Investment in Securities (Details Textual) (USD $)
9 Months Ended
Sep. 30, 2011
Sep. 30, 2012
Security
Dec. 31, 2011
Security
Investment in Securities (Textual) [Abstract]      
Proceeds from sales of available-for-sale securities $ 15,650,000    
Gross realized gains 2,800,000    
Gross realized losses 56,000    
Income tax expense (benefit) related to gross gains 1,100,000    
Income tax expense (benefit) related to gross losses (23,000)    
Security sales   22,765,000  
Number of corporate debt securities   9  
Number of debt securities at unrealized losses     0
Percentage of aggregate depreciation related to nine debt securities     0.80%
Available-for-sale securities   $ 22,765,000 $ 0