Financial Instruments And Risk Management (Gross Notional Amount Of Outstanding Derivative Instruments) (Details) - Currency Forward Contracts [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Derivative Instruments Designated As Cash Flow Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Currency forward contracts	$ 584,107	$ 448,448	$ 233,500
Derivative Instruments Not Designated As Cash Flow Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Currency forward contracts	$ 234,579	$ 231,161	$ 168,361