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, 2012
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Dec. 31, 2011
Dec. 31, 2010
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 $ 12,617,000 $ 13,168,000 $ 16,436,000
Shares Available For Grant      
Total number of shares of common stock reserved for future issuance 17,470,710    
Employee Stock Purchase Plan
      
Weighted-average assumptions relating to options granted      
Risk-free interest rate (as a percent) 0.20% 0.30% 0.70%
Expected term (in years) 1 year 2 months 12 days 1 year 1 year 4 months 24 days
Dividend yield (as a percent) 0.00% 0.00% 0.00%
Expected volatility (as a percent) 47.40% 61.40% 81.10%
Shares Available For Grant      
Total number of shares of common stock reserved for future issuance 467,747    
Aggregate Intrinsic Value      
Weighted-average recognition period of unamortized compensation cost   1 year 6 months  
Employee Stock Option Plans
      
Weighted-average assumptions relating to options granted      
Risk-free interest rate (as a percent) 0.90% 2.10% 2.30%
Expected term (in years) 5 years 6 months 5 years 2 months 12 days 5 years 3 months 18 days
Dividend yield (as a percent) 0.00% 0.00% 0.00%
Expected volatility (as a percent) 81.50% 84.20% 90.10%
Expiration period 10 years    
Shares Available For Grant      
Outstanding at the beginning of the period (in shares) 4,707,753 2,528,099 2,793,690
Authorized for grant (in shares) 600,000 4,350,000 1,600,000
Total number of shares of common stock reserved for future issuance 16,802,963    
Granted (in shares) (2,149,266) (2,236,270) (1,957,020)
Cancelled (in shares) 40,099 65,924 91,429
Outstanding at the end of the period (in shares) 3,198,586 4,707,753 2,528,099
Number of Shares Underlying Options      
Outstanding at the beginning of the period (in shares) 11,749,359 9,694,001 7,914,869
Granted (in shares) 2,149,266 2,236,270 1,957,020
Exercised (in shares) (254,149) (114,988) (86,459)
Cancelled (in shares) (40,099) (65,924) (91,429)
Outstanding at the end of the period (in shares) 13,604,377 11,749,359 9,694,001
Vested and expected to vest (in shares) 13,569,092    
Exercisable (in shares) 12,841,378 10,982,934 8,934,275
Weighted Average Exercise Price      
Outstanding at the beginning of the period (in dollars per share) $ 12.07 $ 13.22 $ 14.32
Granted (in dollars per share) $ 8.13 $ 6.80 $ 8.60
Exercised (in dollars per share) $ 7.08 $ 6.67 $ 6.60
Cancelled (in dollars per share) $ 19.60 $ 10.95 $ 16.04
Outstanding at the end of the period (in dollars per share) $ 11.52 $ 12.07 $ 13.22
Vested and expected to vest (in dollars per share) $ 11.53    
Exercisable (in dollars per share) $ 11.75 $ 12.38 $ 13.34
Weighted Average Remaining Contractual Term (in years)      
Outstanding at the end of the period 5 years 9 months 4 days    
Exercisable 5 years 7 months 2 days    
Aggregate Intrinsic Value      
Outstanding at the end of the period (in dollars) 16,678    
Exercisable (in dollars) 16,729    
Weighted-average grant date fair value of options granted (in dollars per share) $ 5.44 $ 4.63 $ 6.14
Number of nonvested stock options (in shares) 762,999 766,425  
Intrinsic value of nonvested stock options   699,000  
Aggregate intrinsic value of options exercised 701,000 201,000 122,000
Unrecognized compensation cost, net of estimated forfeitures related to unvested stock-based award 2,600,000    
Unrecognized compensation cost related to purchase plan 742,000    
Weighted-average recognition period of unamortized compensation cost 2 years 2 months 12 days    
Number of shares vested 2,128,233 2,121,922  
Weighted-average exercise price of vested shares (in dollars per share) $ 8.12 $ 8.27  
Employee Stock Option Plans | Consultants
      
Weighted-average assumptions relating to options granted      
Stock-based compensation expense recognized $ 55,000   $ 31,000