Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Additional Information (Detail)

v3.20.1
Stockholders' Equity - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Aug. 02, 2018
Aug. 31, 2017
Aug. 31, 2019
May 31, 2017
Jul. 31, 2013
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Net proceeds from the issuance of common stock       $ 30,600,000   $ 0 $ 0 $ 30,610,000  
Payment for repurchase of common stock           $ 0 $ 0 $ 11,203,000  
Total remaining options available for future grant           3,951,000 844,000    
Stock options granted to purchase common stock           1,723,000 943,000 1,733,000  
Weighted-average fair value of options granted           $ 1.84 $ 3.93 $ 3.79  
Total intrinsic value of stock options exercised           $ 0 $ 600,000 $ 300,000  
Intrinsic value of options outstanding           16,000      
Intrinsic value of options exercisable           1,000      
Unrecognized compensation expense           $ 27,000      
Weighted-average vesting term           10 months 24 days      
Stock-based compensation           $ 4,200,000 $ 3,800,000 $ 4,100,000  
Employment Inducement Award [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Stock options granted to purchase common stock   525,000              
Restricted Stock Units (RSUs) [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Number of shares granted           1,600,000      
Unrecognized compensation expense           $ 2,100,000      
Weighted-average vesting term           7 months 6 days      
2006 Plan [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common stock reserved for issuance to employees, nonemployee directors and consultants           1,030,303      
2013 Plan [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common stock reserved for issuance to employees, nonemployee directors and consultants         1,000,000        
Stock option plans, maximum term of plan         10 years        
Stock option plans, remaining vesting period         3 years        
Percentage of outstanding shares of common stock         5.00%        
Total remaining options available for future grant           3,951,438      
2013 Plan [Member] | Tranche right [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Stock option plans, percentage of options vested         25.00%        
One-Time Option Exchange [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Stock options exchange description           The participants received one new RSU for every two stock options tendered for exchange.      
Number of stock options exchanged     3,200,375            
Additional stock compensation expense expected service term     1 year            
One-Time Option Exchange [Member] | Restricted Stock Units (RSUs) [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Stock option plans, remaining vesting period     1 year            
Number of shares granted     1,600,186            
Incremental value of the modifications     $ 100,000            
2013 Warrants [Member] | Convertible promissory notes [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Warrant expiration date                 May 30, 2018
2013 Warrants [Member] | Series B Preferred Stock [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Warrant exercisable to purchase shares                 1,124,026
2013 Warrants [Member] | Series B Preferred Stock [Member] | Convertible promissory notes [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Exercise price of warrant per share                 $ 0.90
Lender Warrants [Member] | Series B convertible preferred stock [Member] | Term Loan One [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Exercise price of warrant per share                 $ 0.90
Warrant issued                 111,112
Warrant expiration date                 Jul. 03, 2023
Sales Agreement with Stifel [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Number of shares sold under sales agreement           0      
Sales Agreement with Stifel [Member] | Maximum [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common stock, value of shares issued $ 35,000,000                
Percentage of commission of gross sales price per share 3.00%                
Common Stock [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common stock, shares issued               5,980,000  
Common stock issued           5,000 36,000 24,000  
Common Stock [Member] | 2013 Warrants [Member] | Convertible promissory notes [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Exercise price of warrant per share         $ 7.43        
Common Stock [Member] | Lender Warrants [Member] | Convertible promissory notes [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Exercise price of warrant per share         $ 7.43        
Warrants exercisable         13,468        
Common Stock [Member] | Stock Purchase Agreement with Advent [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Payment for repurchase of common stock       $ 11,200,000          
Shares repurchased and retired under stock purchase agreement       2,166,836          
Shares repurchased and retired price per share       $ 5.17          
Follow on Offering [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common stock, shares issued       5,980,000          
Common stock, price per share       $ 5.50          
Post IPO [Member] | Common Stock [Member] | 2013 Warrants [Member] | Convertible promissory notes [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Warrants exercisable         136,236        
Employee Stock Purchase Plan [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Lower fair market value of purchase price share         85.00%        
Outstanding liability           $ 0 $ 28,936 $ 16,367  
Employee Stock Purchase Plan [Member] | Maximum [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Employee stock purchase plan, employees contribution         20.00%        
Employee Stock Purchase Plan [Member] | Common Stock [Member]                  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                  
Common stock issued           5,365 36,296 24,303