Revenue (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Revenue from Contracts with Customer [Line Items]
Accounts receivable, net	$ 323,375	$ 337,927
Contract assets	7,900	7,400
Contract liabilities	1,600	$ 1,700
Revenue recognized from contract liability during the period	$ 1,700
Average transit time	3 days