Segmented Information (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Number of operating segments	1
Approximate percentage of the Company's freight revenues from national accounts	95.00%
Revenues	CAD 13,041	CAD 12,037	CAD 12,611
Net income	5,484	3,640	3,538
Properties	CAD 34,189	33,755
Customer Concentration Risk [Member]
Segment Reporting Information [Line Items]
Concentration of risk	3.00%
Customer Concentration Risk [Member] \| Major Customer Accounted for More Than 10 Percent of Total Revenue [Member]
Segment Reporting Information [Line Items]
Number of Customers	0
Canada [Member]
Segment Reporting Information [Line Items]
Revenues	CAD 8,794	7,971	8,283
Net income	2,857	2,708	2,469
Properties	18,305	17,445
U.S. [Member]
Segment Reporting Information [Line Items]
Revenues	4,247	4,066	4,328
Net income	2,627	932	CAD 1,069
Properties	CAD 15,884	CAD 16,310

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Approximate percentage of company's freight revenues from national accounts.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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