Note I - Preferred Stock and Warrants (Details Textual) - USD ($)
$ / shares in Units, $ in Millions
 1 Months Ended 12 Months Ended
Jun. 02, 2014
May 31, 2015
Apr. 30, 2015
Feb. 28, 2015
Dec. 31, 2015
Dec. 31, 2013
Dec. 31, 2016
Preferred Stock, Shares Authorized   10,000,000 10,000,000   10,000,000   10,000,000
Preferred Stock, Par or Stated Value Per Share   $ 0.0001 $ 0.0001   $ 0.0001   $ 0.0001
Conversion of Preferred Stock to Common Stock Upon Initial Public Offering Shares         5,980,564    
Preferred Stock, Shares Outstanding         0   0
2013 Warrants [Member]              
Class of Warrant or Right Issued           1,079,453  
Deerfield Warrant [Member]              
Class of Warrant or Right Issued 14,423,076            
Convertible Notes Payable [Member]              
Debt Instrument, Face Amount           $ 3.8  
Series D-1 Redeemable Convertible Preferred Stock [Member]              
Conversion of Preferred Stock to Common Stock Upon Initial Public Offering Shares         415,584    
Series D-1 Redeemable Convertible Preferred Stock [Member] | Cowen KP Investment LLC [Member]              
Temporary Equity Shares Issuance       3,200,000      
Sale of Stock, Price Per Share       $ 1.25      
Proceeds from Issuance of Redeemable Convertible Preferred Stock       $ 4.0      
Conversion of Preferred Stock to Common Stock Upon Initial Public Offering Shares       415,584      
Series D Redeemable Convertible Preferred Stock [Member]              
Conversion of Preferred Stock to Common Stock Upon Initial Public Offering Shares         967,786    
Class of Warrant or Right, Number of Securities Called by Warrants or Rights     15,499,324     1,079,453  
IPO [Member]              
Stock Issued During Period, Shares, Conversion of Convertible Securities   5,980,564          
Common Stock [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights     2,066,543     143,466  
Class of Warrant or Right, Exercise Price of Warrants or Rights           $ 5.85  
Common Stock [Member] | Deerfield Warrant [Member]              
Class of Warrant or Right, Number of Securities Called by Warrants or Rights 1,923,077            
Class of Warrant or Right, Exercise Price of Warrants or Rights $ 5.85            
Common Stock [Member] | IPO [Member]              
Stock Issued During Period, Shares, Conversion of Convertible Securities     5,980,564   5,980,564