Segment Information - Schedule of Product Revenue from Customers by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$ 8,112	$ 7,628	$ 23,381	$ 21,268
China
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	6,968	6,485	19,806	18,713
South Korea
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	705	434	2,156	1,157
Taiwan
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	277	413	650	1,062
Other
Revenues From External Customers And Long Lived Assets [Line Items]
Revenue	$ 162	$ 296	$ 769	$ 336