Hedging Instruments (Derivatives Designated In Cash Flow Hedging Relationships) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Foreign Currency Fair Value Hedge Derivative [Line Items]
Cost of revenue	$ 260,353	$ 239,805	$ 767,062	$ 722,675
Cash flow hedging | Derivatives and non-derivatives designated as hedging instruments | Foreign currency exchange contracts | Costs of revenue
Foreign Currency Fair Value Hedge Derivative [Line Items]
Amount of gain (loss) reclassified from accumulated other comprehensive income into income	$ 3,171	$ 256	$ 7,091	$ (2,412)