Annual report pursuant to Section 13 and 15(d)

Stock Based Compensation - Additional Information (Details)

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Stock Based Compensation - Additional Information (Details) - USD ($)
1 Months Ended 12 Months Ended
Aug. 31, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock, reserved for future issuance   2,238,000 2,021,000  
Weighted average grant-date fair value of options granted   $ 4.93 $ 3.97 $ 6.02
Stock options vested aggregate intrinsic value   $ 2,300,000 $ 2,500,000 $ 3,600,000
Stock options expected to vest aggregate intrinsic value   300,000 1,000,000 1,500,000
Grant date fair value of shares vested   $ 2,100,000 2,800,000 300,000
Employee Stock Purchase Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Offering period of employee stock purchase plan   6 months    
Limited percentage of annual contribution   20.00%    
Percentage of discount and fair value of option   15.00%    
Proceeds from stock issued during period $ 97,000      
Number of stock issued during period 10,000      
Restricted Stock        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Total unrecognized compensation cost   $ 2,300,000 $ 2,800,000 $ 2,500,000
Total unrecognized compensation cost, period for recognition   3 years    
Restricted Stock Units        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Total unrecognized compensation cost   $ 600,000    
Total unrecognized compensation cost, period for recognition   2 years 8 months 12 days    
Restricted stock units, Grants   96,000    
Weighted average grant date fair value, Grants   $ 11.35    
Restricted stock units, vesting period description   shares vest equally on each of the annual anniversaries over a four-year period    
Restricted Stock Units | Employees        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Restricted stock units, Grants   81,000    
Weighted average grant date fair value, Grants   $ 11.46    
Restricted stock units, vesting period   4 years    
Non-Employee Board of Directors        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of stock option value awarded per year   $ 30,000    
Non-Employee Board of Directors | Restricted Stock Units        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of restricted stock units value awarded per year   30,000    
Board of Directors        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of stock option value awarded per year   45,000    
Board of Directors | Restricted Stock Units        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of restricted stock units value awarded per year   $ 45,000    
Restricted stock units, Grants   14,000 4,000  
Weighted average grant date fair value, Grants   $ 10.75 $ 12.62  
Restricted stock units, vesting period description   shares vest on the first anniversary of the grant date shares vest equally on each of the annual anniversaries over a three-year period.  
Restricted stock units, vesting period     3 years  
Minimum        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Service period for stock options granted to employees   1 year    
Maximum        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Service period for stock options granted to employees   4 years    
Maximum | Employee Stock Purchase Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Purchase price percentage of market value of common stock   85.00%    
Authorized for Grants under the 2016 Equity Incentive Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock, reserved for future issuance   401,000 463,000