Stock-Based Compensation - Schedule of Stock-Based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	$ 1,276	$ 1,131	$ 4,245	$ 4,058
Sales and Marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	302	230	853	784
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	276	265	1,036	1,008
General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Share-based compensation, total	$ 698	$ 636	$ 2,356	$ 2,266