Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments And Risk Management (Gross Notional Amount Of Outstanding Derivative Instruments) (Details)

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Financial Instruments And Risk Management (Gross Notional Amount Of Outstanding Derivative Instruments) (Details) - Currency Forward Contracts [Member] - USD ($)
$ in Thousands
Sep. 30, 2018
Dec. 31, 2017
Sep. 30, 2017
Derivative Instruments Designated As Cash Flow Hedges [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Currency forward contracts $ 434,738 $ 448,448 $ 390,500
Derivative Instruments Not Designated As Cash Flow Hedges [Member]      
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]      
Currency forward contracts $ 289,772 $ 231,161 $ 181,045