Quarterly report pursuant to Section 13 or 15(d)

Stock Option and Incentive Plans - Additional Information (Detail)

v3.8.0.1
Stock Option and Incentive Plans - Additional Information (Detail) - USD ($)
 3 Months Ended
Dec. 31, 2015
Feb. 26, 2013
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Jul. 28, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Number of shares of common stock reserved pursuant to the plan     43,742,709   42,470,254  
Weighted average grant date fair value of options     $ 1.44 $ 1.75    
Unrecognized compensation cost related to unvested stock options     $ 3,569,426      
Weighted average period of unvested stock options     3 years 26 days      
Employee Stock Options [Member]            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Compensation expense recognized     $ 437,681 $ 380,911    
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]            
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     6,520,477      
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%