LEASES - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Lease cost
Operating lease cost	$ 297	$ 313	$ 309
Finance lease cost:
Amortization of ROU assets	23	21	26
Interest on lease obligations	13	11	11
Total finance lease cost	36	32	37
Short-term lease costs	64	48	39
Variable lease cost	125	96	91
Sublease income	(1)	1	0
Total lease cost	521	490	476
Assets Subject to Power Purchase Agreement
Lease cost
Operating lease cost	162	165	161
Alabama Power
Lease cost
Operating lease cost	59	58	55
Finance lease cost:
Amortization of ROU assets	1	1	1
Interest on lease obligations	0	0	0
Total finance lease cost	1	1	1
Short-term lease costs	44	15	11
Variable lease cost	13	4	4
Sublease income	0	0	(1)
Total lease cost	117	78	70
Alabama Power | Assets Subject to Power Purchase Agreement
Lease cost
Operating lease cost	48	47	43
Georgia Power
Lease cost
Operating lease cost	198	208	212
Finance lease cost:
Amortization of ROU assets	15	11	15
Interest on lease obligations	17	16	16
Total finance lease cost	32	27	31
Short-term lease costs	13	24	26
Variable lease cost	105	83	76
Sublease income	0	0	0
Total lease cost	348	342	345
Georgia Power | Assets Subject to Power Purchase Agreement
Lease cost
Operating lease cost	180	184	184
Mississippi Power
Lease cost
Operating lease cost	5	2	3
Finance lease cost:
Amortization of ROU assets	1	1	0
Interest on lease obligations	1	1	0
Total finance lease cost	2	2	0
Short-term lease costs	0	0	0
Variable lease cost	0	0	0
Sublease income	0	0	0
Total lease cost	7	4	3
Southern Power
Lease cost
Operating lease cost	32	33	29
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	5	5	7
Sublease income	0	0	0
Total lease cost	37	38	36
Southern Company Gas
Lease cost
Operating lease cost	15	19	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	$ 15	$ 19	$ 19