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Share Plans - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Sep. 28, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation $ 39,600,000 $ 34,200,000 $ 33,000,000  
Fair value of options granted        
Weighted average grant date fair value of options granted $ 12.59 $ 9.74 $ 16.40  
Total intrinsic value of options exercised $ 34,300,000 $ 27,100,000 $ 20,800,000  
Unrecognized compensation cost related to stock options 9,800,000      
Cash received from option exercises 46,000,000 31,600,000 28,700,000  
Tax benefit realized for tax deductions from option exercises $ 7,800,000 5,500,000 4,800,000  
Stock Options        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 3 years      
Expiration period 10 years      
Restricted shares and restricted stock units        
Weighted average period to recognize compensation cost 2 years      
Restricted Stock [Member]        
Restricted shares and restricted stock units        
Unrecognized compensation cost related to restricted stock units $ 39,600,000      
Total fair value of shares vested 21,700,000 27,200,000 26,000,000  
Restricted Stock Units        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation 17,500,000 17,300,000 21,600,000  
Restricted shares and restricted stock units        
Tax benefit realized for tax deductions from option exercises $ 0   2,400,000  
Weighted average period to recognize compensation cost 2 years 9 months 18 days      
Equity Option [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation $ 10,500,000 10,400,000 11,400,000  
Stock Appreciation Rights (SARs)        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 3 years      
Performance Shares [Member]        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation $ 11,600,000 $ 6,500,000 $ 0  
Restricted shares and restricted stock units        
Unrecognized compensation cost related to restricted stock units 10,500,000      
Tax benefit realized for tax deductions from option exercises $ 0      
Weighted average period to recognize compensation cost 1 year 7 months 9 days      
Maximum | Restricted Stock Units        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Vesting period 3 years      
2012 Stock and Incentive Plan        
Share Incentive Plans        
Number of shares authorized for issuance       9,000,000.0