PENSION AND OTHER POSTRETIREMENT BENEFITS - Amount Recognized in Excess of Accumulated Other Comprehensive Income (Details) - CAD ($) $ in Millions |
Dec. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|
| Canada | ||
| Pension and Other Postretirement Benefit Disclosures | ||
| Accumulated benefit obligation | $ 404 | $ 394 |
| Fair value of plan assets | 283 | 243 |
| Canada | OPEB | ||
| Pension and Other Postretirement Benefit Disclosures | ||
| Accumulated benefit obligation | 210 | 228 |
| Fair value of plan assets | 0 | 0 |
| Projected benefit obligation | 428 | 416 |
| Fair value of plan assets | 283 | 243 |
| US | ||
| Pension and Other Postretirement Benefit Disclosures | ||
| Accumulated benefit obligation | 107 | 99 |
| Fair value of plan assets | 0 | 0 |
| US | OPEB | ||
| Pension and Other Postretirement Benefit Disclosures | ||
| Accumulated benefit obligation | 100 | 78 |
| Fair value of plan assets | 88 | 63 |
| Projected benefit obligation | 107 | 99 |
| Fair value of plan assets | $ 0 | $ 0 |