Marketable Securities (Schedule Of Marketable Securities) (Details) - USD ($) $ in Thousands	Sep. 26, 2020	Dec. 28, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 91,013	$ 52,264
Gross Unrealized Holding Gains	5,346	2,091
Gross Unrealized Holding Losses	(1,218)	(18)
Fair value	102,449	63,538
Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale [Line Items]
Equity securities, Fair Value	7,308	9,201
Municipal Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	91,013	52,264
Gross Unrealized Holding Gains	5,346	2,091
Gross Unrealized Holding Losses	(1,218)	(18)
Fair Value	$ 95,141	$ 54,337

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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