Investment in KCS - Summarized Financial Information, Statement of Income (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Schedule of Equity Method Investments [Line Items]
Revenues	$ 1,838	$ 1,959
Total operating expenses	1,303	1,179
Operating income	535	780
Income before income tax expense	675	793
Net income	590	$ 602
KCS
Schedule of Equity Method Investments [Line Items]
Revenues	986
Total operating expenses	617
Operating income	369
Other	39
Income before income tax expense	330
Net income	$ 238