Allowance For Doubtful Accounts - Rollforward (Details) - Allowance for Doubtful Accounts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 7,818	$ 6,498	$ 7,133
Charged to Costs and Expenses	1,375	1,460	(264)
Write-Offs Charged to Allowance	(1,949)	(261)	(296)
Effect of Exchange Rate Changes	(24)	121	(75)
Ending Balance	$ 7,220	$ 7,818	$ 6,498