Segment Information - Summary of Revenue by Geographic Region (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 4,287	$ 8,910
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,538	510
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	1,111	1,523
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	422	725
Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	412	215
Taiwan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	383	1,701
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	2	3,351
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 419	$ 885