Derivatives Balance Sheet Location (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Other Current Assets
Derivatives, Fair Value [Line Items]
Derivative assets	$ 1,323	$ 730
Other Current Assets | Foreign currency forward contracts | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,079	678
Other Current Assets | Foreign currency forward contracts | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	244	52
Accrued Expenses
Derivatives, Fair Value [Line Items]
Derivative liabilities	2,652	2,120
Accrued Expenses | Foreign currency forward contracts | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	2,638	1,990
Accrued Expenses | Foreign currency forward contracts | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 14	$ 130