Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments And Risk Management (Balance Sheet Classification And Fair Value Of Derivative Instruments) (Details)

v3.8.0.1
Financial Instruments And Risk Management (Balance Sheet Classification And Fair Value Of Derivative Instruments) (Details) - Currency Forward Contracts [Member] - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Mar. 31, 2017
Prepaid Expenses And Other Current Assets [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]      
Derivatives, Fair Value [Line Items]      
Fair value of derivative assets $ 998 $ 1,648 $ 6,347
Prepaid Expenses And Other Current Assets [Member] | Derivative Instruments Not Designated As Cash Flow Hedges [Member]      
Derivatives, Fair Value [Line Items]      
Fair value of derivative assets 1,121 683 292
Other Non-Current Assets [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]      
Derivatives, Fair Value [Line Items]      
Fair value of derivative assets 2,492 335 1,619
Accrued Liabilities [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]      
Derivatives, Fair Value [Line Items]      
Fair value of derivative liabilities 11,017 9,336 134
Accrued Liabilities [Member] | Derivative Instruments Not Designated As Cash Flow Hedges [Member]      
Derivatives, Fair Value [Line Items]      
Fair value of derivative liabilities 355 1,229 220
Other Long Term Liabilities [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]      
Derivatives, Fair Value [Line Items]      
Fair value of derivative liabilities $ 7,294 $ 3,820 $ 0