Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Schedule Of Supplemental Cash Flow Information [Line Items] | ||
| Financing leases | $ 41 | $ 25 |
| Operating leases | 299 | 12 |
| Virginia Electric and Power Company | ||
| Schedule Of Supplemental Cash Flow Information [Line Items] | ||
| Financing leases | 35 | 22 |
| Operating leases | 297 | $ 7 |
| Modifications of operating leases | $ 94 | |