Revenues (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,673	$ 3,577	$ 7,441	$ 7,067
Leasing revenues	26	26	53	56
Total revenues	3,699	3,603	7,494	7,123
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,629	3,534	7,356	6,961
Total revenues	3,629	3,534	7,356	6,961
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	743	665	1,531	1,395
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	256	236	513	445
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	167	180	323	317
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	98	103	212	207
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	195	203	412	405
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	712	695	1,470	1,397
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	444	464	892	904
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	330	358	645	623
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	684	630	1,358	1,268
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 44	$ 43	$ 85	$ 106