Revenues - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 1,961	$ 1,734	$ 3,714	$ 3,382
Leasing revenues	16	16	30	30
Total revenues	1,977	1,750	3,744	3,412
Freight [Member]
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,931	1,709	3,657	3,334
Total revenues	1,931	1,709	3,657	3,334
Grain
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	422	372	802	729
Coal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	173	164	331	315
Potash
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	136	116	250	228
Fertilizers and sulphur
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	63	55	120	116
Forest products
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	78	69	151	135
Energy, chemicals and plastics
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	346	278	661	535
Metals, minerals and consumer products
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	205	204	378	387
Automotive
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	104	91	180	162
Intermodal
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	404	360	784	727
Non-freight
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	30	25	57	48
Total revenues	$ 46	$ 41	$ 87	$ 78

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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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