Consolidated Statements of Stockholders' Equity - USD ($)
$ in Thousands
Total
Preferred Stock [Member]
Common Stock [Member]
Additional Paid-in Capital [Member]
Treasury Stock [Member]
Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2013 $ 19,821   $ 71 $ 284,323 $ (135) $ (264,438)
Preferred stock shares, beginning balance at Dec. 31, 2013 0 0 0 0 0 0
Common stock beginning balance, shares at Dec. 31, 2013     70,683,480      
Stock-based compensation $ 2,605     $ 2,605    
Issuance of common stock from warrant exercises, Cost 938   $ 1 868 $ 69  
Issuance of common stock from warrant exercises, Shares     928,924      
Issuance of common stock and warrants, net of issuance costs 20,061   $ 5 19,698 358  
Issuance of common stock and warrants, net of issuance costs, Shares     5,250,000      
Issuance of common stock under equity compensation plans (448)   $ 1 (157) $ (292)  
Issuance of common stock under equity compensation plans, Shares     844,412      
Net and comprehensive loss (22,082)         $ (22,082)
Ending balance at Dec. 31, 2014 $ 20,895   $ 78 $ 307,337   $ (286,520)
Preferred stock shares, ending balance at Dec. 31, 2014 0 0 0 0 0 0
Common stock ending balance, shares at Dec. 31, 2014     77,706,816      
Stock-based compensation $ 2,929     $ 2,929    
Issuance of common stock from warrant exercises, Cost 976   $ 1 975    
Issuance of common stock from warrant exercises, Shares     966,184      
Issuance of common stock and warrants, net of issuance costs 11,835   $ 4 11,831    
Issuance of common stock and warrants, net of issuance costs, Shares     4,273,719      
Issuance of common stock under equity compensation plans (489)   $ 1 (490)    
Issuance of common stock under equity compensation plans, Shares     773,435      
Net and comprehensive loss (16,422)         $ (16,422)
Ending balance at Dec. 31, 2015 $ 19,724   $ 84 $ 322,582   $ (302,942)
Preferred stock shares, ending balance at Dec. 31, 2015 0 0 0 0 0 0
Common stock ending balance, shares at Dec. 31, 2015 83,720,154   83,720,154      
Stock-based compensation $ 2,868     $ 2,868    
Issuance of common stock from warrant exercises, Cost 163     163    
Issuance of common stock from warrant exercises, Shares     161,366      
Issuance of common stock and warrants, net of issuance costs 4,230   $ 2 4,228    
Issuance of common stock and warrants, net of issuance costs, Shares     2,191,418      
Issuance of common stock under equity compensation plans $ (467)   $ 1 (468)    
Issuance of common stock under equity compensation plans, Shares 3,559,382   556,364      
Net and comprehensive loss $ (15,337)         $ (15,337)
Ending balance at Dec. 31, 2016 $ 11,181   $ 87 $ 329,373   $ (318,279)
Preferred stock shares, ending balance at Dec. 31, 2016 0 0 0 0 0 0
Common stock ending balance, shares at Dec. 31, 2016 86,629,302   86,629,302