Hedging Instruments (Derivatives Designated In Cash Flow Hedging Relationships) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Foreign Currency Fair Value Hedge Derivative [Line Items]
Cost of revenue	$ 248,313	$ 216,225	$ 482,870	$ 420,055
Cash flow hedging | Derivatives designated as hedging instruments | Foreign currency exchange contracts | Costs of revenue
Foreign Currency Fair Value Hedge Derivative [Line Items]
Amount of (loss) gain reclassified from accumulated other comprehensive income into income	$ (833)	$ 753	$ (2,668)	$ 1,828