XML 38 R20.htm IDEA: XBRL DOCUMENT v3.8.0.1
Note 2 - Investments (Tables)
 3 Months Ended
Mar. 31, 2018
Notes Tables  
Available-for-sale Securities [Table Text Block]
   
March 31, 2018
    
December 31, 2017
  
   
Amortized
cost
    
Unrealized
loss
    
Fair market
value
    
Amortized
cost
    
Unrealized
loss
    
Fair market
value
  
Corporate bonds
   $
34,394
     $
(36
)
   $
34,358
     $
33,778
     $
(20
)
   $
33,758