Share-based compensation - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Number of shares
Options, Beginning balance	11,990,781
Options, Granted	5,386,784
Options, Exercised	(381,992)
Options, Forfeited	(1,062,581)
Options, Expired	(237,184)
Options, Ending balance	15,695,808		11,990,781
Options, Exercisable	4,972,974
Weighted Average Exercise price
Beginning price	$ 10.02
Granted	10.19
Exercised	2.66
Forfeited	9.42
Expired	22.94
Ending price	10.09		$ 10.02
Exercisable	$ 7.69
Weighted average remaining contractual term
Weighted Average Remaining Contractual Term	8 years 8 months 23 days		8 years 8 months 8 days
Weighted Average Remaining Contractual Term, Exercisable	7 years 9 months 29 days
Intrinsic value, outstanding	$ 41,765		$ 34,209
Intrinsic value, exercisable	$ 25,837
Weighted average grant date fair value	$ 7.53	$ 11.47
Intrinsic value, exercised	$ 2,500	$ 8,100

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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 weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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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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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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

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

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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 price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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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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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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

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