Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Summarizes Fortress warrant activities (Detail)

v3.19.1
Stockholders' Equity - Summarizes Fortress warrant activities (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Subsidiary or Equity Method Investee [Line Items]      
Number of shares, Granted 490,000 1,128,750  
Warrant [Member]      
Subsidiary or Equity Method Investee [Line Items]      
Number of shares, Outstanding 2,774,189 2,263,453  
Number of shares, Granted   816,180  
Number of shares, Forfeited (20,000) (305,444)  
Number of shares, Outstanding 2,754,189 2,774,189 2,263,453
Number of shares, Exercisable 849,189    
Weighted average exercise price, Outstanding $ 3.30 $ 3.62  
Weighted average exercise price, Granted   3.84  
Weighted average exercise price, Forfeited 5.72 7.07  
Weighted average exercise price, Outstanding 3.28 $ 3.30 $ 3.62
Weighted average exercise price, Exercisable $ 3.92    
Total weighted average instrinsic value, Outstanding $ 2,204,530 $ 79,800  
Total weighted average intrinsic value, Granted   260,380  
Total weighted average intrinsic value, Forfeited 0 0  
Total weighted average instrinsic value, Outstanding 0 $ 2,204,530 $ 79,800
Total weighted average intrinsic value, Exercisable $ 0    
Weighted average remaining contractual life (years), Outstanding 3 years 5 months 26 days 4 years 5 months 19 days 4 years 8 months 26 days
Weighted average remaining contractual life, Granted (years)   4 years 10 months 13 days  
Weighted average remaining contractual life, Exercisable (years) 3 years 1 month 17 days