Revenues (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,490	$ 2,244
Leasing revenues	30	22
Total revenues	3,520	2,266
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,427	2,217
Total revenues	3,427	2,217
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	730	515
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	209	155
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	137	132
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	104	96
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	202	103
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	702	366
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	440	233
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	265	125
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	638	492
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 63	$ 27