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Share-Based Compensation - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Common shares available for issuance under share-based compensation plan (shares) 1,400,000    
Total share-based compensation expense $ 15.2 $ 16.0  
Recognized tax benefits from share-based compensation expense $ 4.0 4.1  
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 $ 18.1    
Total unrecognized compensation cost related to nonvested awards, period for recognition 1 year 10 months 24 days    
Value of stock that vested during the period $ 13.8 $ 19.5  
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 $ 1.7    
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