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Share-based compensation - Share Options - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Oct. 31, 2021	Mar. 05, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized	7,369,767		7,369,767		7,345	4,140,945
Weighted-average grant-date fair value of options granted			$ 82.21	$ 34.91
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation expense	$ 7,175	$ 5,363	$ 19,951	$ 15,718
Unrecognized compensation expense related to unvested share options granted	$ 93,248		$ 93,248
Recognized over a weighted-average period			1 year 4 months 20 days
Management, Employees and Individual Advisors \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted			553,198	1,059,431
Exercise price of options			$ 180.00
Options granted contractual term			10 years	10 years
Vesting period			5 years
Management, Employees and Individual Advisors \| Vesting anniversary year after the grant date \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage			20.00%
Management, Employees and Individual Advisors \| Minimum \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of options				$ 44.94
Vesting period			3 years
Management, Employees and Individual Advisors \| Minimum \| Vesting anniversary year after the grant date \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage				20.00%
Management, Employees and Individual Advisors \| Maximum \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of options				$ 82.50
Vesting period			5 years
Management, Employees and Individual Advisors \| Maximum \| Vesting anniversary year after the grant date \| Two Thousand Seventeen Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option vesting percentage				33.30%