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Operating Revenue (Narrative) (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2024
Dec. 31, 2023
Revenues From Contract With Customer [Line Items]    
Revenue recognized from contract liability balances $ 45 $ 48
Other Current Liabilities and Other Deferred Credits and Other Liabilities    
Revenues From Contract With Customer [Line Items]    
Contract liability balances 52 47
Virginia Electric and Power Company    
Revenues From Contract With Customer [Line Items]    
Revenue recognized from contract liability balances 40 39
Virginia Electric and Power Company | Other Current Liabilities and Other Deferred Credits and Other Liabilities    
Revenues From Contract With Customer [Line Items]    
Contract liability balances $ 46 $ 40