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Derivatives - Schedule of Pre-Tax Effects of Hedging on AOCI (Details) - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2026
Mar. 31, 2025
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI $ (3) $ 20
Cash Flow Hedging | Energy-related derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI 10 19
Cash Flow Hedging | Interest rate derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI 0 (2)
Cash Flow Hedging | Foreign currency derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI (12) 19
Fair Value Hedging | Foreign currency derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Amount excluded from effectiveness testing recognized in earnings (1) (16)
GEORGIA POWER CO | Cash Flow Hedging | Interest rate derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI 0 (2)
SOUTHERN POWER CO    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI (10) 22
SOUTHERN POWER CO | Cash Flow Hedging | Energy-related derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI 2 3
SOUTHERN POWER CO | Cash Flow Hedging | Foreign currency derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI (12) 19
SOUTHERN Co GAS | Cash Flow Hedging | Energy-related derivatives    
Derivative Instruments, Gain (Loss) [Line Items]    
Gain (Loss) From Derivatives Recognized in OCI $ 8 $ 16