Financial Instruments And Risk Management (Gross Notional Amount Of Outstanding Derivative Instruments) (Details) - Currency Forward Contracts [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Derivative Instruments Designated As Cash Flow Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Currency forward contracts	$ 390,500	$ 206,000	$ 204,000
Derivative Instruments Not Designated As Cash Flow Hedges [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Currency forward contracts	$ 181,045	$ 184,940	$ 189,159