XML 143 R112.htm IDEA: XBRL DOCUMENT v3.25.3
Derivatives - Schedule of Pre-tax Effects of Unrealized Derivative Gains (Losses) (Details) - Energy-related derivatives - USD ($)
$ in Millions
Sep. 30, 2025
Dec. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) $ 8 $ (50)
Other regulatory assets, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (24) (61)
Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (1) (5)
Other regulatory liabilities, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 13 8
Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 20 8
ALABAMA POWER CO    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 6 (16)
ALABAMA POWER CO | Other regulatory assets, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (7) (23)
ALABAMA POWER CO | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (1) 0
ALABAMA POWER CO | Other regulatory liabilities, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 7 4
ALABAMA POWER CO | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 7 3
GEORGIA POWER CO    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 1 (22)
GEORGIA POWER CO | Other regulatory assets, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (8) (26)
GEORGIA POWER CO | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 0 0
GEORGIA POWER CO | Other regulatory liabilities, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 1 0
GEORGIA POWER CO | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 8 4
MISSISSIPPI POWER CO    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (3) (15)
MISSISSIPPI POWER CO | Other regulatory assets, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (8) (11)
MISSISSIPPI POWER CO | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 0 (5)
MISSISSIPPI POWER CO | Other regulatory liabilities, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 0 0
MISSISSIPPI POWER CO | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 5 1
SOUTHERN Co GAS    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 4 3
SOUTHERN Co GAS | Other regulatory assets, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) (1) (1)
SOUTHERN Co GAS | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 0 0
SOUTHERN Co GAS | Other regulatory liabilities, current    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) 5 4
SOUTHERN Co GAS | Other regulatory assets, deferred    
Derivative Instruments, Gain (Loss) [Line Items]    
Total energy-related derivative gains (losses) $ 0 $ 0