Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.1
Stock Plan and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Stock-based compensation expense $ 2,342 $ 1,796
Research and Development [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Stock-based compensation expense 1,112 649
General and Administrative [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Stock-based compensation expense $ 1,230 $ 1,147