Other long-term liabilities - Schedule of Other Long-Term Liabilities (Details) - CAD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Other Liabilities Disclosure [Abstract]
Operating lease liabilities, net of current portion (Note 19)	$ 254	$ 242
Provision for environmental remediation, net of current portion	231	200
Stock-based compensation liabilities, net of current portion	177	161
Deferred lease and license revenue, net of current portion	67	68
Deferred revenue, net of current portion (Note 4)	20	16
Other, net of current portion	118	110
Total other long-term liabilities	867	797
Aggregate provision for environmental remediation, including current portion	$ 257	$ 220
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]	Accounts payable and accrued liabilities (Note 15, 19), Total other long-term liabilities	Accounts payable and accrued liabilities (Note 15, 19), Total other long-term liabilities