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Stock-based compensation - Schedule of RSU activity (Detail) - $ / shares | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Weighted Average Grant Date Fair Value |  |  |
Outstanding weighted average grant date fair value, beginning balance | $ 34.56 |  |
Outstanding weighted average grant date fair value, ending balance |  | $ 34.56 |
Restricted Share Units (RSUs) |  |  |
Number of Restricted Share Units |  |  |
Outstanding number of shares (Units), beginning balance | 860,308 | 1,261,706 | 1,528,999
Granted, number of shares (Units) | 466,702 | 296,332 | 470,939
Vested, number of shares (Units) | (501,273) | (640,212) | (672,025)
Forfeited, number of shares (Units) | (66,230) | (57,518) | (66,207)
Outstanding number of shares (Units), ending balance | 759,507 | 860,308 | 1,261,706
Expected to vest, number of shares (Units) | 654,594 | 762,877 | 1,149,286
Weighted Average Grant Date Fair Value |  |  |
Outstanding weighted average grant date fair value, beginning balance | $ 36.44 | $ 31.41 | $ 27.45
Granted, weighted average grant date fair value | 44.00 | 40.40 | 37.58
Vested, weighted average grant date fair value | 34.41 | 28.28 | 26.84
Forfeited, weighted average grant date fair value | 38.02 | 37.35 | 30.43
Outstanding weighted average grant date fair value, ending balance | $ 42.29 | $ 36.44 | $ 31.41
Net settlement on vesting of restricted share units (Note 18) (in shares) | 300,944 | 385,197 | 521,707
Restricted Share Units (RSUs) | Vested in 2019, excluding directors |  |  |
Number of Restricted Share Units |  |  |
Vested, number of shares (Units) |  |  | (637,933)
Restricted Share Units (RSUs) | Vested in 2019, directors |  |  |
Number of Restricted Share Units |  |  |
Vested, number of shares (Units) | (34,092) |  |
Restricted Share Units (RSUs) | Vested in 2020, excluding directors |  |  |
Number of Restricted Share Units |  |  |
Vested, number of shares (Units) |  | (590,699) |
Restricted Share Units (RSUs) | Vesting in 2020, directors |  |  |
Number of Restricted Share Units |  |  |
Vested, number of shares (Units) | (49,513) |  |
Restricted Share Units (RSUs) | Vested in 2021, excluding directors |  |  |
Number of Restricted Share Units |  |  |
Vested, number of shares (Units) | (461,640) |  |
Restricted Share Units (RSUs) | Vesting in 2021, directors |  |  |
Number of Restricted Share Units |  |  |
Vested, number of shares (Units) | (39,633) |  |

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- Definition As of the balance sheet date, the number of shares expected to be issued in future for awards (other than stock options) expected to vest. + References No definition available. + Details
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- Definition Number, after shares used to satisfy grantee's tax withholding obligation for award under share-based payment arrangement, of restricted shares issued. Excludes cash used to satisfy grantee's tax withholding obligation. + References No definition available. + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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