Revenues (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 2,244	$ 1,818
Leasing revenues	22	20
Total revenues	2,266	1,838
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,217	1,796
Total revenues	2,217	1,796
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	515	360
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	155	139
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	132	104
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	96	78
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	103	86
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	366	310
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	233	181
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	125	91
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	492	447
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 27	$ 22