Derivatives - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments,Gain (Loss) [Line Items]
Net gain (loss) on foreign currency exchange contracts	$ 1,865	$ (1,598)	$ 534	$ (1,364)
Not Designated as Hedging Instrument | Foreign Currency Exchange Contracts | Other Income (Expense), Net
Derivative Instruments,Gain (Loss) [Line Items]
Net gain (loss) on foreign currency exchange contracts	$ 1,900	$ (1,600)	$ 500	$ (1,400)