Financial Instruments - Estimated Fair Values of Derivative Financial Instruments Included in Risk Management Asset (Details) - CAD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
|
| Reconciliation Of Changes In Derivative Financial Assets (Liabilities), Net [Roll Forward] | ||
| Derivative financial asset (liability), net, beginning balance | $ 5 | $ 9 |
| Risk management activities | (68) | (6) |
| Foreign exchange | (1) | 1 |
| Other comprehensive income | (1) | 1 |
| Derivative financial asset (liability), net, ending balance | (65) | 5 |
| Less: current portion | (8) | 5 |
| Derivative (liability) asset | $ (57) | $ 0 |