Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Compensation - Fair value assumptions (Details)

v3.19.2
Stock-Based Compensation - Fair value assumptions (Details) - $ / shares
6 Months Ended
Jun. 30, 2019
Feb. 28, 2018
Stock-Based Compensation    
Authorized shares 3,442,313  
Fair value of grants per share   $ 6.88
Options    
Stock-Based Compensation    
Terms of award ten  
Vesting period 4 years  
Expected dividend yield (as a percent) 0.00%  
Options | Employees    
Stock-Based Compensation    
Expected stock price volatility, minimum (as a percent) 78.05%  
Expected stock price volatility, maximum (as a percent) 79.38%  
Risk-free rate of interest, minimum (as a percent) 2.11%  
Risk-free rate of interest, maximum (as a percent) 2.53%  
Options | Employees | Minimum    
Stock-Based Compensation    
Exercise price per share (in dollars per share) $ 7.91  
Fair value of grants per share $ 5.31  
Expected Term (years) 5 years  
Options | Employees | Maximum    
Stock-Based Compensation    
Exercise price per share (in dollars per share) $ 10.45  
Fair value of grants per share $ 7.61  
Expected Term (years) 7 years