v3.26.1
Fair Value Measurements - NPC - Level 3 (Details) - NPC - 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 $ (41) $ (57)
Changes in fair value recognized in regulatory assets (14) (24)
Settlements 4 8
Ending balance $ (51) $ (73)