Note 2 - Significant Accounting Policies (Tables)
12 Months Ended
Dec. 31, 2014
Accounting Policies [Abstract]  
Unrealized Gain (Loss) on Investments [Table Text Block]
   

Amortized
Cost

   

Gross
Unrealized
Gains

   

Gross
Unrealized
Losses

   

Fair Value

 
   

(In thousands)

 

As of December 31, 2014:

                               

Cash

  $ 6,351     $     $     $ 6,351  

Money market funds

    4,103                   4,103  

Debt securities of U.S. government agencies

    43,862       1       (19 )     43,844  

Corporate bonds

    9,423       2       (9 )     9,416  

Total

  $ 63,739     $ 3     $ (28 )   $ 63,714  

As of December 31, 2013:

                               

Cash

  $ 3,221     $     $     $ 3,221  

Money market funds

    6,058                   6,058  

Debt securities of U.S. government agencies

    49,878       18       (6 )     49,890  

Corporate bonds

    13,390       4       (1 )     13,393  

Total

  $ 72,547     $ 22     $ (7 )   $ 72,562  
Investments Classified by Contractual Maturity Date [Table Text Block]
   

As of December 31, 2014

   

As of December 31, 2013

 
   

Amortized Cost

   

Fair Value

   

Amortized Cost

   

Fair Value

 
   

(In thousands)

 

Less than one year

  $ 51,338     $ 51,319     $ 56,789     $ 56,806  

Greater than one year but less than five years

    6,050       6,044       12,537       12,535  

Total

  $ 57,388     $ 57,363     $ 69,326     $ 69,341  
Schedule of Property Plant and Equipment Estimated Useful Lives [Table Text Block]
   

Scientific and office equipment (years)

Computer software and equipment (years)

Leasehold improvements and leased equipment

Shorter of useful life or the term of the lease

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]
   

Net unrealized
gains/(losses) on
Available-for-sale
Securities

   

Foreign
Currency
Translation
Adjustment

   

Accumulated
Other
Comprehensive

Loss

 
   

(In thousands)

 

Balance at December 31, 2011

  $ 22     $ (5,066 )   $ (5,044 )

Other comprehensive income

    8             8  

Balance at December 31, 2012

    30       (5,066 )     (5,036 )

Other comprehensive loss

    (15 )           (15 )

Balance at December 31, 2013

    15       (5,066 )     (5,051 )

Other comprehensive loss

    (40 )           (40 )

Balance at December 31, 2014

  $ (25 )   $ (5,066 )   $ (5,091 )