Note 13 - Stock-based Compensation Plan (Tables)
12 Months Ended
Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]
   

For the Years Ended December 31,

 
   

2014

   

2013

   

2012

 

Research and development

  $ 650     $ 311     $ 148  

General and administrative

    1,441       863       528  

Total

  $ 2,091     $ 1,174     $ 676  
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]
   

For the Years Ended December 31,

 
   

2014

   

2013

   

2012

 

Expected Life of the Option Term (years)

    3.7       3.9       3.9  

Risk-free interest rate

    1.2 %     0.9 %     1.2 %

Dividend rate

    0 %     0 %     0 %

Volatility

    76.2 %     83.8 %     73.9 %

Forfeiture rate

    5.3 %     8.1 %     9.0 %
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]
   

Options
outstanding

   

Weighted
average
exercise
price

 

Underlying Exercise Price Currency

 

Weighted average
remaining
contractual term
(in years)

   

Aggregate
intrinsic
value

 

Outstanding at January 1, 2012

    191     $ 30.16  

CND

    3.2     $  

Options granted

    102       16.12  

CND

               

Options expired

    (29 )     37.44  

CND

               

Options forfeited

    (23 )     25.48  

CND

               

Outstanding at December 31, 2012

    241     $ 23.92  

CND

    3.5     $  

Options granted

    71       13.00  

CND

               

Options granted

    1,114       4.41  

US

               

Options expired

    (14 )     41.02  

CND

               

Options forfeited

    (50 )     27.83  

CND

               

Outstanding at December 31, 2013

    1,362     $ 7.10  

US

    4.5     $  

Options granted

    87       2.57  

US

               

Options expired

    (5 )     27.16  

CND

               

Options forfeited

    (12 )     29.89  

CND

               

Options forfeited

    (54 )     4.41  

US

               

Outstanding at December 31, 2014

    1,378     $ 6.65  

US

    3.6     $  

Vested or expected to vest at December 31, 2014

    1,326     $ 6.26  

US

    3.6     $  

Exercisable at December 31, 2014

    635     $ 7.48  

US

    3.5     $