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Share-Based Compensation - Additional Information (Detail) - USD ($)
shares in Thousands, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Compensation expense $ 2.5 $ 2.6 $ 2.9
Unrecognized compensation expense $ 4.9    
Shares expected to be surrendered by employees 161    
Restricted Stock | 2014 EIP      
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]      
Authorized shares available for issuance 2,600