v3.8.0.1
Note 9 - Warrants (Details Textual)
$ / shares in Units, $ in Thousands
 1 Months Ended 6 Months Ended 12 Months Ended
Sep. 18, 2015
$ / shares
shares
Dec. 16, 2013
$ / shares
shares
Sep. 30, 2016
USD ($)
$ / shares
shares
Dec. 31, 2013
USD ($)
$ / shares
$ / item
shares
Jun. 30, 2012
USD ($)
$ / shares
shares
Jun. 30, 2016
$ / shares
Dec. 31, 2017
USD ($)
shares
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
shares
Sep. 30, 2015
USD ($)
Sep. 17, 2015
$ / shares
Common Stock Warrants Exercised                 847,058    
Stock Issued During Period, Shares, Common Stock Warrants Exercised                 527,101    
2012 Private Placement [Member]                      
Fair Value of Warrant Upon Execution of Securities Purchase Agreement | $         $ 5,800            
Other Expenses | $             $ 300 $ 600 $ 2,100    
Hercules Warrants [Member]                      
Common Stock Warrants Exercised 176,730 176,730 176,730 176,730              
Investment Warrants, Exercise Price | $ / shares     $ 3.07 $ 6.79   $ 3.88          
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares $ 3.88 $ 6.79 $ 3.07 $ 9.67             $ 6.79
Warrant Exercisable Term       5 years              
Fair Value of Warrant On Date Of Issuance | $     $ 45 $ 1,100           $ 100  
Derivative, Price Risk Option Strike Price | $ / item       6.79              
Class of Warrant or Right Fair Value Assumption Risk Free Interest Rate       1.55%              
Class of Warrant or Right Fair Value Assumption Stock Volatility       71.00%              
Class of Warrant or Right Fair Value Assumption Expected Dividend Yield       0.00%              
Class of Warrant or Right, Outstanding             176,730        
PIPE Warrants [Member]                      
Investment Warrants, Exercise Price | $ / shares         $ 3.40            
Warrant Exercisable Term         5 years            
Class of Warrant or Right, Outstanding         2,630,103   512,456        
Warrants Vesting Condition Description         50.00%