Accounts Receivable (Accounts Receivable) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Receivables [Abstract]
Trade receivables	$ 358,388	$ 305,363
Allowance for doubtful accounts	(11,214)	(4,904)
Other allowances	(2,529)	(2,019)
Accounts receivable, net	$ 344,645	$ 298,440