Retirement Plans (Schedule Of Costs Of Retirement Plan) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Defined Benefit Plan Disclosure [Line Items]
Pension Cost (Reversal of Cost)	$ 6,218	$ 4,733	$ 4,423
Retirement savings plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Cost (Reversal of Cost)	4,949	3,434	3,525
Deferred compensation plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Cost (Reversal of Cost)	806	801	508
Supplemental executive retirement plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Cost (Reversal of Cost)	$ 463	$ 498	$ 390