Segment Information and Foreign Operations - Segment and Geographical Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of operating segments | segment	1
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	$ 20,723	$ 20,208
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	100,300		$ 100,341
Reportable Geographical Components | Europe (primarily Germany)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	6,214	4,375
Reportable Geographical Components | Taiwan
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	5,177	3,008
Reportable Geographical Components | China
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	4,724	7,111
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	99,380		99,272
Reportable Geographical Components | North America (primarily the United States)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	1,918	2,738
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	920		$ 1,069
Reportable Geographical Components | Asia Pacific (excluding China, Taiwan, and Japan)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	1,356	1,184
Reportable Geographical Components | Japan
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	$ 1,334	$ 1,792