Annual report pursuant to Section 13 and 15(d)

Financial Instruments and Risk Management (Effect and Classification of Derivative Instuments) (Details)

v3.8.0.1
Financial Instruments and Risk Management (Effect and Classification of Derivative Instuments) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain (Loss) recognized in other comprehensive income, net of tax $ (15,862) $ 583 $ 9,791
Designated as Hedging Instrument [Member] | Cost of Sales [Member] | Cash Flow Hedging [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain (Loss) reclassified from accumulated other comprehensive income to income for the effective portion 1,195 (724) 15,446
Loss reclassified from accumulated other comprehensive income to income as a result of cash flow hedge discontinuance 0 (24) 0
Loss recognized in income for amount excluded from effectiveness testing and for the ineffective portion 2,843 1,240 (209)
Designated as Hedging Instrument [Member] | Sales [Member] | Cash Flow Hedging [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain (Loss) reclassified from accumulated other comprehensive income to income for the effective portion 144 115 385
Loss recognized in income for amount excluded from effectiveness testing and for the ineffective portion 6 1 (30)
Designated as Hedging Instrument [Member] | Other Non-Operating Income (Expense) [Member] | Cash Flow Hedging [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Loss reclassified from accumulated other comprehensive income to income as a result of cash flow hedge discontinuance (178) 0 0
Not Designated as Hedging Instrument [Member] | Other Non-Operating Income (Expense) [Member]      
Derivative Instruments, Gain (Loss) [Line Items]      
Gain (Loss) recognized in income $ (3,943) $ 2,739 $ 2,838