Investment in KCS - Summarized financial information (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Schedule of Equity Method Investments [Line Items]
Total revenues	$ 2,266	$ 1,838
Total operating expenses	1,437	1,303
Operating income	829	535
Income before income tax expense	963	675
Net income	800	590
KCS
Schedule of Equity Method Investments [Line Items]
Total revenues	1,187	986
Total operating expenses	779	617
Operating income	408	369
Less : Other	74	39
Income before income tax expense	334	330
Net income	$ 246	$ 238