Segment Information and Foreign Operations - Segment and Geographical Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) segment	Jun. 30, 2019 USD ($)	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	$ 22,134	$ 24,797	$ 42,857	$ 45,005
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	103,753		103,753		$ 100,341
Reportable Geographical Components | China
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	7,753	9,642	12,477	16,753
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	102,964		102,964		99,272
Reportable Geographical Components | Taiwan
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	4,398	4,655	9,575	7,663
Reportable Geographical Components | Japan
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	1,698	1,510	3,032	3,302
Reportable Geographical Components | Asia Pacific (excluding China, Taiwan, and Japan)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	1,701	2,738	3,057	3,922
Reportable Geographical Components | Europe (primarily Germany)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	4,114	4,640	10,328	9,015
Reportable Geographical Components | North America (primarily the United States)
Net revenues reported for products shipped to customers in corresponding geographic region [Abstract]
Revenue	2,470	$ 1,612	4,388	$ 4,350
Long-lived assets by geographic region, net of depreciation:
Long-lived assets	$ 789		$ 789		$ 1,069