Leases - Lease costs recognized (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lease costs
Operating lease costs	$ 2,660	$ 2,663
Total lease cost	2,660	2,663
Operating cash flows used for operating leases	$ 3,388	$ 2,108
Weighted average remaining lease term	8 years 7 months 6 days	9 years 9 months 18 days
Weighted average discount rate	9.73%	9.73%