Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Lease cost
Total operating lease cost	$ 1,343	$ 1,318	$ 2,751	$ 2,496
Depreciation of leased assets	328	328	656	681
Interest on lease liabilities	1,274	1,299	2,553	2,602
Total finance lease cost	1,602	1,627	3,209	3,283
Total lease cost	2,945	2,945	5,960	5,779
Short-term lease and variable lease costs	400	300	900	500
Service
Lease cost
Total operating lease cost	644	624	1,283	1,174
Research and development
Lease cost
Total operating lease cost	122	128	252	209
Sales and marketing*
Lease cost
Total operating lease cost	376	346	755	678
General and administrative*
Lease cost
Total operating lease cost	$ 201	$ 220	$ 461	$ 435