Major commitments and contingencies (Contingencies) (Details) - Personal Injury and Other Claims Provision - CAD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Canada | |||
| Loss Contingency [Abstract] | |||
| Increase (decrease) to personal injury and other claims provision pursuant to the results of external actuarial studies | $ 1 | $ (4) | $ 11 |
| Loss Contingency Accrual [Roll Forward] | |||
| Beginning of year | 165 | 180 | 168 |
| Accruals and other | 71 | 41 | 44 |
| Payments | (38) | (56) | (32) |
| End of year | 198 | 165 | 180 |
| Current portion - End of year | 45 | 29 | 24 |
| U.S. | |||
| Loss Contingency [Abstract] | |||
| Increase (decrease) to personal injury and other claims provision pursuant to the results of external actuarial studies | 7 | 13 | 2 |
| Loss Contingency Accrual [Roll Forward] | |||
| Beginning of year | 119 | 131 | 128 |
| Accruals and other | 36 | 43 | 34 |
| Payments | (39) | (65) | (28) |
| Foreign exchange | (4) | 10 | (3) |
| End of year | 112 | 119 | 131 |
| Current portion - End of year | $ 26 | $ 18 | $ 27 |