Investment and other income - Gains and Losses on Asset Sales (Detail) - CAD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Other Income and Expenses [Abstract] | ||||
| Proceeds from asset sales | $ 2 | $ 3 | $ 13 | $ 7 |
| Book value of asset sales | 1 | 2 | 2 | 4 |
| Gain (loss) on asset sales, before tax | 1 | 1 | 11 | 3 |
| Gain (loss) on asset sales, after tax | $ 1 | $ 1 | $ 10 | $ 3 |