Summary of Significant Accounting Policies (Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of Significant Accounting Policies [Abstract]
Beginning balance	$ 26,481	$ 24,518	$ 1,681
Provision for doubtful accounts	551	2,909	22,516
Write-offs, net of recoveries	(591)	(647)	(614)
Currency translation adjustment	(2,561)	(299)	935
Ending balance	$ 23,880	$ 26,481	$ 24,518