Annual report pursuant to Section 13 and 15(d)

Common Stock - Summary of Share-Based Compensation Expense (Detail)

v3.19.1
Common Stock - Summary of Share-Based Compensation Expense (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total stock-based compensation $ 854 $ 348
Research and development [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total stock-based compensation 272 107
General and administrative [Member]    
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]    
Total stock-based compensation $ 582 $ 241