Revenues - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 14,414	$ 12,442	$ 8,730
Leasing revenues	132	113	84
Total revenues	14,546	12,555	8,814
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	14,223	12,281	8,627
Total revenues	14,223	12,281	8,627
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,012	2,496	1,776
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	943	859	577
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	614	566	581
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	406	385	332
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	816	696	403
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,851	2,301	1,394
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,777	1,579	884
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,280	934	438
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,524	2,465	2,242
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 191	$ 161	$ 103