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Stock Plans - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Jul. 31, 2014
Dec. 31, 2019
Dec. 31, 2018
Oct. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Total intrinsic value of stock options exercised   $ 10,700,000 $ 8,200,000  
Weighted-average fair values of options granted   $ 5.04 $ 4.15  
Unrecognized stock-based compensation expense related to awards   $ 20,700,000    
Unrecognized stock-based compensation, weighted-average period   2 years 9 months 18 days    
One time share based payment charge related to cancellation of unvested stock option of CEO and directors   $ 1,200,000 $ 4,100,000  
Plans [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock shares authorized for issuance   24,372,087    
Shares available for future grants   4,369,053    
Restricted Stock Units [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Unrecognized stock-based compensation, weighted-average period   1 year 6 months    
Weighted-average grant date fair value of RSUs granted   $ 3.95 $ 5.94  
Total fair values of RSUs vested   $ 3,400,000 $ 2,700,000  
Unrecognized compensation cost   $ 3,000,000    
Restricted Stock Units [Member] | Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Awards granted to employees and non-employees vesting period   4 years    
Restricted Stock Units [Member] | Minimum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Awards granted to employees and non-employees vesting period   2 years    
2014 Equity Incentive Award Plan [Member]        
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 [Member] | Stock Options and Restricted Stock Units [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock shares available for future grant       600,000
2014 Plan And Inducement Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock options granted description   Stock options under the 2014 Plan and the Inducement Plan may be granted for periods of up to 10 years and at prices no less than 100% of the estimated fair value of the shares on the date of grant as determined by the board of directors, provided, however, that the exercise price of an ISO and NSO granted to a 10% stockholder may not be less than 110% of the estimated fair value of the shares on the date of grant.    
Awards granted to employees and non-employees vesting period   4 years    
2014 Plan And Inducement Plan [Member] | Maximum [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock options granted period   10 years    
2014 Employee Stock Purchase Plan [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock shares available for future grant 208,833      
Shares available for future grants   1,875,022    
Unrecognized compensation cost   $ 222,000    
Percentage increase in shares issued 1.00%      
Common stock, shares issued   86,405