LEASES - Major Categories of Lease Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Lessee, Lease, Description [Line Items]
Lease obligations	$ 1,788	$ 1,899
Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	98	81
Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	1,115	1,240
Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	25	26
Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	546	542
Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	51	60
Electric generating units(*)
Lessee, Lease, Description [Line Items]
Lease obligations	670	760
Electric generating units(*) | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	58	59
Electric generating units(*) | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	1,028	1,163
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	871	885
Real estate/land | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	4	4
Real estate/land | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	54	54
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	546	542
Real estate/land | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	28	36
Communication towers
Lessee, Lease, Description [Line Items]
Lease obligations	123	141
Communication towers | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	1	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	23
Railcars
Lessee, Lease, Description [Line Items]
Lease obligations	64	34
Railcars | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	32	12
Railcars | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	27	18
Railcars | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	5	3
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	60	79
Other | Alabama Power
Lessee, Lease, Description [Line Items]
Lease obligations	3	4
Other | Georgia Power
Lessee, Lease, Description [Line Items]
Lease obligations	2	1
Other | Mississippi Power
Lessee, Lease, Description [Line Items]
Lease obligations	18	21
Other | Southern Power
Lessee, Lease, Description [Line Items]
Lease obligations	0	0
Other | Southern Company Gas
Lessee, Lease, Description [Line Items]
Lease obligations	$ 0	$ 1