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Net income per common share - Reconciliation of denominator used for calculation of basic and diluted net income per common share (Details) - shares | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018
Earnings per share [abstract] |  |
Denominator for basic net income per common share (in shares) | 76,592,413 | 80,494,302
Effect of dilutive stock options (in shares) | 17,325 | 67,631
Effect of dilutive TSARS (in shares) | 82,756 | 327,592
Denominator for diluted net income per common share (in shares) | 76,692,494 | 80,889,525

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- Definition The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2019-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2019-en-r&anchor=para_70_b&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition The number of dilutive potential ordinary shares that relate to the assumed exercise of the entity's share options. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 33 -IssueDate 2019-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2019-en-r&anchor=para_70_b&doctype=Standard -URIDate 2019-03-27 + Details
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- References No definition available. + Details
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- Definition The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 33 -IssueDate 2019-01-01 -Paragraph 70 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=33&code=ifrs-tx-2019-en-r&anchor=para_70_b&doctype=Standard -URIDate 2019-03-27 + Details
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- Definition Dilutive Securities, Effect On Basic Earnings Per Share, Tandem Share Appreciation Rights + References No definition available. + Details
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