Accumulated Other Comprehensive Income (Schedule Of Reclassifications out of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jun. 25, 2016	Jul. 01, 2017	Jun. 25, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income	$ 412	$ 682	$ 1,236	$ 1,319
Provision for income taxes	(9,655)	(9,474)	(18,893)	(21,252)
Net income	$ 18,475	$ 15,265	$ 30,311	35,393
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment income				269
Provision for income taxes				(111)
Net income				$ 158