Derivative Contracts - Effect of Derivative Instruments on Consolidated Statements of Operations for Derivatives not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Income on Derivatives	$ 2,489	$ 1,555
Foreign exchange contract | Cost of Revenues | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Income on Derivatives	1,232	1,555
Interest swap contract | Interest Income | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Recognized in Income on Derivatives	$ 1,162	$ 0