Note Q - Quarterly Results of Operations (unaudited) (Tables)
 12 Months Ended
Dec. 31, 2016
Notes Tables  
Quarterly Financial Information [Table Text Block]
   
Three-Months Ended
  
   
Dec 31,
    
Sep 30,
    
Jun 30,
    
Mar 31,
    
Dec 31,
    
Sep 30,
    
Jun 30,
    
Mar 31,
  
   
2016
    
2016
    
2016
    
2016
    
2015
    
2015
    
2015
    
2015
  
Revenue
   $
—
     $
—
     $
—
     $
—
     $
—
     $
—
     $
—
     $
—
  
Operating expenses:
                                                                
Research and development
    
7,963
      
4,287
      
4,988
      
3,234
      
4,716
      
4,328
      
2,768
      
2,119
  
General and administrative
    
2,873
      
3,104
      
4,287
      
3,736
      
2,566
      
2,152
      
3,188
      
977
  
Restructuring charges
    
—
      
3,010
      
—
      
—
      
—
      
—
      
—
      
—
  
Total operating expenses
    
10,836
      
10,401
      
9,275
      
6,970
      
7,282
      
6,480
      
5,956
      
3,096
  
Loss from operations
    
(10,836
)
    
(10,401
)
    
(9,275
)
    
(6,970
)
    
(7,282
)
    
(6,480
)
    
(5,956
)
    
(3,096
)
Other (expense) income:
                                                                
Loss on extinguishment of debt
    
—
      
—
      
—
      
(4,740
)
    
—
      
—
      
—
      
—
  
Interest expense related to amortization of debt issuance costs and discount
    
(391
)
    
(390
)
    
(393
)
    
(442
)
    
(475
)
    
(479
)
    
(477
)
    
(477
)
Interest expense on principal
    
(1,445
)
    
(1,441
)
    
(1,475
)
    
(1,150
)
    
(698
)
    
(687
)
    
(654
)
    
(632
)
Fair value adjustment
    
2,723
      
(1,299
)
    
20,763
      
10,278
      
(764
)
    
(2,089
)
    
(22,661
)
    
(1,762
)
Interest and other income
    
9
      
98
      
144
      
102
      
15
      
11
      
5
      
—
  
Total other income (expense)
    
896
      
(3,032
)
    
19,039
      
4,048
      
(1,922
)
    
(3,244
)
    
(23,787
)
    
(2,871
)
(Loss) income before income taxes
    
(9,940
)
    
(13,433
)
    
9,764
      
(2,922
)
    
(9,204
)
    
(9,724
)
    
(29,743
)
    
(5,967
)
Income tax benefit (expense)
    
4
      
19
      
4
      
(12
)
    
1
      
(20
)
    
—
      
(7
)
Net (loss) income
   $
(9,936
)
   $
(13,414
)
   $
9,768
     $
(2,934
)
   $
(9,203
)
   $
(9,744
)
   $
(29,743
)
   $
(5,974
)
                                                                 
Net (loss) income per share:
                                                                
Basic
   $
(0.68
)
   $
(0.92
)
   $
0.59
     $
(0.20
)
   $
(0.64
)
   $
(0.68
)
   $
(2.45
)
   $
(2.50
)
Diluted
   $
(0.68
)
   $
(0.92
)
   $
(0.58
)
   $
(0.20
)
   $
(0.64
)
   $
(0.68
)
   $
(2.45
)
   $
(2.50
)