Note 3 - Receivables (Tables)
 12 Months Ended
Dec. 31, 2016
Notes Tables  
Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]
    December 31,
    2016   2015
Accounts receivable–trade   $
21,816
     $
17,980
  
Less allowance for doubtful receivables    
(567
 )    
(499
 )
Receivables, net   $
21,249
     $
17,481