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Income taxes - Narrative (Details) CAD in Thousands	12 Months Ended
	Dec. 31, 2017 CAD provincial_jurisdiction	Dec. 31, 2016 CAD provincial_jurisdiction
Income Tax Disclosure [Abstract]
Number of provincial jurisdictions | provincial_jurisdiction	1	1
Deferred tax assets, non-capital operating loss carryforwards	CAD 17,584
Non-capital losses for income tax purposes	65,126
Valuation allowance, amount	1,035	CAD 1,035
Operating loss carryforwards, not subject to expiration	CAD 7,664

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- Definition

Number of Provincial Income Taxing Jurisdictions

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- Definition

Operating Loss Carryforwards, Not Subject To Expiration

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- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards that are subject to expiration dates.

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32559-109319

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