Derivative Financial Instruments (Schedule Of Company's Derivative Instruments On Other Comprehensive Income And The Consolidated Statement Of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivative instruments		$ (3,068)	$ 2,187
Gains (losses) reclassified from OCI into income - effective portion	$ 584	(4,717)	570
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) on derivative instruments	1,416
Unrealized gains (losses) on derivative instruments		(8)	3
Net revenue | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income - effective portion	665	(5,786)	850
Cost of revenue | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income - effective portion	(9)	18	(6)
Research and development | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income - effective portion	83	130	(55)
Sales and marketing | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income - effective portion	(102)	788	(189)
General and administrative | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from OCI into income - effective portion	$ (53)	$ 133	$ (30)