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Stock-based Compensation Plans - Additional Information 2 (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Dec. 31, 2016
Equity Awards      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Granted 870,326 927,000  
Granted, weighted average grant date fair value $ 32.98 $ 28.04  
Vesting period 3 years    
Stock-based compensation expense $ 6.0 $ 5.8  
Restricted Stock Liability Awards      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Granted 66,078    
Granted, weighted average grant date fair value $ 32.67    
Stock-based compensation expense $ 2.7 $ 3.7  
Restricted Stock Liability Awards | Employees      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Granted 66,078 136,000  
Granted, weighted average grant date fair value $ 32.67 $ 28.40  
Vesting period 3 years 3 years  
Stock Appreciation Rights (SARs)      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Vesting period 3 years    
Number of stock option outstanding 907,723   1,003,600