Investment and other income - Gains and Losses on Asset Sales (Detail) - CAD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Other Income and Expenses [Abstract] | ||||
| Proceeds from asset sales | $ (2) | $ 21 | $ 65 | $ 34 |
| Book value of asset sales | 3 | 43 | 6 | 45 |
| Gain (loss) on asset sales, before-tax | (5) | (22) | 59 | (11) |
| Gain (loss) on asset sales, after-tax | $ (4) | $ (24) | $ 52 | $ (14) |