Schedule II - Valuation and Qualifying Accounts (Tables)
 12 Months Ended
Dec. 31, 2016
Notes Tables  
Summary of Allowance for Doubtful Accounts and Revenue Adjustments [Table Text Block]
    2016   2015   2014
Balance at beginning of year   $
499
     $
502
     $
512
  
Provision for bad debt    
126
      
16
      
63
  
Write-offs, net of recoveries    
(58
 )    
(19
 )    
(73
 )
Balance at end of year   $
567
     $
499
     $
502