Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Summarizes Fortress warrant activities (Detail)

v3.8.0.1
Stockholders' Equity - Summarizes Fortress warrant activities (Detail) - Warrant [Member] - USD ($)
$ / shares in Units, $ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Subsidiary or Equity Method Investee [Line Items]      
Number of shares, Outstanding 2,263,453 569,835  
Number of shares, Granted 816,180 1,880,000  
Number of shares, Expired   (161,382)  
Number of shares, Exercised [1]   (25,000)  
Number of shares, Forfeited (305,444)    
Number of shares, Outstanding 2,774,189 2,263,453 569,835
Number of shares, Exercisable 869,189    
Weighted average exercise price, Outstanding $ 3.62 $ 6.31  
Weighted average exercise price, Granted 3.84 3.00  
Weighted average exercise price, Expired   6.30  
Weighted average exercise price, Exercised [1]   1.37  
Weighted average exercise price, Forfeited 7.07    
Weighted average exercise price, Outstanding 3.30 $ 3.62 $ 6.31
Weighted average exercise price, Exercisable $ 3.96    
Total weighted average instrinsic value, Outstanding $ 79,800 $ 120,700  
Total weighted average intrinsic value, Granted 260,380 0  
Total weighted average intrinsic value, Exercised [1]   33,250  
Total weighted average intrinsic value, Forfeited 0    
Total weighted average instrinsic value, Outstanding 2,204,530 $ 79,800 $ 120,700
Total weighted average intrinsic value, Exercisable $ 318,580    
Weighted average remaining contractual life (years), Outstanding 4 years 5 months 19 days 4 years 8 months 26 days 1 year 10 months 2 days
Weighted average remaining contractual life, Granted (years) 4 years 10 months 13 days 5 years 7 months 24 days  
Weighted average remaining contractual life, Exercisable (years) 4 years 18 days 0 years [1]  
[1] cashless