Annual report pursuant to Section 13 and 15(d)

Stock Plans - Additional information (Details)

v3.20.1
Stock Plans - Additional information (Details) - USD ($)
1 Months Ended 12 Months Ended
Jan. 31, 2019
Jul. 31, 2002
Aug. 31, 2001
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Aug. 31, 2015
Feb. 28, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Weighted-average period for recognizing non-vested stock option       1 year 6 months        
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number       1,192,000 665,000      
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value       $ 1.64 $ 3.21      
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 [Line Items]                
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized       $ 300,000        
Common Stock [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares, Outstanding       57,379,000 13,010,000 3,534,000    
2002 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized   217,000            
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number       49,344        
Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Fair Market Value Of Common Stock For Calculating Exercise Price   100.00%            
2001 Non-Qualified Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized     53,031          
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number       12,246        
Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Fair Market Value Of Common Stock For Calculating Exercise Price     100.00%          
2015 Plan                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized             1,666,667  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number       577,879        
2015 Plan | Common Stock [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares, Outstanding       1,088,788        
2014 Plan [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized               75,758
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number       41,345        
Stock Compensation Plan                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost       $ 81,000        
Research and development | Stock Compensation Plan                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost       54,000        
General and administrative | Stock Compensation Plan                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Share-based Compensation Arrangement by Share-based Payment Award, Plan Modification, Incremental Compensation Cost       $ 27,000