Commitments and contingencies - Components of lease expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Commitments and contingencies
Operating lease cost	$ 1,341	$ 1,326
Variable lease cost	781	648
Total lease cost	$ 2,122	$ 1,974
Weighted-average remaining operating lease term (years)	2 years 8 months 12 days	3 years 8 months 12 days
Weighted-average discount rate	7.90%	7.60%