Revenues (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,503	$ 3,305	$ 10,570	$ 8,689
Leasing revenues	46	34	102	90
Total revenues	3,549	3,339	10,672	8,779
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,461	3,266	10,422	8,584
Total revenues	3,461	3,266	10,422	8,584
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	668	600	2,063	1,652
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	248	229	693	603
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	144	133	461	409
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	91	91	298	276
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	198	199	603	489
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	712	643	2,109	1,584
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	443	455	1,347	1,128
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	333	266	956	648
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	624	650	1,892	1,795
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 42	$ 39	$ 148	$ 105