Prior Year Reclassification (Summary Of Effect Of Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating, general and administrative expenses	$ 231,527	$ 215,282	$ 695,130	$ 637,385
Income from operations	42,806	17,543	136,236	61,662
Other income (expense)	$ (1,218)	(39)	(1,160)	(2,309)
Unrealized (gain) in SERP			(760)	(1,289)
Net cash provided by operating activities			194,181	138,747
Change in SERP investment			(666)	(1,910)
Net cash used in investing activities			$ (118,628)	(74,958)
As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating, general and administrative expenses		215,321		639,694
Income from operations		17,504		59,353
Net cash provided by operating activities				140,036
Change in SERP investment				(3,199)
Net cash used in investing activities				(76,247)
Reclassifications [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Operating, general and administrative expenses		(39)		(2,309)
Income from operations		39		2,309
Other income (expense)		$ (39)		(2,309)
Unrealized (gain) in SERP				(1,289)
Net cash provided by operating activities				(1,289)
Change in SERP investment				1,289
Net cash used in investing activities				$ 1,289