Note I - Preferred Stock and Warrants - Summary of Redeemable Convertible Preferred Stock Activity (Details) - shares
 12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2016
Dec. 31, 2013
Balance (in shares)    
Less: Conversion of preferred stock into common stock upon IPO (in shares) (5,980,564)      
Scenario, Previously Reported [Member]        
Balance (in shares)   41,737,048   34,481,623
Stock Issued During Period, Shares, Conversion of Convertible Securities   5,332,348    
Shares issued for financing fee to Deerfield (in shares)   1,923,077    
Temporary Equity Shares Issuance 3,200,000      
Exercise of Series D preferred warrants (in shares) 3,205      
Restatement Adjustment [Member]        
Effect of reverse stock split (in shares) (38,959,689)      
Series A Redeemable Convertible Preferred Stock [Member]        
Balance (in shares)    
Less: Conversion of preferred stock into common stock upon IPO (in shares) (1,293,838)      
Series A Redeemable Convertible Preferred Stock [Member] | Scenario, Previously Reported [Member]        
Balance (in shares)   9,704,215   9,704,215
Stock Issued During Period, Shares, Conversion of Convertible Securities      
Shares issued for financing fee to Deerfield (in shares)      
Temporary Equity Shares Issuance      
Exercise of Series D preferred warrants (in shares)      
Series A Redeemable Convertible Preferred Stock [Member] | Restatement Adjustment [Member]        
Effect of reverse stock split (in shares) (8,410,377)      
Series B Redeemable Convertible Preferred Stock [Member]        
Balance (in shares)    
Less: Conversion of preferred stock into common stock upon IPO (in shares) (829,234)      
Series B Redeemable Convertible Preferred Stock [Member] | Scenario, Previously Reported [Member]        
Balance (in shares)   6,220,000   6,220,000
Stock Issued During Period, Shares, Conversion of Convertible Securities      
Shares issued for financing fee to Deerfield (in shares)      
Temporary Equity Shares Issuance      
Exercise of Series D preferred warrants (in shares)      
Series B Redeemable Convertible Preferred Stock [Member] | Restatement Adjustment [Member]        
Effect of reverse stock split (in shares) (5,390,766)      
Series C Redeemable Convertible Preferred Stock [Member]        
Balance (in shares)    
Less: Conversion of preferred stock into common stock upon IPO (in shares) (2,474,122)      
Series C Redeemable Convertible Preferred Stock [Member] | Scenario, Previously Reported [Member]        
Balance (in shares)   18,557,408   18,557,408
Stock Issued During Period, Shares, Conversion of Convertible Securities      
Shares issued for financing fee to Deerfield (in shares)      
Temporary Equity Shares Issuance      
Exercise of Series D preferred warrants (in shares)      
Series C Redeemable Convertible Preferred Stock [Member] | Restatement Adjustment [Member]        
Effect of reverse stock split (in shares) (16,083,286)      
Series D Redeemable Convertible Preferred Stock [Member]        
Balance (in shares)    
Less: Conversion of preferred stock into common stock upon IPO (in shares) (967,786)      
Series D Redeemable Convertible Preferred Stock [Member] | Scenario, Previously Reported [Member]        
Balance (in shares)   7,255,425  
Stock Issued During Period, Shares, Conversion of Convertible Securities   5,332,348    
Shares issued for financing fee to Deerfield (in shares)   1,923,077    
Temporary Equity Shares Issuance      
Exercise of Series D preferred warrants (in shares) 3,205      
Series D Redeemable Convertible Preferred Stock [Member] | Restatement Adjustment [Member]        
Effect of reverse stock split (in shares) (6,290,844)      
Series D-1 Redeemable Convertible Preferred Stock [Member]        
Balance (in shares)    
Less: Conversion of preferred stock into common stock upon IPO (in shares) (415,584)      
Series D-1 Redeemable Convertible Preferred Stock [Member] | Scenario, Previously Reported [Member]        
Balance (in shares)    
Stock Issued During Period, Shares, Conversion of Convertible Securities      
Shares issued for financing fee to Deerfield (in shares)      
Temporary Equity Shares Issuance 3,200,000      
Exercise of Series D preferred warrants (in shares)      
Series D-1 Redeemable Convertible Preferred Stock [Member] | Restatement Adjustment [Member]        
Effect of reverse stock split (in shares) (2,784,416)