Stockholders' Equity - Common Stock and Warrants (Details) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Dec. 31, 2016
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Jan. 31, 2014
Dec. 31, 2013
Feb. 28, 2013
Stockholders' equity              
Common Stock, par value (in dollars per share) $ 0.01 $ 0.01 $ 0.01        
Common Stock, Shares, Outstanding 191,141,646 191,141,646 180,087,491        
Shares of common stock issuances 10,400,000     36,502,440      
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares) 3,120,000 3,120,000          
Shares of common stock sold in an underwritten public offering (in shares)       26,502,440      
Net proceeds from public offering $ 11,900 $ 27,500   $ 165,700      
Proceeds from Issuance of Warrants       $ 11,800      
Common stock shares callable per warrant 1 1          
Exercise price of warrants (in dollars per share) $ 1.50 $ 1.50          
Number of warrants exercised (in shares)   119,879 26,882 23,918,429      
Shares issued result of exercise of warrants (in shares)   119,879 26,882 23,832,038      
Proceeds from exercise of warrants   $ 111 $ 25 $ 18,340      
Increase in Paid-in capital and reduction of warrant liability   $ 141 $ 22 $ 83,400      
Warrants outstanding (in shares) 14,501,600 14,501,600 4,192,567        
Minimum              
Stockholders' equity              
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)       $ 5.50      
Maximum              
Stockholders' equity              
Per share price of shares of common stock sold in an underwritten public offering (in dollars per share)       $ 5.74      
Underwriters agreement              
Stockholders' equity              
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares) 7,381,500 7,381,500          
Warrants issued in February, 2013              
Stockholders' equity              
Exercise price of warrants (in dollars per share)             $ 0.15
Warrants outstanding (in shares) 100 100 100 100      
Warrants issued in February, 2013 | Minimum              
Stockholders' equity              
Exercise price of warrants (in dollars per share)           $ 0.15  
Warrants issued in January, 2014              
Stockholders' equity              
Shares of common stock that can be purchased from warrants issued in an underwritten public offering (in shares)       4,000,000      
Number of shares of common stock in each fixed combination of shares and the warrants sold (in shares)       1      
Number of warrants in each fixed combination of shares and the warrants sold to purchase one share of common stock (in shares)       0.40      
Price of per fixed combination of the shares and the warrants sold (in dollars per share)       $ 3.00      
Number of share sold in a fixed combination of shares and warrants (in shares)       10,000,000      
Exercise price of warrants (in dollars per share) $ 1.025 $ 1.025   $ 4.00 $ 4.00    
Number of warrants exercised (in shares)   0 0 0      
Warrants issued in December 2016              
Stockholders' equity              
Exercise price of warrants (in dollars per share) $ 1.50 $ 1.50          
Number of warrants exercised (in shares)   0