Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation - Additional Information (Detail)

v3.8.0.1
Stock-Based Compensation - Additional Information (Detail) - USD ($)
12 Months Ended
May 31, 2013
Sep. 18, 2003
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
May 02, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Common stock, issued     21,352,000 20,893,000    
Restricted Share Units            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock awards vesting periods     3 years      
Weighted-average period     2 years 8 months 12 days      
Unrecognized compensation expense     $ 1,700,000      
Number of Restricted Shares, Shares Granted     351,449      
Weighted Average Grant Date Fair Value Per Share, Shares Granted     $ 7.20      
Restricted shares vested, fair value     $ 1,600,000      
Restricted Stock            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Weighted-average period     1 year 10 months 25 days      
Unrecognized compensation expense     $ 200,000      
Number of Restricted Shares, Shares Granted       327,508 110,350  
Weighted Average Grant Date Fair Value Per Share, Shares Granted       $ 6.25 $ 13.30  
Restricted shares vested, fair value     $ 1,200,000 $ 1,300,000 $ 1,500,000  
2013 Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock awards vesting periods 3 years          
Common stock, issued     1,600,000     500,000
2013 Plan | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options exercise price, percentage 100.00%          
2013 Plan | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Grant Expiration Date 10 years          
2003 Plan            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock awards vesting periods   3 years        
Options, issued     0 0    
Options outstanding, intrinsic value     $ 0      
Unrecognized compensation expense     $ 100,000      
2003 Plan | Minimum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Stock options exercise price, percentage   100.00%        
2003 Plan | Maximum            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Grant Expiration Date   10 years        
2003 Plan | Stock Options            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Weighted-average period     1 year