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Stock-based compensation - Stock-based compensation expenses (Details) - General and administrative expenses - CAD | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |
Stock-based compensation expenses | CAD 3,995,000 | CAD 6,030,000
Share option plan |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |
Stock-based compensation expenses | 326,000 | 587,000
Liability classified restricted share unit plan |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |
Stock-based compensation expenses | 0 | 52,000
Equity classified restricted share unit plan |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |
Stock-based compensation expenses | 1,293,000 | 1,384,000
Performance restricted share unit plan |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |
Stock-based compensation expenses | 1,306,000 | 820,000
Liability classified deferred stock unit plan |  |
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] |  |
Stock-based compensation expenses | CAD 1,070,000 | CAD 3,187,000

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- Definition Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
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