v3.26.1
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)