Note 13 - Condensed Quarterly Financial Data (Unaudited) (Tables)
12 Months Ended
Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]  
Schedule of Quarterly Financial Information [Table Text Block]
   

Three Months Ended,

 
   

March 31

   

June 30

   

September 30

   

December 31

 
   

(In thousands, except per share data)

 

2014

                               

Operating expenses(1)

  $ 7,160     $ 7,797     $ 8,020     $ 27,858  

Net loss(1)(2)

    (9,616 )     (6,032 )     (6,736 )     (27,578 )

Net loss per share — basic and diluted

    (0.14 )     (0.09 )     (0.09 )     (0.30 )

2013

                               

Operating expenses(3)

  $ 7,991     $ 18,047     $ 7,602     $ 7,583  

Net loss(3)(4)

    (8,288 )     (16,398 )     (7,710 )     (6,363 )

Net loss per share — basic and diluted

    (0.14 )     (0.28 )     (0.12 )     (0.09 )