Annual report pursuant to Section 13 and 15(d)

Accounts Receivable, Net (Components of Accounts Receivable) (Details)

v3.8.0.1
Accounts Receivable, Net (Components of Accounts Receivable) (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Receivables [Abstract]    
Trade accounts receivable $ 373,905 $ 342,234
Allowance for doubtful accounts (9,043) (8,556)
Accounts receivable, net $ 364,862 $ 333,678