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Stock Plans - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Oct. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total intrinsic value of stock options exercised $ 0.1 $ 20.8  
Weighted-average fair values of options granted (in USD per share) $ 5.18 $ 13.39  
Unrecognized stock-based compensation expense related to awards $ 43.1    
Unrecognized stock-based compensation, weighted-average period 2 years 10 months 24 days    
One time share based payment charge related to cancellation of unvested stock option of CEO and directors $ 1.6 $ 0.3  
Common stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock shares authorized for issuance (in shares) 33,965,569    
Shares available for future grants (in shares) 5,717,148    
Options      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award price as a percentage of grant date fair value, minimum 100.00%    
Incentive Stock Options (ISOs) and Non-Qualified Stock Options (NSOs)      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award price as a percentage of grant date fair value, minimum 110.00%    
Significant stockholder threshold ownership percentage 10.00%    
Restricted stock units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares of performance units both performance and service vesting conditions (in shares) 2,585,000 105,000  
Unrecognized stock-based compensation, weighted-average period 1 year 9 months 18 days    
Granted (in USD per share) $ 3.90 $ 15.75  
Total fair values of RSUs vested $ 1.6 $ 2.7  
Unrecognized compensation cost $ 4.5    
Restricted stock units | Minimum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Awards granted to employees and non-employees vesting period 2 years    
Restricted stock units | Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Awards granted to employees and non-employees vesting period 4 years    
Performance Shares      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Shares of performance units both performance and service vesting conditions (in shares) 1,300,000    
2014 Equity Incentive Award Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of annual increase in number of shares available for future issuance 4.00%    
2017 Inducement Plan | Stock Options and Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock shares available for future grant (in shares)     600,000
2014 Plan And Inducement Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Awards granted to employees and non-employees vesting period 4 years    
2014 Plan And Inducement Plan | Maximum      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options granted period 10 years    
2014 Employee Stock Purchase Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common stock shares available for future grant (in shares) 208,833    
Shares available for future grants (in shares) 2,130,542    
Unrecognized compensation cost $ 1.9    
Percentage increase in shares issued 1.00%    
Common stock issued (in shares) 397,763