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Shareholders' Equity - Additional Information (Detail)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended 36 Months Ended 199 Months Ended
Dec. 31, 2018
USD ($)
$ / shares
shares
Dec. 31, 2017
USD ($)
$ / shares
shares
Dec. 31, 2016
USD ($)
$ / shares
Apr. 30, 2016
Dec. 31, 2018
USD ($)
shares
May 02, 2017
shares
May 07, 2014
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Issuance of shares under stock purchase plan         11,562    
Total intrinsic value of options exercised | $ $ 92,000 $ 55,000 $ 29,000        
Total unrecognized share-based compensation cost | $ $ 56,000       $ 56,000    
Unrecognized share-based compensation cost, weighted average period 1 year 7 months 6 days            
2017 Omnibus Incentive Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares authorized for grant           2,500  
Shares available for granting of awards 1,431       1,431    
2017 Omnibus Incentive Plan | Upper end              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period 3 years 3 years          
Restricted Stock Units (RSUs)              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Grants in Period 466            
Number of common stock issued per unit based award upon vesting 1            
Weighted average fair value of award granted during the period | $ / shares $ 69.58 $ 54.11          
Performance Shares              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Grants in Period 18 23          
Maximum Adjustment Factor 2            
Minimum Adjustment Factor 0.5            
Minimum Shares Issued 0            
Number of common stock issued per unit based award upon vesting 1            
Weighted average fair value of award granted during the period | $ / shares $ 69.58 $ 54.11          
Employee Stock Option Plan | Upper end              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period     3 years 5 years      
Maximum contractual term     10 years        
Employee Stock Purchase Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares authorized for grant 12,305       12,305    
Purchase price percentage of fair market value 85.00%            
Amount withheld employee stock purchase plan | $ $ 18,646       $ 18,646    
Weighted average fair value of award granted during the period | $ / shares $ 17.49 $ 11.69 $ 10.99        
Directors' Restricted Stock Plan 2014              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares authorized for grant             250
Grants in Period 25            
Shares available for granting of awards 81       81    
Fair value of annual grant per participant of restricted stock awards | $ $ 200            
Unvested restricted shares 0       0    
Weighted average fair value of award granted during the period | $ / shares $ 72.19            
Non-Discretionary Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Number of shares authorized for repurchase 40,000       40,000    
Discretionary Plan              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Expected common stock shares issued and outstanding 160,000       160,000