Nature of the business (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Nature of the business
Accumulated deficit	$ 728,164	$ 515,770
Non-restricted cash and cash equivalents	$ 653,482	$ 143,351

Amount of accumulated undistributed earnings (deficit).

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Name:	us-gaap_RetainedEarningsAccumulatedDeficit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant