Share-based compensation - Restricted Share Units (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Restricted shares
Total share-based compensation expense	$ 9,042	$ 10,198
Restricted ordinary shares \| 2020 Plan
Number of Shares Underlying RSUs
Unvested restricted ordinary shares at beginning	187,725
Granted	321,839
Vested	(56,988)
Unvested restricted ordinary shares at ending	452,576
Weighted Average Grant Date Fair Value
Weighted average grant date fair value unvested, Beginning Balance	$ 60.86
Granted	29.59
Vested	55.34
Weighted average grant date fair value unvested, Ending Balance	$ 39.32
Restricted shares
Fair value of employee restricted share awards vested	$ 1,600	2,100
Total share-based compensation expense	1,600	$ 2,800
Unrecognized compensation cost	$ 16,500
Weighted average Period	3 years 1 month 6 days

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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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).

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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).

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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://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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-Paragraph 2
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-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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.

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