Stock Based Compensation Plans (Details) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Stock based compensation plans:        
Stock-based compensation expense $ 600,710 $ 294,812 $ 2,139,513 $ 798,860
Tax benefits from stock-based compensation expense $ 234,277 $ 114,977 $ 834,410 $ 311,555
Stock options
       
Stock based compensation plans:        
Grants in period, options     0 186,306
Assumptions utilized in the valuation for options granted:        
Dividend yield       0.00%
Risk-free interest rate, minimum       1.95%
Risk-free interest rate, maximum       3.37%
Weighted-average expected life       7 years 3 months 18 days
Volatility, minimum       35.00%
Volatility, maximum       35.20%
Restricted stock
       
Stock based compensation plans:        
Grants in period, other than options     454,487 192,750