Segment Information - Summary of Revenue by Product Type (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Product Information [Line Items]
Revenue	$ 4,287	$ 8,910
Core [Member]
Product Information [Line Items]
Revenue	441	5,109
Wafer [Member]
Product Information [Line Items]
Revenue	2,345	1,891
Optical [Member]
Product Information [Line Items]
Revenue	1,404	1,769
Research & Development [Member]
Product Information [Line Items]
Revenue	$ 97	$ 141