Annual report pursuant to Section 13 and 15(d)

Stock Option and Purchase Plans (Details Textual)

v2.4.0.6
Stock Option and Purchase Plans (Details Textual) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share based payment award options exercisable period 10 years      
Options outstanding 1,267,730 1,384,538 1,586,860 1,560,158
Share price $ 22.88 $ 31.14 $ 16.60  
Weighted Average Fair Value of the Options Granted $ 11.91 $ 15.18 $ 8.12  
Stock Option and Purchase Plans (Textual) [Abstract]        
Total fair value of options that vested during the year $ 1,000,000 $ 600,000 $ 700,000  
The weighted average fair value of options vested $ 7.41 $ 4.25 $ 3.72  
Total compensation costs related to non-vested awards 2,800,000      
Weighted average period 2 years 4 months 24 days      
Director [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Period of Options granted 6 months      
Key Employee [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Period of Options granted 5 years      
Directors Stock Option Plan [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Period of Options granted 6 months      
Options available for future grant 136,296      
Share based payment award options exercisable period 10 years      
Options outstanding 228,252      
Stock Incentive Plan [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Period of Options granted 5 years      
Options available for future grant 486,030      
Share based payment award options exercisable period 10 years      
Options outstanding 1,039,478      
Employee Stock [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Common stock price to market value 85.00%      
Number of shares employees had subscribed to purchase 61,606      
Investment as percentage of cash compensation 20.00%      
Cash compensation limit $ 21,700      
Share price $ 22.76      
Weighted Average Fair Value of the Options Granted $ 5.98 $ 4.75 $ 3.30