Stock-Based Compensation Included in Consolidated Statements of Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 2,482	$ 1,614	$ 1,459
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	234	201	165
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	321	198	242
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation	$ 1,927	$ 1,215	$ 1,052