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Stock-Based Compensation - Additional Information (Detail)
$ / shares in Units, $ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
Installment
$ / shares
shares
Sep. 30, 2017
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock-based compensation | $ $ 0.6 $ 0.5 $ 1.8 $ 1.6
Number of installments of restricted shares | Installment     3  
Restricted stock award vesting rights     The directors’ restricted shares vest over one year.  
Restricted Stock [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized compensation expense of restricted stock | $ $ 3.8 $ 4.0 $ 3.8 $ 4.0
2005 Executive Incentive Compensation Plan [Member] | Restricted Stock [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock shares granted | shares     406,743  
Weighted average fair market value of restricted shares granted | $ / shares     $ 6.84  
Non-Employee Directors' Restricted Stock Plan [Member] | Restricted Stock [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted stock shares granted | shares     33,732  
Weighted average fair market value of restricted shares granted | $ / shares     $ 7.12  
Non-Employee Directors' Restricted Stock Plan [Member] | Restricted Stock [Member] | Minimum [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares, vesting period     1 year  
Cliff Vest [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares, vesting period     5 years