Significant Accounting Policies Trade Accounts Receivable and Allowance for Doubtful Accounts (Policies)

12 Months Ended

Dec. 31, 2017

Trade accounts receivable and allowance for doubtful accounts [Abstract]

Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block]

Trade accounts receivable and allowance for doubtful accounts

Our trade accounts receivable balance is stated at the amount owed by our customers, net of allowances for estimated uncollectible balances. We maintain allowances for doubtful accounts for estimated losses expected to result from the inability of our customers to make required payments. These estimates are based on management’s evaluation of the ability of customers to make payments, with emphasis on historical remittance experience, known customer financial difficulties and the age of receivable balances. Accounts receivable are charged to the allowance when it is determined they are no longer collectible. Our allowance for doubtful accounts was $11.0 million and $9.4 million at December 31, 2017 and 2016, respectively. Amounts charged to selling, general and administrative expenses or deducted from the allowance were not significant to our statement of operations in the years ended December 31, 2017, 2016 and 2015.