Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Schedule Of Supplemental Cash Flow Information [Line Items] | ||
| Financing leases | $ 25 | $ 51 |
| Operating leases | 12 | 145 |
| Virginia Electric and Power Company | ||
| Schedule Of Supplemental Cash Flow Information [Line Items] | ||
| Financing leases | 22 | 42 |
| Operating leases | $ 7 | $ 129 |