| Share-based compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands | 12 Months Ended | ||
|---|---|---|---|
| Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | |
| Total share-based compensation expense included in the consolidated statements of operations | |||
| Total share-based compensation expense | $ 11,773 | $ 18,240 | $ 20,629 | 
| Research and development | |||
| Total share-based compensation expense included in the consolidated statements of operations | |||
| Total share-based compensation expense | 3,061 | 6,264 | 9,052 | 
| General and administrative | |||
| Total share-based compensation expense included in the consolidated statements of operations | |||
| Total share-based compensation expense | $ 8,712 | $ 11,976 | $ 11,577 | 
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- Definition Amount of expense for award under share-based payment arrangement. Excludes amount capitalized. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- References No definition available. 
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