Annual report pursuant to Section 13 and 15(d)

Stock Option and Purchase Plans (Detail)

v3.3.1.900
Stock Option and Purchase Plans (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award        
Period of options granted (as noted) 5 years      
Share price (in usd per share) $ 40.71 $ 48.10 $ 36.96  
The weighted average fair value of options vested (in usd per share) $ 12.48 $ 7.05 $ 4.50  
Total fair value of options that vested during the year $ 1,500,000 $ 1,200,000 $ 1,000,000  
Total compensation costs related to non-vested awards $ 4,900,000      
Weighted average period (in years) 2 years 5 months      
Options (in shares) 1,256,478 1,466,238 1,945,497 2,099,364
Weighted average fair value of options granted (in usd per share) $ 20.70 $ 22.25 $ 16.83  
Employee Stock        
Share-based Compensation Arrangement by Share-based Payment Award        
Share price (in usd per share) $ 28.82      
Common stock price to market value (percentage) 85.00%      
Cash compensation limit $ 21,250      
Number of shares employees had subscribed to purchase (in shares) 128,802      
Weighted average fair value of options granted (in usd per share) $ 7.97 $ 9.66 $ 6.75  
Director        
Share-based Compensation Arrangement by Share-based Payment Award        
Period of options granted (as noted) 6 months      
Key Employee        
Share-based Compensation Arrangement by Share-based Payment Award        
Period of options granted (as noted) 5 years      
Maximum        
Share-based Compensation Arrangement by Share-based Payment Award        
Stock option exercisable period (not exceeding, in years) 10 years      
Stock Incentive Plan        
Share-based Compensation Arrangement by Share-based Payment Award        
Stock option exercisable period (not exceeding, in years) 10 years      
Period of options granted (as noted) 5 years      
Options (in shares) 1,033,176      
Options available for future grant (in shares) 587,687      
Directors Stock Option Plan        
Share-based Compensation Arrangement by Share-based Payment Award        
Stock option exercisable period (not exceeding, in years) 10 years      
Period of options granted (as noted) 6 months      
Options (in shares) 223,302      
Options available for future grant (in shares) 169,816