Significant Accounting Policies (Schedule of Supplemental Cash Flow Information) (Parenthetical) (Detail) - USD ($) $ in Millions |
9 Months Ended | |
|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Schedule Of Supplemental Cash Flow Information [Line Items] | ||
| Financing leases | $ 64 | $ 281 |
| Operating leases | 302 | 34 |
| Virginia Electric and Power Company | ||
| Schedule Of Supplemental Cash Flow Information [Line Items] | ||
| Financing leases | 54 | 62 |
| Operating leases | 300 | $ 255 |
| Modifications of operating leases | $ 94 | |