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Stock-based compensation - Textuals (Details) - CAD |  |  | 12 Months Ended
--- | --- | --- | ---
Jul. 01, 2014 | Sep. 22, 2010 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Shares exercised and settled during period |  |  |  |  | 385,880 | 295,230
Proceeds from options exercised |  |  |  | CAD 82,000 | CAD 2,807,000 | CAD 1,175,000
Share option plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Options outstanding, weighted average remaining life |  |  |  | 5 years 5 months | 6 years 1 month |
Fair value of options vested during the year |  |  |  | CAD 806,000 | CAD 983,000 | CAD 1,278,000
Options exercisable |  |  |  | 886,220 | 824,720 |
Options exercisable, Weighted average exercise price (in CAD per share) |  |  |  | CAD 6.52 | CAD 8.41 |
Total compensation costs related to non-vested options not yet recognized |  |  |  | CAD 684,000 | CAD 1,223,000 |
Options forfeited |  |  |  | 287,840 | 61,480 | 698,624
Shares exercised and settled during period | [1] |  |  | 30,080 | 385,880 | 295,230
Total intrinsic value of options exercised |  |  |  | CAD 16,000 | CAD 1,711,000 | CAD 524,000
Proceeds from options exercised |  |  |  | CAD 82,000 | CAD 1,348,000 | 1,175,000
Share option plan | Stock options |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total compensation costs related to non-vested awards not yet recognized, weighted average recognition period |  |  |  | 1 year 8 months | 2 years 6 months |
Senior executive stock option plan |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Stock options reclassified from equity to a long-term liability |  |  | 550,000 |  |  |
Shares exercised and settled during period |  |  |  |  | 291,800 |
Total intrinsic value of options exercised |  |  |  |  | CAD 935,000 | 0
Proceeds from options exercised |  |  |  |  | 1,459,000 | CAD 0
Senior executive stock option plan | Stock options |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Options forfeited |  |  |  | 258,200 |  |
Current portion of award obligation |  |  |  | CAD 0 | CAD 22,000 |
Liability classified restricted share unit plan | Restricted share units (RSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total compensation costs related to non-vested awards not yet recognized, weighted average recognition period |  |  |  | 3 months | 9 months |
Service period of award subsequent to year of grant |  |  |  | 2 years |  |
Award vesting period |  |  |  | 3 years |  |
Redeemed (units) |  |  |  | 277,707 | 350,271 | 154,330
Award units settled during the period |  |  |  | CAD 1,030,000 | CAD 2,678,000 | CAD 727,000
Fair market value (CAD per share) |  |  |  | CAD 2.42 | CAD 3.78 |
Total unrecognized compensation costs related to non-vested non-option share-based payment arrangements |  |  |  | CAD 61,000 | CAD 641,000 |
Liability classified restricted share unit plan | Restricted share units (RSUs) | Accrued liabilities |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Current portion of award obligation |  |  |  | 671,000 | 1,009,000 |
Liability classified restricted share unit plan | Restricted share units (RSUs) | Other long-term liabilities |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Non-current portion of award obligation |  |  |  | CAD 0 | CAD 770,000 |
Equity classified restricted share unit plan | Restricted share units (RSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total compensation costs related to non-vested awards not yet recognized, weighted average recognition period |  |  |  | 2 years 1 month | 2 years 3 months |
Redeemed (units) |  |  |  | 19,798 | 605 |
Total unrecognized compensation costs related to non-vested non-option share-based payment arrangements |  |  |  | CAD 1,877,000 | CAD 1,276,000 |
Performance restricted share unit plan | Performance restricted share units (PSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Award vesting period |  | 3 years |  |  |  |
July 2014 Grant | Performance restricted share units (PSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total compensation costs related to non-vested awards not yet recognized, weighted average recognition period |  |  |  | 1 year 6 months | 2 years 6 months |
Total unrecognized compensation costs related to non-vested non-option share-based payment arrangements |  |  |  | CAD 281,000 | CAD 468,000 |
July 2015 Grant | Performance restricted share units (PSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total compensation costs related to non-vested awards not yet recognized, weighted average recognition period |  |  |  | 2 years 6 months |  |
Total unrecognized compensation costs related to non-vested non-option share-based payment arrangements |  |  |  | CAD 1,211,000 | CAD 0 |
Deferred share unit plan | Deferred stock units (DSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Percentage of non-officer directors' fixed remuneration in the form of DDSUs (50% or more) |  |  |  | 50.00% |  |
Liability classified deferred stock unit plan | Deferred stock units (DSUs) |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Redeemed (units) |  |  |  | 173,317 | 63,886 | 179,831
Award units settled during the period |  |  |  | CAD 527,000 | CAD 557,000 | CAD 968,000
Fair market value (CAD per share) |  |  |  | CAD 2.42 | CAD 3.78 |
Total unrecognized compensation costs related to non-vested non-option share-based payment arrangements |  |  |  | CAD 0 |  |
Liability classified deferred stock unit plan | Deferred stock units (DSUs) | Accrued liabilities |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Current portion of award obligation |  |  |  | 0 | CAD 408,000 |
Liability classified deferred stock unit plan | Deferred stock units (DSUs) | Other long-term liabilities |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Non-current portion of award obligation |  |  |  | 2,246,000 | CAD 1,597,000 |
Pay out to executives |  |  |  | 445,000 |  |
Equity classified deferred stock unit plan | Deferred stock units, dividend equivalent rights |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |
Total unrecognized compensation costs related to non-vested non-option share-based payment arrangements |  |  |  | CAD 0 |  |
[1] | All stock options exercised resulted in new common shares being issued (note 17(a))

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