Accounts receivable, net (Details) - CAD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 2,066	$ 1,976
Allowance for credit losses	(98)	(89)
Total accounts receivable, net	1,968	1,887
Freight
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	1,635	1,559
Allowance for credit losses	(75)	(63)
Total accounts receivable, net	1,560	1,496
Non-freight
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	431	417
Allowance for credit losses	(23)	(26)
Total accounts receivable, net	$ 408	$ 391