Derivative Financial Instruments (Schedule Of Company's Derivative Instruments On Other Comprehensive Income And The Consolidated Statement Of Operations) (Details) - Derivatives Designated As Hedging Instruments [Member] - Foreign Currency Forward Contracts [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in OCI-Effective Portion	$ (10,692)	$ 3,007	$ 453
Gain or (Loss) Reclassified from OCI into Income-Effective Portion	(7,624)	820	453
Amount of Gain or (Loss) Recognized in Income and Excluded from Effectiveness Testing	1,587	365	(52)
Net Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Reclassified from OCI into Income-Effective Portion	(8,693)	1,100	462
Cost Of Revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Reclassified from OCI into Income-Effective Portion	18	(6)	6
Operating Expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Reclassified from OCI into Income-Effective Portion	1,051	(274)	(15)
Other Income (Expense), net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income and Excluded from Effectiveness Testing	$ 1,587	$ 365	$ (52)