Leases (Narrative) (Detail) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Virginia Electric and Power Company | ||||
| Leases Disclosure [Line Items] | ||||
| Lease agreement maturity period | 15 years | |||
| Other deferred charges and other assets of right-of-use asset | $ 273 | $ 273 | ||
| Operating lease liabilities | 273 | 273 | ||
| Virginia Electric and Power Company | Other Current Liabilities | ||||
| Leases Disclosure [Line Items] | ||||
| Operating lease liabilities | 9 | 9 | ||
| Virginia Electric and Power Company | Other Deferred Credits and Other Liabilities | ||||
| Leases Disclosure [Line Items] | ||||
| Operating lease liabilities | 264 | 264 | ||
| Power Purchase Arrangement | ||||
| Leases Disclosure [Line Items] | ||||
| Rental revenue | 5 | $ 5 | 9 | $ 9 |
| Depreciation expense | $ 3 | $ 4 | $ 7 | $ 5 |