Commitments and contingencies - Components of lease expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Commitments and contingencies
Operating lease cost	$ 1,364	$ 924	$ 4,057	$ 2,866
Variable lease cost	566	410	2,017	1,005
Total lease cost	$ 1,930	$ 1,334	$ 6,074	$ 3,871
Weighted-average remaining operating lease term (years)	3 years 2 months 12 days	4 years 6 months	3 years 2 months 12 days	4 years 6 months
Weighted-average discount rate	7.94%	7.03%	7.94%	7.03%