Quarterly report pursuant to Section 13 or 15(d)

Stock-based Compensation (Details)

v2.4.0.8
Stock-based Compensation (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2014
Mar. 31, 2013
Dec. 31, 2012
Stock-based awards weighted average assumptions [Abstract]      
Dividend yield (in hundredths) 0.00% 0.00%  
Expected volatility (in hundredths) 94.00% 92.00%  
Risk free interest rate (in hundredths) 1.73% 0.78%  
Expected term 5 years 7 months 6 days 5 years 7 months 6 days  
Stock option activity [Roll Forward]      
Options outstanding beginning of period (in shares) 7,218,241    
Granted (in shares) 1,099,239    
Exercised (in shares) (640,649)    
Forfeited, expired or cancelled (in shares) (116,766)    
Options outstanding end of period (in shares) 7,560,065    
Options exercisable at end period (in shares) 4,562,868    
Stock options activity, weighted average exercise price [Roll Forward]      
Options outstanding, beginning of period (in dollars per share) $ 8.42    
Granted (in dollars per share) $ 8.56    
Exercised (in dollars per share) $ 4.72    
Forfeited, expired or cancelled (in dollars per share) $ 24.72    
Options outstanding, end of period (in dollars per share) $ 8.50    
Options exercisable weighted average exercise price (in dollars per share) $ 10.85    
Additional Disclosures [Abstract]      
Options outstanding weighted average remaining contractual term beginning of period 7 years 1 month 20 days   6 years 9 months
Options outstanding weighted average remaining contractual term end of period 7 years 1 month 20 days   6 years 9 months
Options exercisable weighted average remaining contractual term 5 years 11 months 12 days    
Options outstanding, aggregate intrinsic value at beginning of period $ 18,213    
Options outstanding, aggregate intrinsic value at end of period 9,892    
Options exercisable, aggregate intrinsic value 5,422    
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense 3,924 1,619  
Research and Development [Member]
      
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense 2,406 997  
Selling, General and Administrative Expenses [Member]
      
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Total stock-based compensation expense $ 1,518 $ 622  
Stock Options [Member] | Director [Member]
      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 4 years    
Restricted Stock Units (RSUs) [Member]
      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Vesting period 3 years    
Unvested RSU activity [Roll Forward]      
Unvested balance beginning of period (in shares) 1,738,037    
Granted (in shares) 972,614    
Vested (in shares) (478,845)    
Forfeited (in shares) (77,536)    
Unvested balance end of period (in shares) 2,154,270    
Unvested RSU activity, weighted average grant date fair value [Roll Forward]      
Unvested balance, beginning of period (in dollars per share) $ 2.73    
Granted (in dollars per share) $ 8.64    
Vested (in dollars per share) $ 4.16    
Forfeited (in dollars per share) $ 2.82    
Unvested balance, end of period (in dollars per share) $ 5.08    
Long Term Incentive Plan [Member] | Stock Options [Member]
      
Stock option activity [Roll Forward]      
Granted (in shares) 1,099,239    
Long Term Incentive Plan [Member] | Restricted Stock Units (RSUs) [Member]
      
Stock option activity [Roll Forward]      
Granted (in shares) 972,614