Quarterly report pursuant to Section 13 or 15(d)

Stock Option and Incentive Plans - Additional Information (Detail)

v3.19.2
Stock Option and Incentive Plans - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Dec. 31, 2015
Feb. 26, 2013
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Jul. 28, 2014
Apr. 29, 2014
Feb. 24, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares of common stock reserved pursuant to the plan     42,937,318   42,937,318   38,430,911      
Weighted average grant date fair value of options     $ 0.41 $ 1.63 $ 0.40 $ 1.45        
Unrecognized compensation cost related to unvested stock options     $ 3,200,000   $ 3,200,000          
Weighted average period of unvested stock options         2 years 9 months 29 days          
Employee Stock Options [Member]                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Compensation expense recognized     $ 369,927 $ 416,133 $ 693,701 $ 853,814        
Amended and Restated 2008 Equity Incentive Plan [Member]                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares of common stock reserved pursuant to the plan   1,571,428                
Termination of service, Period   2 years                
2008 Equity Incentive Plan [Member]                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares of common stock reserved pursuant to the plan                 2,357,142 1,857,142
Termination of service, Period   10 years                
2014 Omnibus Incentive Plan [Member]                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares of common stock reserved pursuant to the plan               571,429    
Number of additional shares increases of common stock reserved pursuant to the plan         9,696,859          
2014 Omnibus Incentive Plan [Member] | Maximum [Member]                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Annual increase of plan, percentage of common stock shares outstanding 4.00%