v3.25.2
Fair Value Measurements (Narrative) (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Unrealized gains (losses) included in operating revenue in Level 3 fair value category $ (3,000,000) $ 2,000,000 $ 10,000,000 $ (6,000,000)
Virginia Electric and Power Company        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Unrealized gains (losses) included in operating revenue in Level 3 fair value category $ 0 $ 0 $ 0 $ 0