Quarterly report pursuant to Section 13 or 15(d)

Stock Option and Incentive Plans - Additional Information (Detail)

v3.19.1
Stock Option and Incentive Plans - Additional Information (Detail) - USD ($)
3 Months Ended
Dec. 31, 2015
Feb. 26, 2013
Mar. 31, 2019
Mar. 31, 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     40,071,858   38,430,911      
Weighted average grant date fair value of options     $ 0.40 $ 1.44        
Unrecognized compensation cost related to unvested stock options     $ 2,400,000          
Weighted average period of unvested stock options     2 years 7 months 6 days          
Employee Stock Options [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Compensation expense recognized     $ 323,774 $ 437,681        
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%