Marketable Securities (Schedule Of Maturities of Marketable Securities) (Details) - USD ($) $ in Thousands	Mar. 28, 2020	Dec. 28, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 52,572	$ 52,264
Marketable Securities, Excluding Equity Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost, Due within one year	5,437
Amortized Cost, Due after one year through five years	28,190
Amortized Cost, Due after five years through ten years	18,945
Amortized Cost	52,572
Fair Value, Due within one year	5,457
Fair Value, Due after one year through five years	28,996
Fair Value, Due after five years through ten years	20,318
Fair Value	$ 54,771

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-Section 45
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-Subparagraph (b)
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