Marketable Securities (Schedule Of Marketable Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 52,359	$ 55,476
Gross Unrealized Holding Gains	6,670	8,305
Gross Unrealized Holding Losses	(295)	(116)
Fair Value	58,734	63,665
Equity Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,198	1,198
Gross Unrealized Holding Gains	6,396	7,634
Gross Unrealized Holding Losses	0	0
Fair Value	7,594	8,832
Municipal Bonds [Member] \| Fair Value, Inputs, Level 2 [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	51,161	54,278
Gross Unrealized Holding Gains	274	671
Gross Unrealized Holding Losses	(295)	(116)
Fair Value	$ 51,140	$ 54,833

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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