Fair Value Measurements - SPPC - Level 3 (Details) - Commodity - SPPC - 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 | $ (11) | $ (13) |
| Changes in fair value recognized in regulatory assets | (4) | (7) |
| Settlements | 0 | 1 |
| Ending balance | $ (15) | $ (19) |