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Stock-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Incentive Plan, common stock available for issuance 6,000,000    
Incentive Plan, options vesting period 3 years    
Incentive Plan, options maturity period 10 years    
Incentive Plan, weighted-average grant date fair value of stock options granted $ 12.70 $ 11.58 $ 12.72
Unrecognized compensation cost related to unvested option $ 6.3    
Fair value of options vested 6.0 $ 7.8 $ 9.8
Intrinsic value of stock options exercised 88.1 78.0 63.4
Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized pre-tax compensation cost $ 19.2    
Unrecognized compensation cost, weighted-average recognition period 1 year 8 months 12 days    
Fair value of performance share awards vested $ 16.4 $ 24.9 $ 31.1
Stock Option Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation cost, weighted-average recognition period 1 year 7 months 6 days    
Performance Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized pre-tax compensation cost $ 6.4    
Unrecognized compensation cost, weighted-average recognition period 1 year 6 months    
Fair value of performance share awards vested $ 6.0    
Director Awards      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock awards issued 16,471 19,695 22,654
Common stock issued to outside directors $ 57.37 $ 46.21 $ 40.01