Investment and other income - Gains and Losses on Asset Sales (Detail) - CAD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Other Income and Expenses [Abstract] | ||||
| Proceeds from asset sales | $ 58 | $ 2 | $ 67 | $ 13 |
| Book value of asset sales | 2 | 1 | 3 | 2 |
| Gain (loss) on asset sales, before-tax | 56 | 1 | 64 | 11 |
| Gain (loss) on asset sales, after-tax | $ 49 | $ 1 | $ 56 | $ 10 |