Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease cost
Total operating lease cost	$ 1,318	$ 1,207	$ 2,496	$ 2,433
Depreciation of leased assets	328	332	681	665
Interest on lease liabilities	1,299	1,311	2,602	2,541
Total finance lease cost	1,627	1,643	3,283	3,206
Total lease cost	2,945	2,850	5,779	5,639
Short-term lease and variable lease costs	300	200	500	400
Service
Lease cost
Total operating lease cost	624	583	1,174	1,180
Research and development
Lease cost
Total operating lease cost	128	86	209	152
Sales and marketing*
Lease cost
Total operating lease cost	346	345	678	699
General and administrative*
Lease cost
Total operating lease cost	$ 220	$ 193	$ 435	$ 402