Leases - Future minimum lease payments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Rent expense	$ 2,644	$ 2,160	$ 1,994
Operating leases
2021	2,772
2022	2,843
2023	2,928
2024	3,016
2025 and thereafter	3,888
Total lease payments	15,447
Present value adjustment	(3,854)
Present value of lease liabilities	11,593
Finance leases
2021	116
2022	84
2023	74
2024	18
2025 and thereafter	0
Total lease payments	292
Present value adjustment	(25)
Present value of lease liabilities	$ 267