Share-based compensation - Schedule of Option Activity (Details) - $ / shares	9 Months Ended	12 Months Ended
Sep. 30, 2025	Dec. 31, 2024
Weighted average strike price per share (in $ per share)
Beginning balance (in dollars per share)	$ 8.69
Granted (in dollars per share)	2.61
Forfeited (in dollars per share)	3.53
Expired (in dollars per share)	17.41
Exercised (in dollars per share)	2.18
Ending balance (in dollars per share)	$ 8.43	$ 8.69
Number of awards
Beginning balance (in shares)	10,697,288
Granted (in shares)	536,650
Forfeited (in shares)	(422,773)
Expired (in shares)	(302,625)
Exercised (in shares)	(146,213)
Ending balance (in shares)	10,362,327	10,697,288
Additional Disclosures
Weighted average remaining life in years	6 years 10 months 17 days	7 years 6 months 21 days

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

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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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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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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