Quarterly report pursuant to Section 13 or 15(d)

Stock Plans - Additional Information (Details)

v3.19.2
Stock Plans - Additional Information (Details) - USD ($)
1 Months Ended 6 Months Ended
Jan. 31, 2019
Jun. 30, 2019
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award      
Weighted-average period for recognizing non-vested stock option   1 year 9 months  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares 122,115    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit $ 21.00    
Increase In The Price In Respect Of Lower Range In Respect Of Shares Authorised Under Compensation Plan $ 1.55    
Employee Stock Option      
Share-based Compensation Arrangement by Share-based Payment Award      
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized   $ 700,000  
2015 Plan      
Share-based Compensation Arrangement by Share-based Payment Award      
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized 1,666,667   583,334
Stock Compensation Plan      
Share-based Compensation Arrangement by Share-based Payment Award      
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost   136,000  
Stock Compensation Plan | Research and development      
Share-based Compensation Arrangement by Share-based Payment Award      
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost   77,000  
Stock Compensation Plan | General and administrative      
Share-based Compensation Arrangement by Share-based Payment Award      
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost   $ 59,000