Revenues (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,768	$ 3,490
Leasing revenues	27	30
Total revenues	3,795	3,520
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,727	3,427
Total revenues	3,727	3,427
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	788	730
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	257	209
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	156	137
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	114	104
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	217	202
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	758	702
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	448	440
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	315	265
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	674	638
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 41	$ 63