Accumulated Other Comprehensive Income (Schedule Of Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and interest expense	$ 2,895	$ (532)
Provision for income taxes	(4,570)	(6,116)
Net income	14,304	16,191
Unrealized Gain On Available-For-Sale Marketable Securities [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income and interest expense		54
Provision for income taxes		(15)
Net income		$ 39