PENSION AND OTHER POSTRETIREMENT BENEFITS - Amount Recognized in Accumulated Other Comprehensive Income (Details) - CAD ($) $ in Millions |
Dec. 31, 2024 |
Dec. 31, 2023 |
|---|---|---|
| Canada | Pension | ||
| Amount included in AOCI | ||
| Net actuarial (gain)/loss | $ (122) | $ 51 |
| Prior service cost | 0 | 0 |
| Total amount recognized in AOCI | (122) | 51 |
| Canada | OPEB | ||
| Amount included in AOCI | ||
| Net actuarial (gain)/loss | (99) | (82) |
| Prior service cost | 0 | (1) |
| Total amount recognized in AOCI | (99) | (83) |
| US | Pension | ||
| Amount included in AOCI | ||
| Net actuarial (gain)/loss | (42) | 74 |
| Prior service cost | 5 | 1 |
| Total amount recognized in AOCI | (37) | 75 |
| US | OPEB | ||
| Amount included in AOCI | ||
| Net actuarial (gain)/loss | (103) | (96) |
| Prior service cost | (16) | (22) |
| Total amount recognized in AOCI | $ (119) | $ (118) |