Leases - Components of lease costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Leases [Abstract]
Operating lease expense	$ 613	$ 341	$ 1,085	$ 682
Variable lease expense	174	211	373	414
Short-term lease expense	3	3	5	11
Total lease expense	$ 790	$ 555	$ 1,463	$ 1,107