Stock-based compensation - Schedule of Company's Stock Option Activity (Details) - $ / shares	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Options, Outstanding	3,287,257	2,485,650
Number of Options, Granted	1,585,147	1,460,520	2,485,650
Number of Options, Exercised	(301,486)	(535,363)
Number of Options, Cancelled	(299,134)	(123,550)
Number of Options, Outstanding	4,271,784	3,287,257	2,485,650
Number of Options, Exercisable	1,234,933
Number of Options, Vested and expected to vest	4,271,784
Weighted-Average Exercise Price, Outstanding	$ 7.65	$ 2.84
Weighted-Average Exercise Price, Granted	40.85	13.75	$ 2.84
Weighted-Average Exercise Price, Exercised	4.46	2.84
Weighted-Average Exercise Price, Cancelled	21.79	3.96
Weighted-Average Exercise Price, Outstanding	19.20	$ 7.65	$ 2.84
Weighted-Average Exercise Price, Exercisable	6.13
Weighted-Average Exercise Price, Vested and expected to vest	$ 19.20
Weighted-Average Remaining Contractual Term, Granted			9 years 3 months
Weighted-Average Remaining Contractual Term, Outstanding		8 years 9 months 25 days	9 years 3 months
Weighted-Average Remaining Contractual Term, Exercisable	7 years 7 months 9 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	8 years 3 months 21 days

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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Gross number of share options (or share units) granted during the period.

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Number of options outstanding, including both vested and non-vested options.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of fully vested and expected to vest options outstanding that can be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for fully vested and expected to vest exercisable or convertible options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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Number of share options (or share units) exercised during the current period.

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