Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation - Expense Related to Stock Options (Detail)

v3.19.1
Stock-based Compensation - Expense Related to Stock Options (Detail) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Stock-based compensation expense related to stock options $ 492 $ 425
Research and development    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Stock-based compensation expense related to stock options 158 108
Selling, general and administrative    
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]    
Stock-based compensation expense related to stock options $ 334 $ 317