Financial and derivative instruments - Summary of realized and unrealized gain or (loss) on derivative instruments (Detail) - CAD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Derivative Instruments and Hedging Activities Disclosure [Abstract] | ||||
| Revenues | $ 128 | $ 20 | $ 233 | $ 11 |