Share-based Compensation Plans - Schedule of Share-Based Compensation by Line Item in Consolidated Statements of Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 5,724	$ 6,267	$ 6,303
Stock options [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	1,391	2,753	3,429
Restricted Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	3,400	1,964	1,387
Stock purchase plan [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	933	1,550	1,487
Cost of sales [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	137	104	592
Sales and marketing [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	1,701	1,444	1,550
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	3,578	4,483	4,023
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share based compensation expense	$ 308	$ 236	$ 138