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Share-Based Compensation - Additional Information (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Common shares available for issuance under share-based compensation plan (shares) 1,100,000      
Total share-based compensation expense $ 11,911 $ 12,042 $ 11,306  
Recognized tax benefits from share-based compensation expense 4,600 4,500 4,400  
Total intrinsic value of stock options exercised $ 0 $ 0 $ 200  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number 0 0 0 15,000
Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Unrecognized compensation would be recognized based on accelerated vesting provisions $ 900      
Restricted Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period (in years) 3 years      
Total unrecognized compensation cost related to nonvested awards $ 28,500      
Total unrecognized compensation cost related to nonvested awards, period for recognition 2 years 8 months 12 days      
Value of stock that vested during the period $ 11,900 $ 11,000 $ 5,800  
Restricted Stock | Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period (in years) 1 year      
Restricted Stock | Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period (in years) 5 years      
Performance Shares        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period (in years) 3 years      
Total unrecognized compensation cost related to nonvested awards $ 2,200      
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period (in years) 3 years      
Stock option grants in period (shares) 0 0 0  
Stock Options | Minimum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award expiration period, years 7 years      
Stock Options | Maximum        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Award expiration period, years 10 years