LEASES - Major Categories of Lease Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Lease obligations	$ 1,899	$ 1,969
Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	81	124
Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	1,240	1,291
Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	26	28
Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	542	526
Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	60	70
Electric generating units(*)
Lessee, Lease, Description [Line Items]
Lease obligations	760	802
Electric generating units(*) | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	59	104
Electric generating units(*) | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	1,163	1,217
Electric generating units(*) | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Electric generating units(*) | Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Electric generating units(*) | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Real estate/land
Lessee, Lease, Description [Line Items]
Lease obligations	885	876
Real estate/land | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	4	3
Real estate/land | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	54	49
Real estate/land | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	2	2
Real estate/land | Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	542	526
Real estate/land | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	36	45
Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	141	156
Communication towers | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	2	2
Communication towers | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	4	4
Communication towers | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Communication towers | Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Communication towers | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	23	24
Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	34	32
Railcars | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	12	10
Railcars | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	18	20
Railcars | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	3	2
Railcars | Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Railcars | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Other
Lessee, Lease, Description [Line Items]
Lease obligations	79	103
Other | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	4	5
Other | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	1	1
Other | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	21	24
Other | Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Other | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	$ 1	$ 1