Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments And Risk Management (Effect And Classification Of Derivative Instruments) (Details)

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Financial Instruments And Risk Management (Effect And Classification Of Derivative Instruments) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Derivative Instruments Designated As Cash Flow Hedges [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Gain (loss) recognized in other comprehensive income or loss $ 866 $ (7,535) $ 16,493 $ (14,510)
Cost Of Sales [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Gain (loss) reclassified from accumulated other comprehensive income or loss to income or loss for the effective portion (4,192) 1,549 (7,796) 2,500
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net 1,637 1,203 5,458 2,489
Sales [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Gain (loss) reclassified from accumulated other comprehensive income or loss to income or loss for the effective portion 17 0 41 144
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net 4 0 16 5
Other Non-operating Income (Expense) [Member] | Derivative Instruments Designated As Cash Flow Hedges [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net 0 (178)    
Other Non-operating Income (Expense) [Member] | Derivative Instruments Not Designated As Cash Flow Hedges [Member]        
Derivative Instruments, Gain (Loss) [Line Items]        
Gain (loss) recognized in income or loss $ 372 $ (634) $ 2,606 $ (4,045)