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Stock Plans - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized compensation cost $ 11.1    
Weighted average period to recognize compensation cost 2 years 3 months 19 days    
Compensation cost on stock-based compensation plans $ 6.6 $ 6.1 $ 6.2
Tax benefit recognized from all stock-based employee compensation plans 1.5 2.0 2.0
Cash received from stock option exercises 0.1 1.7 1.8
Employee service share based compensation tax benefit realized from share based compensation plans $ 1.0 1.7 3.2
Omnibus Incentive 2016 Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Maximum grant of stock options, restricted stock, and restricted stock units to directors and employees 1,600,000    
Omnibus Incentive 2016 Plan [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of options outstanding and exercisable 17,000    
Aggregate intrinsic value of options exercisable $ 0.9    
Total intrinsic value of options exercised $ 0.1 $ 3.9 $ 1.8
Omnibus Incentive 2016 Plan [Member] | Restricted Stock Units [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted, Weighted Average Grant-Date Fair-Value $ 66.54 $ 47.71 $ 57.21
Fair value of restricted stock awards vested $ 10.2 $ 8.9 $ 14.0
Omnibus Incentive 2016 Plan [Member] | Restricted Stock Units [Member] | Employee [Member] | Minimum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period from the date of grant for restricted stock awards granted 1 year    
Omnibus Incentive 2016 Plan [Member] | Restricted Stock Units [Member] | Employee [Member] | Maximum [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period from the date of grant for restricted stock awards granted 4 years    
Omnibus Incentive 2016 Plan [Member] | Restricted Stock Units [Member] | Non Employee Director [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period from the date of grant for restricted stock awards granted 1 year