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Contingencies - Environmental Remediation (Details) - USD ($)
$ in Millions
Sep. 30, 2023
Dec. 31, 2022
GEORGIA POWER CO    
Loss Contingencies [Line Items]    
Environmental remediation liability, current and former sites $ 14 $ 15
SOUTHERN Co GAS    
Loss Contingencies [Line Items]    
Environmental remediation liability, current and former sites $ 234 $ 256