Fair Value Measurements - MEC - Level 3 (Details) - MEC - Commodity - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Fair Value, Assets (Liabilities), Net, Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | ||
| Beginning balance | $ (2) | $ (2) |
| Changes in fair value recognized in regulatory assets | (1) | 1 |
| Settlements | 2 | 2 |
| Ending balance | $ (1) | $ 1 |