Annual report pursuant to Section 13 and 15(d)

STOCK BASED COMPENSATION (Details 3)

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STOCK BASED COMPENSATION (Details 3) (USD $)
 12 Months Ended
Dec. 31, 2013
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Dec. 31, 2012
Dec. 31, 2011
STOCK-BASED COMPENSATION      
Number of homogenous groups for purposes of determining fair values of options 3    
Weighted-average assumptions relating to options granted      
Stock-based compensation expense recognized $ 7,166,000 $ 12,617,000 $ 13,168,000
Employee Stock Purchase Plan
      
Weighted-average assumptions relating to options granted      
Risk-free interest rate (as a percent) 0.20% 0.20% 0.30%
Expected term (in years) 1 year 4 months 24 days 1 year 2 months 12 days 1 year
Dividend yield (as a percent) 0.00% 0.00% 0.00%
Expected volatility (as a percent) 64.40% 47.40% 61.40%
Employee Stock Option Plans
      
STOCK-BASED COMPENSATION      
Contractual term of the option 10 years    
Weighted-average assumptions relating to options granted      
Risk-free interest rate (as a percent) 1.10% 0.90% 2.10%
Expected term (in years) 5 years 4 months 24 days 5 years 6 months 5 years 2 months 12 days
Dividend yield (as a percent) 0.00% 0.00% 0.00%
Expected volatility (as a percent) 72.20% 81.50% 84.20%
Total number of shares of common stock reserved for future issuance 24,577,963    
Shares Available For Grant      
Outstanding at the beginning of the period (in shares) 3,198,586 4,707,753 2,528,099
Authorized for grant (in shares) 7,775,000 600,000 4,350,000
Granted (in shares) (3,140,956) (2,149,266) (2,236,270)
Cancelled (in shares) 1,213,131 40,099 65,924
Outstanding at the end of the period (in shares) 9,045,761 3,198,586 4,707,753
Number of Shares Underlying Options      
Outstanding at the beginning of the period (in shares) 13,604,377 11,749,359 9,694,001
Granted (in shares) 3,140,956 2,149,266 2,236,270
Exercised (in shares) 0 (254,149) (114,988)
Cancelled (in shares) (1,213,131) (40,099) (65,924)
Outstanding at the end of the period (in shares) 15,532,202 13,604,377 11,749,359
Vested and expected to vest (in shares) 15,432,482    
Exercisable (in shares) 13,246,612 12,841,378 10,982,934
Weighted Average Exercise Price      
Outstanding at the beginning of the period (in dollars per share) $ 11.52 $ 12.07 $ 13.22
Granted (in dollars per share) $ 5.46 $ 8.13 $ 6.80
Exercised (in dollars per share)   $ 7.08 $ 6.67
Cancelled (in dollars per share) $ 8.26 $ 19.60 $ 10.95
Outstanding at the end of the period (in dollars per share) $ 10.55 $ 11.52 $ 12.07
Vested and expected to vest (in dollars per share) $ 10.58    
Exercisable (in dollars per share) $ 11.44 $ 11.75 $ 12.38
Weighted Average Remaining Contractual Term (in years)      
Outstanding at the end of the period 5 years 8 months 16 days    
Exercisable 5 years 1 month 13 days    
Aggregate Intrinsic Value      
Outstanding at the end of the period (in dollars) 13,845    
Weighted-average grant date fair value of options granted (in dollars per share) $ 3.34 $ 5.44 $ 4.63
Number of nonvested stock options (in shares) 2,281,966 762,999  
Intrinsic value of nonvested stock options 14,000 0  
Aggregate intrinsic value of options exercised   701,000 201,000
Unrecognized compensation cost, net of estimated forfeitures related to unvested stock-based award 6,900,000    
Unrecognized compensation cost related to purchase plan 768,000    
Weighted-average recognition period of unamortized compensation cost 1 year 7 months 6 days 1 year 4 months 24 days  
Number of shares vested 1,513,339 2,128,233  
Weighted-average exercise price for shares vested during the period (in dollars per share) $ 6.64 $ 8.12  
Employee Stock Option Plans | Consultants
      
STOCK-BASED COMPENSATION      
Contractual term of the option 10 years    
Weighted-average assumptions relating to options granted      
Stock-based compensation expense recognized $ 36,000 $ 55,000 $ 0
Number of Shares Underlying Options      
Exercised (in shares) 0