Annual report pursuant to Section 13 and 15(d)

Stock Option and Purchase Plans (Detail)

v3.6.0.2
Stock Option and Purchase Plans (Detail) - USD ($)
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award        
Period of options granted (as noted) 5 years      
Share price (in usd per share) $ 33.84 $ 35.40 $ 41.83  
The weighted average fair value of options vested (in usd per share) $ 12.05 $ 10.85 $ 6.13  
Total fair value of options that vested during the year $ 1,400,000 $ 1,500,000 $ 1,200,000  
Total compensation costs related to non-vested awards $ 5,200,000      
Weighted average period (in years) 2 years 5 months      
Options outstanding (in shares) 1,338,273 1,444,954 1,686,178 2,237,325
Weighted average fair value of options granted (in usd per share) $ 16.85 $ 18.00 $ 19.35  
Employee Stock        
Share-based Compensation Arrangement by Share-based Payment Award        
Share price (in usd per share) $ 33.09      
Cash compensation limit $ 21,250      
Common stock price to market value (percentage) 85.00%      
Number of shares employees had subscribed to purchase (in shares) 108,995      
Weighted average fair value of options granted (in usd per share) $ 9.88 $ 6.93 $ 8.40  
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 outstanding (in shares) 1,117,799      
Options available for future grant (in shares) 616,752      
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 outstanding (in shares) 220,474      
Options available for future grant (in shares) 172,288      
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