XML 40 R30.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock-Based Awards - Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total stock-based compensation expense $ 2,466 $ 2,001
Research and Development [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total stock-based compensation expense 1,572 856
General and Administrative [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Total stock-based compensation expense $ 894 $ 1,145