Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lease cost
Total operating lease cost	$ 1,298	$ 1,177	$ 3,795	$ 3,609
Depreciation of leased assets	328	332	1,009	997
Interest on lease liabilities	1,296	1,308	3,898	3,849
Total finance lease cost	1,624	1,640	4,907	4,846
Total lease cost	2,922	2,817	8,702	8,455
Short-term lease and variable lease costs	300	200	800	600
Service
Lease cost
Total operating lease cost	601	552	1,776	1,732
Research and development
Lease cost
Total operating lease cost	137	80	347	232
Sales and marketing*
Lease cost
Total operating lease cost	347	338	1,024	1,037
General and administrative*
Lease cost
Total operating lease cost	$ 213	$ 207	$ 648	$ 608