Segment Information (Schedule Of Depreciation And Amortization By Geographic Area) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 62,041	$ 60,535	$ 83,069
Americas [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	25,484	25,892	43,613
EMEA [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	31,135	29,946	34,596
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	$ 5,422	$ 4,697	$ 4,860