v3.26.1
Credit Risk (Narrative) (Detail)
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
USD ($)
Counterparty
Jun. 30, 2025
Jun. 30, 2026
USD ($)
Counterparty
Jun. 30, 2025
Dec. 31, 2025
USD ($)
Concentration Risk and Guarantor Obligations [Line Items]          
Credit exposure     $ 832,000,000    
Number of counterparties | Counterparty 0   0    
Amount of exposure for single counterparty     $ 450,000,000    
Additional collateral to be posted if the credit related contingent features were triggered $ 42,000,000   42,000,000   $ 29,000,000
Collateral derivatives with credit-related contingent provision in a liability position 0   0   0
Aggregate fair value of all derivative instruments with credit contingent provisions that are in a liability position 42,000,000   42,000,000   29,000,000
Letter of credit as collateral posted for derivatives in liability position $ 0   0   0
Virginia Electric and Power Company          
Concentration Risk and Guarantor Obligations [Line Items]          
Credit exposure     $ 15,000,000    
Number of counterparties | Counterparty 0   0    
Amount of exposure for single counterparty     $ 7,000,000    
Additional collateral to be posted if the credit related contingent features were triggered $ 0   0   0
Collateral derivatives with credit-related contingent provision in a liability position 0   0   0
Aggregate fair value of all derivative instruments with credit contingent provisions that are in a liability position 0   0   0
Letter of credit as collateral posted for derivatives in liability position $ 0   $ 0   $ 0
Credit Concentration Risk | Investment Grade Counterparty | Virginia Electric and Power Company          
Concentration Risk and Guarantor Obligations [Line Items]          
Concentration risk, percentage (percentage)     81.00%    
Credit Concentration Risk | Investment Grade | Investment Grade Counterparty          
Concentration Risk and Guarantor Obligations [Line Items]          
Concentration risk, percentage (percentage)     99.00%    
Customer Concentration Risk | Total Operating Revenue | Virginia Electric and Power Company          
Concentration Risk and Guarantor Obligations [Line Items]          
Concentration risk, percentage (percentage) 12.00% 10.00% 13.00% 9.00%  
Customer Concentration Risk | Customer Receivables | Virginia Electric and Power Company          
Concentration Risk and Guarantor Obligations [Line Items]          
Concentration risk, percentage (percentage)     14.00%   10.00%