| Share-based compensation (Tables) | 6 Months Ended | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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| Jun. 30, 2024 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Share-based compensation | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Summary of share-based compensation expense included in the consolidated statements of operations | The following table shows the total share-based compensation expense included in the unaudited consolidated statements of operations (in thousands): 
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| Summary of all stock option activity |  
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| X | ||||||||||
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- References No definition available. 
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| X | ||||||||||
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- Definition Tabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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