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

Derivatives and Hedging Activities (Narrative) (Details)

v3.8.0.1
Derivatives and Hedging Activities (Narrative) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Derivatives, Fair Value [Line Items]    
Gain (loss) on derivative instrument $ 5,000 $ 2,100
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] | Cash Flow Hedge [Member] | Designated as Hedging Instrument [Member]    
Derivatives, Fair Value [Line Items]    
Notional amount $ 13,200 $ 15,900