Segment Information - Summary of Revenue by Product Type (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Product Information [Line Items]
Total Revenue	$ 5,346	$ 8,036	$ 21,362	$ 36,773
Core [Member]
Product Information [Line Items]
Total Revenue	1,824	4,183	10,962	25,111
Wafer [Member]
Product Information [Line Items]
Total Revenue	2,136	2,085	5,769	6,093
Optical [Member]
Product Information [Line Items]
Total Revenue	1,116	1,612	4,075	5,016
Research & Development [Member]
Product Information [Line Items]
Total Revenue	$ 270	$ 156	$ 556	$ 553