v3.25.0.1
RETIREMENT BENEFITS - Regulatory Assets (Details) - USD ($)
$ in Millions
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets $ 7,041 $ 6,523  
Regulatory asset   66 $ 216
Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 2,356 2,720  
Regulatory asset 70 76 97
Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 6,139 5,090  
Regulatory asset     83
Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 59 90  
Regulatory asset 52 44 $ 36
Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets (2,252) (2,225)  
Pension plans      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 2,658 2,913  
Pension plans | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 741 821  
Pension plans | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 973 1,051  
Pension plans | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 144 152  
Pension plans | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 126 143  
Regulatory asset 155 173  
Other Postretirement Benefits Plan      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 189 203  
Other Postretirement Benefits Plan | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 45 48  
Other Postretirement Benefits Plan | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 64 74  
Other Postretirement Benefits Plan | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 9 (10)  
Other Postretirement Benefits Plan | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 84 68  
Regulatory asset 16 24  
Prior Service Cost | Pension plans      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 8 9  
Prior Service Cost | Pension plans | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 3 4  
Prior Service Cost | Pension plans | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 5 6  
Prior Service Cost | Pension plans | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 1 1  
Prior Service Cost | Pension plans | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets (4) (7)  
Prior Service Cost | Other Postretirement Benefits Plan      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 11 13  
Prior Service Cost | Other Postretirement Benefits Plan | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 3 4  
Prior Service Cost | Other Postretirement Benefits Plan | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 4 5  
Prior Service Cost | Other Postretirement Benefits Plan | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 1 1  
Prior Service Cost | Other Postretirement Benefits Plan | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Net Actuarial Gain (Loss) | Pension plans      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 2,650 2,904  
Net Actuarial Gain (Loss) | Pension plans | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 738 817  
Net Actuarial Gain (Loss) | Pension plans | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 968 1,045  
Net Actuarial Gain (Loss) | Pension plans | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 143 151  
Net Actuarial Gain (Loss) | Pension plans | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 91 100  
Net Actuarial Gain (Loss) | Other Postretirement Benefits Plan      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 200 216  
Net Actuarial Gain (Loss) | Other Postretirement Benefits Plan | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 48 52  
Net Actuarial Gain (Loss) | Other Postretirement Benefits Plan | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 68 79  
Net Actuarial Gain (Loss) | Other Postretirement Benefits Plan | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 10 11  
Net Actuarial Gain (Loss) | Other Postretirement Benefits Plan | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 71 64  
Regulatory Amortization | Pension plans      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Pension plans | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Pension plans | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Pension plans | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Pension plans | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 39 50  
Regulatory Amortization | Other Postretirement Benefits Plan      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Other Postretirement Benefits Plan | Alabama Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Other Postretirement Benefits Plan | Georgia Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Other Postretirement Benefits Plan | Mississippi Power      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets 0 0  
Regulatory Amortization | Other Postretirement Benefits Plan | Southern Company Gas      
Defined Benefit Plan Disclosure [Line Items]      
Net regulatory assets $ (13) $ (4)