Revenues - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 12,442	$ 8,730	$ 7,916
Revenues from contracts with customers	113	84	79
Total revenues	12,555	8,814	7,995
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	12,281	8,627	7,816
Total revenues	12,281	8,627	7,816
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,496	1,776	1,684
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	859	577	625
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	566	581	463
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	385	332	305
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	696	403	348
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,301	1,394	1,563
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	1,579	884	728
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	934	438	376
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	2,465	2,242	1,724
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 161	$ 103	$ 100