Revenues (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,305	$ 2,292	$ 8,689	$ 6,291
Leasing revenues	34	20	90	61
Total revenues	3,339	2,312	8,779	6,352
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,266	2,264	8,584	6,214
Total revenues	3,266	2,264	8,584	6,214
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	600	391	1,652	1,121
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	229	156	603	458
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	133	170	409	445
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	91	81	276	244
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	199	109	489	299
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	643	360	1,584	1,010
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	455	246	1,128	655
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	266	111	648	322
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	650	640	1,795	1,660
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 39	$ 28	$ 105	$ 77