Consolidated Statement of Stockholders' Equity (Unaudited) - 6 months ended Jun. 30, 2016 - USD ($)
Total
Common Stock
Additional Paid-In Capital
Treasury Stock
Retained Earnings
Balance at beginning of period (in shares) at Dec. 31, 2015   29,765,525      
Balance at beginning of period at Dec. 31, 2015 $ 395,249,574 $ 2,979 $ 319,002,254 $ (784,829) $ 77,029,170
Treasury stock at beginning of period (in shares) at Dec. 31, 2015 (37,937)     (37,937)  
Increase (decrease) in stockholders' equity:          
Share compensation expense $ 9,109,921   9,109,921    
Exercise of stock options (in shares)   4,550      
Exercise of stock options 53,158   53,158    
Common stock issued for vested restricted stock (in shares)   611,562      
Common stock issued for vested restricted stock 0 $ 61 (61)    
Common stock issued for vested performance shares (in shares)   37,547      
Common stock issued for vested performance shares 0 $ 4 (4)    
Common shares withheld and retired to satisfy employee tax withholding obligations upon vesting of share-based awards (in shares)   (200,531)      
Common shares withheld and retired to satisfy employee tax withholding obligations upon vesting of share-based awards (4,627,486) $ (20) (4,627,466)    
Tax deficiency from exercise of stock options (1,164,520)   (1,164,520)    
Purchases of treasury stock (in shares)       (1,528,719)  
Purchases of treasury stock (32,314,708)     $ (32,314,708)  
Net income 2,193,380       2,193,380
Balance at end of period (in shares) at Jun. 30, 2016   30,218,653      
Balance at end of period at Jun. 30, 2016 $ 368,499,319 $ 3,024 $ 322,373,282 $ (33,099,537) $ 79,222,550
Treasury stock at end of period (in shares) at Jun. 30, 2016 (1,566,656)     (1,566,656)