| Compensation and Other Benefit Plans (Tables)
 | 12 Months Ended | 
      
        | Dec. 31, 2013 | 
      
        | Compensation and Other Benefit Plans [Abstract] |  | 
      
        | Stock option activity | 
A summary of the status of the Company’s stock option plans as of December 31, 2013, 2012, and 2011, and changes during the years ended on those dates is presented below: 
 
|  |  | 2013 |  |  | 2012 |  |  | 2011 |  |  
| Options: |  | Shares |  |  | Price* |  |  | Shares |  |  | Price* |  |  | Shares |  |  | Price* |  |  
| Outstanding at beginning of year |  |  | 6,788,383 |  |  | $ | 8.99 |  |  |  | 5,053,435 |  |  | $ | 12.55 |  |  |  | 2,331,450 |  |  | $ | 25.36 |  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Granted |  |  | 1,168,203 |  |  | $ | 3.13 |  |  |  | 2,351,445 |  |  | $ | 2.59 |  |  |  | 2,920,166 |  |  | $ | 2.81 |  |  
| Exercised |  |  | (589,355 | ) |  | $ | 2.26 |  |  |  | (90,252 | ) |  | $ | 1.68 |  |  |  | - |  |  | $ | - |  |  
| Forfeited, expired or cancelled |  |  | (151,190 | ) |  | $ | 17.46 |  |  |  | (526,245 | ) |  | $ | 15.84 |  |  |  | (198,181 | ) |  | $ | 35.56 |  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Outstanding at end of year |  |  | 7,216,041 |  |  | $ | 8.42 |  |  |  | 6,788,383 |  |  | $ | 8.99 |  |  |  | 5,053,435 |  |  | $ | 12.55 |  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
| Exercisable at end of year |  |  | 4,814,926 |  |  | $ | 11.14 |  |  |  | 4,276,834 |  |  | $ | 12.42 |  |  |  | 3,366,807 |  |  | $ | 16.33 |  | 
 
| * | Weighted-average exercise price | 
 | 
      
        | Unvested RSU activity | 
Unvested RSU activity for the year ended December 31, 2013 is summarized below:   
|  |  | Number of Shares |  |  | Weighted- Average Grant- Date Fair Value |  |  
| Unvested balance at December 31, 2012 |  |  | 1,459,853 |  |  | $ | 2.75 |  |  
| Granted |  |  | 958,385 |  |  | $ | 2.96 |  |  
| Vested |  |  | (637,034 | ) |  | $ | 2.57 |  |  
| Forfeited |  |  | (43,167 | ) |  | $ | 2.08 |  |  
| Unvested balance at December 31, 2013 |  |  | 1,738,037 |  |  | $ | 2.73 |  |   | 
      
        | Weighted average assumptions | 
The fair value of stock option awards was estimated using the Black-Scholes model with the following weighted average assumptions for the years ended December 31, 2013, 2012, and 2011: 
 
|  |  | Year Ended December 31, |  |  
|  |  | 2013 |  |  | 2012 |  |  | 2011 |  |  
| Dividend yield |  |  | 0 | % |  |  | 0 | % |  |  | 0 | % |  
| Expected volatility |  |  | 92 | % |  |  | 92 | % |  |  | 88 | % |  
| Risk-free interest rate |  |  | 0.89 | % |  |  | 0.82 | % |  |  | 1.48 | % |  
| Expected term |  | 5.6 years |  |  | 5.6 years |  |  | 5.4 years |  | 
 | 
      
        | Stock-based compensation expense | 
The following table shows total stock-based compensation expense included in the consolidated statements of comprehensive loss for the years ended December 31, 2013, 2012, and 2011 (in thousands): 
 
|  |  | Year Ended December 31, |  |  
|  |  | 2013 |  |  | 2012 |  |  | 2011 |  |  
| Research and development |  | $ | 2,358 |  |  | $ | 2,391 |  |  | $ | 3,672 |  |  
| Selling, general and administrative |  |  | 2,741 |  |  |  | 1,893 |  |  |  | 4,087 |  |  
| Total stock-based compensation expense |  | $ | 5,099 |  |  | $ | 4,284 |  |  | $ | 7,759 |  | 
 |