Fair Value Measurements - NPC - Level 3 (Details) - NPC - Commodity - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ||||
| Beginning balance | $ (51) | $ (73) | $ (41) | $ (57) |
| Changes in fair value recognized in regulatory assets | 1 | (8) | (13) | (32) |
| Settlements | 1 | 3 | 5 | 11 |
| Ending balance | $ (49) | $ (78) | $ (49) | $ (78) |