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Shares - Net income per share (Details) - CAD ($) $ / shares in Units, $ in Thousands | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Apr. 30, 2020 | Apr. 06, 2020 | Mar. 23, 2020 | Mar. 15, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] |  |  |  |  |  |
Net income available to common shareholders | $ 49,208 | $ 36,878 |  |  |  |
Interest from convertible debentures (after tax) | 2,370 | 3,590 |  |  |  |
Diluted net income available to common shareholders | $ 51,578 | $ 40,468 |  |  |  |
Weighted average number of common shares (in shares) | 28,165,130 | 25,444,374 |  |  |  |
Weighted-average effect of dilutive securities |  |  |  |  |  |
Dilutive effect of treasury shares (in shares) | 1,949,717 | 1,898,645 |  |  |  |
Dilutive effect of stock options (in shares) | 90,741 | 255,378 |  |  |  |
Weighted average number of diluted common shares (in shares) | 32,300,824 | 32,843,211 |  |  |  |
Basic net income per share (in CAD per share) | $ 1.75 | $ 1.45 |  |  |  |
Diluted net income per share (in CAD per share) | $ 1.60 | $ 1.23 |  |  |  |
FIve Point Zero Percent Convertible Debentures |  |  |  |  |  |
Weighted-average effect of dilutive securities |  |  |  |  |  |
Dilutive effect of convertible debentures (in shares) | 2,095,236 | 1,647,487 |  |  |  |
Five Point Five Zero Percent Convertible Debentures |  |  |  |  |  |
Weighted-average effect of dilutive securities |  |  |  |  |  |
Dilutive effect of convertible debentures (in shares) | 0 | 3,597,327 |  |  |  |
Convertible Subordinated Debt | FIve Point Zero Percent Convertible Debentures |  |  |  |  |  |
Weighted-average effect of dilutive securities |  |  |  |  |  |
Interest rate | 5.00% | 5.00% |  |  |  |
Convertible Subordinated Debt | Five Point Five Zero Percent Convertible Debentures |  |  |  |  |  |
Weighted-average effect of dilutive securities |  |  |  |  |  |
Interest rate | 5.50% | 5.50% | 5.50% | 5.50% | 5.50% | 5.50%

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