Annual report pursuant to Section 13 and 15(d)

Stock Plan and Stock-Based Compensation - Additional Information (Detail)

v3.10.0.1
Stock Plan and Stock-Based Compensation - Additional Information (Detail) - USD ($)
1 Months Ended 12 Months Ended
Jan. 01, 2019
Jul. 31, 2016
Sep. 30, 2013
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2013
Dec. 31, 2007
Jun. 30, 2014
Apr. 30, 2014
Jan. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Intrinsic value of options exercised       $ 4,900,000 $ 2,500,000 $ 0          
Fair value of options vested       7,000,000 3,900,000 2,200,000          
Unamortized employee and non-employee stock-based compensation expense       $ 16,600,000              
Unamortized employee and non-employee stock-based compensation expense recognized period       2 years 9 months 18 days              
Number of option granted to employees       2,167,272              
Clinical development expense recognized       $ 0 $ 200,000 200,000          
Share reserved for issue       6,991,570 5,482,938            
Stock-based compensation expense       $ 7,013,000 $ 4,920,000 2,473,000          
Stock options outstanding       5,593,132 4,356,441            
Options to purchase common stock, unvested       0              
Performance Option [Member] | Executives and Senior Officers [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Number of option granted to employees   327,000                  
Scientific Advisors and Consultants [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, expiration period       10 years              
Share based compensation arrangement by share based payment award, award vesting period       48 months              
Stock-based compensation expense       $ 100,000 $ 100,000            
Issued warrants to purchase common stock       10,000 15,000            
Options to purchase common stock, unvested       22,793              
Incentive award issued       2,335              
Incentive awards outstanding, vested       2,335              
2013 Equity Incentive Plan [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, expiration period     10 years                
Share based compensation arrangement percentage increase in share reserved     5.00%                
Shares available for grant       1,268,662              
2013 Equity Incentive Plan [Member] | Subsequent Event [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Increase in shares reserved for issuance 2,378,259                    
2013 Equity Incentive Plan [Member] | Incentive Stock Options for Employees and Directors [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, exercise price percentage     100.00%                
2013 Equity Incentive Plan [Member] | Nonqualified Options to Employees, Directors and Consultants [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, exercise price percentage     85.00%                
2013 Equity Incentive Plan [Member] | Restricted Stock [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, exercise price percentage     85.00%                
Share based compensation arrangement by share based payment award, award vesting period     4 years                
2013 Equity Incentive Plan [Member] | Stock Options to 10% Stockholders [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, exercise price percentage               110.00%      
Share based compensation arrangement by share based payment award, award vesting period               5 years      
Incentive Awards [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Share based compensation arrangement by share based payment award, expiration period             10 years        
Share based compensation arrangement by share based payment award, award vesting period             4 years        
Share reserved for issue             252,752   500,000 252,752 252,752
Exercisable weighted average price per share             $ 5.21     $ 5.21 $ 5.21
Stock option plan, Description       Vest monthly over four years effective from their grant date.              
Stock-based compensation expense         $ 300,000 $ 300,000          
Stock options outstanding       129,776 129,776            
Incentive Awards [Member] | First Tranche [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Incentive awards vested percentage             100.00%