Employee Future Benefits - Narrative (Details) - CAD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Retirement Benefits [Abstract] | ||||
| Defined contribution plan cost recognized | $ 18 | $ 16 | $ 37 | $ 35 |