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STOCKHOLDERS' EQUITY (Details)
12 Months Ended
Dec. 31, 2015
USD ($)
Installment
Director
$ / shares
shares
Dec. 31, 2014
USD ($)
$ / shares
shares
Dec. 31, 2013
USD ($)
$ / shares
shares
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total stock-based compensation expense | $ $ 105,782 $ 21,416 $ 111,636
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of board of directors to whom stock options granted | Director 2    
Stock-based compensation expense | $ $ 105,782 $ 21,416 111,636
Stock granted during period, value of stock options | $     $ 165,000
Assumptions used to estimate the fair values of the stock options granted [Abstract]      
Risk-free interest rate 1.41% 1.66% 1.21%
Expected volatility 39.00% 32.00% 35.00%
Expected life 6 years 3 months 5 years 5 years
Dividend yield 0.00% 0.00% 0.00%
Stock Options Activity [Roll Forward]      
Outstanding, beginning of period (in shares) | shares 759,958 1,167,000  
Grants (in shares) | shares 30,000 15,000 30,000
Exercised (in shares) | shares (227,958) (407,042)  
Forfeitures or expirations (in shares) | shares 0 (15,000) (15,000)
Outstanding, end of period (in shares) | shares 562,000 759,958 1,167,000
Vested and expected to vest (in shares) | shares 562,000    
Exercisable (in shares) | shares 504,500    
Weighted Average Exercise Price [Roll Forward]      
Outstanding at beginning of year (in dollars per share) $ 11.04 $ 9.03  
Grants (in dollars per share) 37.64 26.48  
Exercised (in dollars per share) 12.39 5.27  
Forfeitures or expirations (in dollars per share) 0 26.48  
Outstanding at end of year (in dollars per share) 11.91 $ 11.04 $ 9.03
Vested and expected to vest (in dollars per share) 11.91    
Exercisable (in dollars per share) $ 9.6    
Weighted Average Remaining Contractual Term [Roll Forward]      
Outstanding, beginning of period 2 years 6 months 4 days 3 years 1 month 13 days 3 years 7 months 24 days
Grants 10 years 10 years  
Exercised 0 years 0 years  
Forfeitures or expirations 0 years 0 years  
Vested and expected to vest 2 years 6 months 4 days    
Exercisable 1 year 11 months 19 days    
Aggregate Intrinsic Value [Roll Forward]      
Outstanding, beginning of period | $ $ 23,483,235 $ 15,420,965  
Grants (in dollars per share) $ 0 $ 0  
Exercised | $ $ 9,251,027 $ 11,559,689  
Forfeitures and expirations (in dollars per share) $ 0 $ 0  
Outstanding at end of period | $ $ 17,456,220 $ 23,483,235 $ 15,420,965
Vested and expected to vest | $ 7,456,220    
Exercisable | $ $ 16,833,170    
Stock options by exercise price [Abstract]      
Number of Shares Outstanding (in shares) | shares 562,000    
Weighted Average Life 2 years 6 months 4 days    
Weighted Average Exercise Price (in dollars per share) $ 11.91    
Number of Shares Exercisable (in shares) | shares 504,500    
Weighted Average Option Price (in dollars per share) $ 9.60    
Weighted Average Life 1 year 11 months 19 days    
Proceeds from stock option exercises | $ $ 2,823,983 2,146,821 30,000
Closing price of Company stock (in dollars per share) $ 42.97    
Unrecognized compensation cost | $ $ 0.4    
Weighted average period for recognition of unrecognized compensation cost 3 years 2 months 1 day    
Board of Directors [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock granted during period, value of stock options | $ $ 450,000 $ 123,000 $ 165,000
Stock Options Activity [Roll Forward]      
Grants (in shares) | shares 30,000 15,000 30,000
2001 Stock Option Plan [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Number of shares authorized for issuance (in shares) | shares 2,050,000    
Exercise price per share of common stock 100.00%    
Number of installments for options vest and become exercisable | Installment 4    
Options expiry period 10 years    
Number of shares available for grant (in shares) | shares 209,098    
2001 Stock Option Plan [Member] | Non-Employee [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock-based compensation expense | $ $ 105,782 $ 21,416 $ 79,049
2001 Stock Option Plan [Member] | Qualified Incentive Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Exercise price per share of common stock 110.00%    
Minimum ownership percentage for qualified incentive stock options 10.00%    
Options expiry period 5 years    
Research and Development [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total stock-based compensation expense | $ $ 0 0 92,249
General and Administrative [Member]      
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]      
Total stock-based compensation expense | $ $ 105,782 $ 21,416 $ 19,387
0.83-1.00 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 0.83    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 1.00    
Number of Shares Outstanding (in shares) | shares 225,000    
Weighted Average Life 4 months 28 days    
Weighted Average Exercise Price (in dollars per share) $ 0.91    
Number of Shares Exercisable (in shares) | shares 225,000    
Weighted Average Option Price (in dollars per share) $ 0.91    
Weighted Average Life 4 months 28 days    
4.00-5.50 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 4.00    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 5.50    
Number of Shares Outstanding (in shares) | shares 50,000    
Weighted Average Life 1 year 8 months 12 days    
Weighted Average Exercise Price (in dollars per share) $ 5.22    
Number of Shares Exercisable (in shares) | shares 50,000    
Weighted Average Option Price (in dollars per share) $ 5.22    
Weighted Average Life 1 year 8 months 12 days    
13.24-15.85 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 13.24    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 15.85    
Number of Shares Outstanding (in shares) | shares 65,000    
Weighted Average Life 4 years 4 months 20 days    
Weighted Average Exercise Price (in dollars per share) $ 14.50    
Number of Shares Exercisable (in shares) | shares 65,000    
Weighted Average Option Price (in dollars per share) $ 14.50    
Weighted Average Life 4 years 4 months 20 days    
17.00-21.00 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 17.00    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 21.00    
Number of Shares Outstanding (in shares) | shares 145,000    
Weighted Average Life 3 years 4 months 17 days    
Weighted Average Exercise Price (in dollars per share) $ 19.48    
Number of Shares Exercisable (in shares) | shares 137,500    
Weighted Average Option Price (in dollars per share) $ 19.57    
Weighted Average Life 3 years 1 month 20 days    
26.43-37.64 [Member]      
Stock options by exercise price [Abstract]      
Range of Options Exercise Prices, lower limit (in dollars per share) $ 26.43    
Range of Options Exercise Prices, upper limit (in dollars per share) $ 37.64    
Number of Shares Outstanding (in shares) | shares 77,000    
Weighted Average Life 5 years 11 months 23 days    
Weighted Average Exercise Price (in dollars per share) $ 31.95    
Number of Shares Exercisable (in shares) | shares 27,000    
Weighted Average Option Price (in dollars per share) $ 27.67    
Weighted Average Life 3 years 9 months 14 days