Segmented and geographic information - Geographic Information (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 8,814	$ 7,995	$ 7,710
Long-term assets excluding investment in Kansas City Southern, financial instruments, and pension assets	23,404	22,196	21,423
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	6,423	5,992	5,829
Long-term assets excluding investment in Kansas City Southern, financial instruments, and pension assets	15,462	14,922	14,258
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	2,391	2,003	1,881
Long-term assets excluding investment in Kansas City Southern, financial instruments, and pension assets	$ 7,942	$ 7,274	$ 7,165