Revenues - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 8,730	$ 7,916	$ 7,648
Leasing revenues	84	79	62
Total revenues	8,814	7,995	7,710
Freight
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	8,627	7,816	7,541
Total revenues	8,627	7,816	7,541
Grain
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,776	1,684	1,829
Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	577	625	566
Potash
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	581	463	493
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	332	305	290
Forest products
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	403	348	328
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,394	1,563	1,519
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	884	728	629
Automotive
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	438	376	324
Intermodal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,242	1,724	1,563
Non-freight excluding leasing revenues
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 103	$ 100	$ 107