Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Derivatives and Hedging Activities (Schedule of Balance Sheet Classification and Fair Values of Derivative Instruments) (Details)

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Derivatives and Hedging Activities (Schedule of Balance Sheet Classification and Fair Values of Derivative Instruments) (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Derivatives, Fair Value [Line Items]    
Fair value $ (568) $ 1,368
Notional amount 100,873 69,137
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Notional amount 87,700  
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedge [Member]    
Derivatives, Fair Value [Line Items]    
Notional amount 13,200 15,900
Other current assets [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Fair value derivative asset 90 1,440
Notional amount of derivative asset 22,036 39,982
Other current assets [Member] | Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedge [Member]    
Derivatives, Fair Value [Line Items]    
Fair value derivative asset 263 37
Notional amount of derivative asset 13,169 8,348
Accrued expenses and other current liabilities [Member] | Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Fair value derivative liability (921) (48)
Notional amount of derivative liability 65,668 13,273
Accrued expenses and other current liabilities [Member] | Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedge [Member]    
Derivatives, Fair Value [Line Items]    
Fair value derivative liability (61)
Notional amount of derivative liability $ 7,534