Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income [Abstract]
Beginning balance, Unrealized Gain (Loss) on Investments, Net of Tax	$ 20	$ (225)
Beginning balance, Unrealized Gain (Loss) on Derivative Instruments, Net of Tax	4,916	2,217
Beginning balance, Unrealized Gain On Net Investment Hedge, Net Of Tax	4,036	1,894
Beginning balance, Cumulative Translation Adjustment	(52,025)	(46,151)
Other comprehensive income (loss) before reclassifications, Unrealized Gain (Loss) on Investments, Net of Tax	(42)	245	$ (226)
Other comprehensive income (loss) before reclassifications, Unrealized Gain (Loss) on Derivative Instruments, Net of Tax	(10,332)	4,950	8,839
Other comprehensive income (loss) before reclassifications, Unrealized Gain On Net Investment Hedge, Net Of Tax	(8,347)	2,142	1,894
Other comprehensive income (loss) before reclassifications, Cumulative Translation Adjustment	25,107	(5,874)	(30,718)
Gains reclassified from accumulated other comprehensive income, Unrealized Gain (Loss) on Derivative Instruments, Net of Tax	197	(2,251)	(13,983)
Ending balance, Unrealized Gain (Loss) on Investments, Net of Tax	(22)	20	(225)
Ending balance, Unrealized Gain (Loss) on Derivative Instruments, Net of Tax	(5,219)	4,916	2,217
Ending balance, Unrealized Gain On Net Investment Hedge, Net Of Tax	(4,311)	4,036	1,894
Ending balance, Cumulative Translation Adjustment	(26,918)	(52,025)	(46,151)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(43,053)	(42,265)
Accumulated Other Comprehensive Income, before Tax	6,386	1,463
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	197	(2,251)
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (36,470)	$ (43,053)	$ (42,265)