Accumulated Other Comprehensive Loss (Schedule Of Accumulated Other Comprehensive Loss By Component) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated other comprehensive income loss [Line Items]
Accumulated other comprehensive loss, net of tax, beginning balance	$ (14,176)	$ (13,016)	$ (9,475)
Other comprehensive gain (loss) before reclassifications	6,027	(1,159)	(3,528)
Amounts reclassified from accumulated other comprehensive loss	0	(1)	(13)
Net current period other comprehensive gain (loss)	6,027	(1,160)	(3,541)
Accumulated other comprehensive loss, net of tax, ending balance	(8,149)	(14,176)	(13,016)
Foreign currency translaction adjustments [Member]
Accumulated other comprehensive income loss [Line Items]
Accumulated other comprehensive loss, net of tax, beginning balance	(14,544)	(13,079)	(9,688)
Other comprehensive gain (loss) before reclassifications	4,977	(1,465)	(3,391)
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Net current period other comprehensive gain (loss)	4,977	(1,465)	(3,391)
Accumulated other comprehensive loss, net of tax, ending balance	(9,567)	(14,544)	(13,079)
Derivative instruments, net of tax [Member]
Accumulated other comprehensive income loss [Line Items]
Accumulated other comprehensive loss, net of tax, beginning balance	286	0	0
Other comprehensive gain (loss) before reclassifications	1,192	286	0
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Net current period other comprehensive gain (loss)	1,192	286	0
Accumulated other comprehensive loss, net of tax, ending balance	1,478	286	0
Unrealized loss on investments, net of tax [Member]
Accumulated other comprehensive income loss [Line Items]
Accumulated other comprehensive loss, net of tax, beginning balance	(74)	(95)	(64)
Other comprehensive gain (loss) before reclassifications	33	21	(31)
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Net current period other comprehensive gain (loss)	33	21	(31)
Accumulated other comprehensive loss, net of tax, ending balance	(41)	(74)	(95)
Other, net of tax [Member]
Accumulated other comprehensive income loss [Line Items]
Accumulated other comprehensive loss, net of tax, beginning balance	156	158	277
Other comprehensive gain (loss) before reclassifications	(175)	(1)	(106)
Amounts reclassified from accumulated other comprehensive loss	0	(1)	(13)
Net current period other comprehensive gain (loss)	(175)	(2)	(119)
Accumulated other comprehensive loss, net of tax, ending balance	$ (19)	$ 156	$ 158