Income taxes (Reconciliation of Unrecognized Tax Benefits on Domestic and Foreign Tax Positions) (Details) - CAD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Reconciliation for unrecognized tax benefits on the Company's domestic and foreign tax positions | |||
| Gross unrecognized tax benefits at beginning of year | $ 41 | $ 46 | $ 52 |
| Increases for: | |||
| Tax positions related to the current year | 4 | 4 | 4 |
| Decrease for: | |||
| Tax positions related to prior years | (3) | (8) | (8) |
| Settlements | (1) | (1) | (2) |
| Gross unrecognized tax benefits at end of year | 41 | 41 | 46 |
| Adjustments to reflect tax treaties and other arrangements | (16) | (13) | (14) |
| Net unrecognized tax benefits at end of year | $ 25 | $ 28 | $ 32 |