Segment Information - Schedule of Product Revenue from Customers by Geographic Region (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$ 34,339	$ 32,027	$ 31,098
China
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	22,105	23,533	26,175
Taiwan
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	6,587	4,061	897
South Korea
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	4,660	3,414	2,685
Japan
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	610	908	1,310
Other
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$ 377	$ 111	$ 31