finance lease cost	38	36	32
Short-term lease costs	40	64	48
Variable lease cost	47	125	96
Sublease income	0	(1)	1
Total lease cost	377	521	490
Assets Subject to Power Purchase Agreement
Lease cost
Operating lease cost	112	162	165
Alabama Power
Lease cost
Operating lease cost	16	59	58
Finance lease cost:
Amortization of ROU assets	2	1	1
Interest on lease obligations	0	0	0
Total finance lease cost	2	1	1
Short-term lease costs	16	44	15
Variable lease cost	0	13	4
Sublease income	0	0	0
Total lease cost	34	117	78
Alabama Power | Assets Subject to Power Purchase Agreement
Lease cost
Operating lease cost	4	48	47
Georgia Power
Lease cost
Operating lease cost	192	198	208
Finance lease cost:
Amortization of ROU assets	19	15	11
Interest on lease obligations	17	17	16
Total finance lease cost	36	32	27
Short-term lease costs	16	13	24
Variable lease cost	74	105	83
Sublease income	0	0	0
Total lease cost	318	348	342
Georgia Power | Assets Subject to Power Purchase Agreement
Lease cost
Operating lease cost	174	180	184
Mississippi Power
Lease cost
Operating lease cost	5	5	2
Finance lease cost:
Amortization of ROU assets	1	1	1
Interest on lease obligations	0	1	1
Total finance lease cost	1	2	2
Short-term lease costs	0	0	0
Variable lease cost	0	0	0
Sublease income	0	0	0
Total lease cost	6	7	4
Southern Power
Lease cost
Operating lease cost	34	32	33
Finance lease cost:
Amortization of ROU assets	0	0	0
Interest on lease obligations	0	0	0
Total finance lease cost	0	0	0
Short-term lease costs	0	0	0
Variable lease cost	4	5	5
Sublease income	0	0	0
Total lease cost	38	37	38
Southern Company Gas
Lease cost
Operating lease cost	12	15	19
Finance lease cost:
Amortization of ROU assets	0	0	0
Interest on lease obligations	0	0	0
Total finance lease cost	0	0	0
Short-term lease costs	0	0	0
Variable lease cost	0	0	0
Sublease income	0	0	0
Total lease cost	$ 12	$ 15	$ 19