Post-employment benefit plans - Interest Cost (Details) - CAD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2025 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Disclosure of defined benefit plans [line items] | ||||
| Total net return on post-employment benefit plans | $ 36 | $ 26 | $ 73 | $ 51 |
| DB pension | ||||
| Disclosure of defined benefit plans [line items] | ||||
| Total net return on post-employment benefit plans | 43 | 33 | 88 | 66 |
| OPEBs | ||||
| Disclosure of defined benefit plans [line items] | ||||
| Total net return on post-employment benefit plans | $ (7) | $ (7) | $ (15) | $ (15) |