Valuation And Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reserves For Doubtful Accounts Receivable [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 4,523	$ 5,128	$ 4,306
Charges to Costs and Expenses	591	822	2,200
Write-Offs/Cash Payments	(1,660)	(531)	(817)
Foreign Currency Translation	1,122	(896)	(561)
Balance at End of Year	4,576	4,523	5,128
Valuation Allowance For Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	4,891	4,446	4,678
Charges to Costs and Expenses	1,789	885	634
Write-Offs/Cash Payments	(679)	(816)	(468)
Foreign Currency Translation	210	376	(398)
Balance at End of Year	$ 6,211	$ 4,891	$ 4,446