Segment Information - Summary of Revenue by Geographic Region (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 8,912	$ 8,036	$ 14,469	$ 14,268	$ 11,536	$ 11,115	$ 10,555	$ 8,307	$ 45,685	$ 41,513	$ 67,243
China [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									19,857	14,844	3,839
Taiwan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									9,843	7,361	5,663
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									5,452	4,444	11,104
Korea [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									5,001	2,214	19,862
Japan [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									1,517	309	2,999
Australia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									716	10,368	12,494
France [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									13	122	8,482
Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									1,169	455	863
Germany [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									925	436	553
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									976	337	554
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 216	$ 623	$ 830