Leases - Lease costs and other lease information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease costs
Operating lease cost	$ 568	$ 598	$ 1,191	$ 1,170
Variable lease cost	468	211	665	410
Short-term lease cost	107	260	202	465
Finance lease cost
Interest on lease liabilities	11	16	23	31
Amortization of right-of-use assets	29	29	58	58
Sublease Income	(52)	(68)	(118)	(139)
Net lease cost	1,131	1,046	2,021	1,995
Operating cash flows from operating leases	561	$ 597	1,179	$ 1,174
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 1,348		$ 1,531
Minimum
Finance lease cost
Initial or remaining lease term under operating lease	1 year		1 year
Initial or remaining lease term under finance lease	1 year		1 year