Stock Incentive Plans - Summary of Expense Relating to Employee and Nonemployee Stock-Based Payment Awards from Stock Options and RSUs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation, Total expensed	$ 411	$ 137	$ 692	$ 185
Cost of testing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation, Total expensed	54	9	69	9
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation, Total expensed	89	21	136	22
Sales and marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation, Total expensed	36	8	56	9
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share based compensation, Total expensed	$ 232	$ 99	$ 431	$ 145