Income Taxes (Details) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Income Tax Disclosure [Abstract]        
Income before provision for income taxes $ 6,198,330 $ 5,370,565 $ 16,867,740 $ 13,519,806
Income tax expense $ (2,381,394) $ (1,991,064) $ (6,336,180) $ (5,003,592)
Effective tax rate 38.40% 37.10% 37.60% 37.00%