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Stock-Based Employee Compensation - Additional Information (Detail)
$ / shares in Units, $ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2017
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2017
USD ($)
Installment
$ / shares
shares
Jun. 30, 2016
USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Stock-based compensation | $ $ 0.6 $ 0.4 $ 1.1 $ 0.8
Number of installments of restricted shares | Installment     3  
Restricted stock award vesting rights     The directors’ restricted shares vest on the date of the 2018 Annual Meeting.  
Restricted Stock [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized compensation expense of restricted stock | $ $ 4.5 $ 3.0 $ 4.5 $ 3.0
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     397,461  
Fair market value of restricted shares granted | $ / shares     $ 6.63  
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     27,696  
Fair market value of restricted shares granted | $ / shares     $ 8.68  
Cliff Vest [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Restricted shares, vesting period     5 years