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Shareholders' Equity - Additional Information (Detail) - USD ($)
$ / shares in Units, shares in Thousands, $ in Thousands
12 Months Ended 163 Months Ended
May. 07, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2015
May. 21, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Issuance of shares under stock purchase plan         9,511  
Total intrinsic value of options exercised   $ 31,000 $ 18,000 $ 24,000    
Total unrecognized share-based compensation cost   $ 93,000     $ 93,000  
Unrecognized share-based compensation cost, weighted average period   3 years 1 month 8 days        
Stock Option Plan 2015            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares authorized for grant           3,000
Grants, maximum number of shares per person   100        
Shares available for granting of awards   81     81  
Employee Stock Option Plan | Upper end            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Award vesting period   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  
Number of additional shares authorized 3,000          
Purchase price percentage of fair market value   85.00%        
Amount withheld employee stock purchase plan   $ 13,783     $ 13,783  
Weighted average fair value of award granted during the period   $ 10.45 $ 9.60 $ 9.43    
Directors' Restricted Stock Plan 2014            
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Shares authorized for grant 250          
Shares available for granting of awards   185     185  
Fair value of annual grant per participant of restricted stock awards   $ 200        
Unvested restricted shares   0     0  
Restricted shares granted   34        
Weighted average fair value of award granted during the period   $ 47.27        
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   180,000     180,000