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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Loss) Gain Recognized in Income on Derivatives			$ 2,161	$ 1,236
Foreign exchange contract | Cost of Revenues | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Loss) Gain Recognized in Income on Derivatives	$ (798)	$ 204	434	1,759
Interest swap contract | Interest Income | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (Loss) Gain Recognized in Income on Derivatives	$ 438	$ 523	$ 1,600	$ 523