LEASES - Summary of Supplementary Balance Sheet Information (Details) - CAD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
|---|---|---|
| Leases [Abstract] | ||
| Other long-term assets (Note 12) | $ 47 | $ 55 |
| Accounts payable and other current liabilities (Note 13) | 14 | 14 |
| Other long-term liabilities (Note 14) | $ 29 | $ 41 |
| Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration] | Other assets (Note 12) | Other assets (Note 12) |
| Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration] | Accounts payable and other current liabilities (Note 13) | Accounts payable and other current liabilities (Note 13) |
| Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration] | Other long-term liabilities (Note 14) | Other long-term liabilities (Note 14) |