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Schedule II - Valuation and Qualifying Accounts (Tables)
12 Months Ended
Dec. 31, 2020
Notes Tables  
Summary of Valuation Allowance [Table Text Block]
              

Balance

 
  

Balance at

          

at

 
  

Beginning

  

Additions

      

End of

 

Description

 

of period

  

at Cost

  

Deductions

  

Period

 

Year Ended December 31, 2018

                

Deducted in balance sheet from trade accounts receivables:

                

Allowance for doubtful accounts

 $1,800   900      2,700 

Year Ended December 31, 2019

                

Deducted in balance sheet from trade accounts receivables:

                

Allowance for doubtful accounts

 $2,700      2,630   70 

Year Ended December 31, 2020

                

Deducted in balance sheet from trade accounts receivables:

                

Allowance for credit losses

 $70   1,446      1,516