Accounts receivable, net (Details) - CAD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	$ 1,976	$ 1,057
Allowance for credit losses	(89)	(41)
Total accounts receivable, net	1,887	1,016
Freight
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	1,559	785
Allowance for credit losses	(63)	(27)
Total accounts receivable, net	1,496	758
Non-freight
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable	417	272
Allowance for credit losses	(26)	(14)
Total accounts receivable, net	$ 391	$ 258