Leases - Costs Disclosure (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2019
Leases
Weighted average remaining lease term	3 years
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Average discount rate (as a percent)	1.20%			3.50%
Lease cost
Net operating lease costs	$ 1,706	$ 2,133	$ 2,260
Minimum
Leases
Remaining lease term	0 years
Maximum
Leases
Remaining lease term	8 years
Lease extension term	5 years
Cost of revenues
Lease cost
Operating lease cost	$ 1,552	1,974
Selling, general and administrative expense.
Lease cost
Operating lease cost	243	230
Interest and other income, net
Lease cost
Rental revenues	$ (89)	$ (71)