Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Stock Plan and Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Stock-based compensation expense $ 7,013 $ 4,920 $ 2,473
Research and Development [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Stock-based compensation expense 2,760 1,301 995
General and Administrative [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Stock-based compensation expense $ 4,253 $ 3,619 $ 1,478