Quarterly report pursuant to Section 13 or 15(d)

Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail)

v3.10.0.1
Stock Plans and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Stock-based compensation expense $ 1,751 $ 1,840 $ 3,547 $ 3,118
Research and Development [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Stock-based compensation expense 655 268 1,304 628
General and Administrative [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Stock-based compensation expense $ 1,096 $ 1,572 $ 2,243 $ 2,490