Segmented Information (Details) (CAD) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segmented Information [Abstract]
Approximate percentage of the Company's freight revenues from national accounts (in hundredths)	95.00%
Number of customers with greater than 10% of total revenues	0
Largest rail freight customer percentage of total rail freight revenues (in hundredths)	2.00%	2.00%	2.00%
Number of operating segments	1us-gaap_NumberOfOperatingSegments
Segment Reporting Information [Line Items]
Revenues	12,134us-gaap_Revenues	10,575us-gaap_Revenues	9,920us-gaap_Revenues
Net income	3,167us-gaap_NetIncomeLoss	2,612us-gaap_NetIncomeLoss	2,680us-gaap_NetIncomeLoss
Properties	28,514us-gaap_PropertyPlantAndEquipmentNet	26,227us-gaap_PropertyPlantAndEquipmentNet
Canada [Member]
Segment Reporting Information [Line Items]
Revenues	8,108	7,149	6,770
Net income	2,249	1,762	1,972
Properties	15,798	15,056
U.S. [Member]
Segment Reporting Information [Line Items]
Revenues	4,026	3,426	3,150
Net income	918	850	708
Properties	12,716	11,171

Percent of entity's total rail freight revenue provided by the largest rail freight customer.

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- Definition

Number of company's customers that represent 10% or more of total revenues

+ References

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

+ References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

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.

+ References

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- Definition

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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- Definition

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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