Revenues (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 3,140	$ 2,181	$ 5,384	$ 3,999
Leasing revenues	34	21	56	41
Total revenues	3,174	2,202	5,440	4,040
Freight
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	3,101	2,154	5,318	3,950
Total revenues	3,101	2,154	5,318	3,950
Grain
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	537	370	1,052	730
Coal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	219	163	374	302
Potash
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	144	171	276	275
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	89	85	185	163
Forest products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	187	104	290	190
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	575	340	941	650
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	440	228	673	409
Automotive
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	257	120	382	211
Intermodal
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	653	573	1,145	1,020
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenues from contracts with customers	$ 39	$ 27	$ 66	$ 49