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Share-based compensation - Changes in other equity instruments (Details) - shares | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Deferred share units |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Number of outstanding units, beginning of period (in shares) | 89,766 | 209,092
Number of outstanding units granted (in shares) | 29,393 | 14,158
Number of outstanding units performance factor impact on redemption (in shares) | 0 | 0
Number of outstanding units granted in lieu of dividends (in shares) | 3,788 | 4,031
Number of outstanding units redeemed (in shares) | 0 | (137,515)
Number of outstanding units cancelled (in shares) | 0 | 0
Number of outstanding units, end of period (in shares) | 122,947 | 89,766
Restricted share units |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Number of outstanding units, beginning of period (in shares) | 83,168 | 17,361
Number of outstanding units granted (in shares) | 154,460 | 79,240
Number of outstanding units performance factor impact on redemption (in shares) | 0 | 0
Number of outstanding units granted in lieu of dividends (in shares) | 7,326 | 2,840
Number of outstanding units redeemed (in shares) | (7,713) | (15,428)
Number of outstanding units cancelled (in shares) | (8,369) | (845)
Number of outstanding units, end of period (in shares) | 228,872 | 83,168
Performance share units (PSU) Old Plan |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Number of outstanding units, beginning of period (in shares) | 303,445 | 579,778
Number of outstanding units granted (in shares) | 0 | 0
Number of outstanding units performance factor impact on redemption (in shares) | (117,674) | 132,215
Number of outstanding units granted in lieu of dividends (in shares) | 4,529 | 9,909
Number of outstanding units redeemed (in shares) | (39,612) | (396,635)
Number of outstanding units cancelled (in shares) | (3,887) | (21,822)
Number of outstanding units, end of period (in shares) | 146,801 | 303,445
Performance Share Units (PSU) New Plan |  |
Disclosure of terms and conditions of share-based payment arrangement [line items] |  |
Number of outstanding units, beginning of period (in shares) | 138,038 | 0
Number of outstanding units granted (in shares) | 301,090 | 134,930
Number of outstanding units performance factor impact on redemption (in shares) | 0 | 0
Number of outstanding units granted in lieu of dividends (in shares) | 13,597 | 4,464
Number of outstanding units redeemed (in shares) | (1,842) | 0
Number of outstanding units cancelled (in shares) | (7,713) | (1,356)
Number of outstanding units, end of period (in shares) | 443,170 | 138,038

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- Definition The number of other equity instruments (ie other than share options) granted in a share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 2 -IssueDate 2020-01-01 -Paragraph 47 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_47_b&doctype=Standard -URIDate 2020-01-01 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2020-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard -URIDate 2020-01-01 + Details
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- Definition The number of other equity instruments (ie other than share options) forfeited in a share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 2 -IssueDate 2020-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2020-en-r&anchor=para_45&doctype=Standard -URIDate 2020-01-01 + Details
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