Segment Information and Foreign Operations - Segment and Geographical Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 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	$ 83,256	$ 102,397	$ 98,673
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	100,341	82,280
China
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	99,272	81,835
North America (primarily the United States)
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	1,069	445
Reportable Geographical Components
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	83,256	102,397	98,673
Reportable Geographical Components | China
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	26,796	31,492	24,962
Reportable Geographical Components | Europe (primarily Germany)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	18,178	22,013	23,956
Reportable Geographical Components | Taiwan
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	16,204	20,078	18,279
Reportable Geographical Components | North America (primarily the United States)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	8,228	10,021	8,352
Reportable Geographical Components | Asia Pacific (excluding China, Taiwan, and Japan)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	7,592	8,488	9,866
Reportable Geographical Components | Japan
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	$ 6,258	$ 10,305	$ 13,258