Revenue Recognition - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,752	$ 1,648
Leasing revenues	15	14
Total revenues	1,767	1,662
Freight [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,726	1,625
Freight [Member] \| Grain [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	380	357
Freight [Member] \| Coal [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	158	151
Freight [Member] \| Potash [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	114	112
Freight [Member] \| Fertilizer and sulphur [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	57	61
Freight [Member] \| Forest products [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	73	66
Freight [Member] \| Energy, chemicals and plastic [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	315	257
Freight [Member] \| Metals, minerals and consumer products [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	173	183
Freight [Member] \| Automotive [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	76	71
Freight [Member] \| Intermodal [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	380	367
Non-Freight [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 26	$ 23

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The total amount of revenue recognized for the period from operating leases, including minimum lease revenue, contingent revenue, percentage revenue and sublease revenue.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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