| Revenue And Contract Liabilities (Schedule Of Contract Liabilities From Contract With Customers) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended | 
|---|---|---|
| Mar. 28, 2020 | Dec. 28, 2019 | |
| Revenue And Contract Liabilities [Abstract] | ||
| Contract liabilities at beginning of period | $ 13,852 | $ 15,055 | 
| Increase due to deferral of revenue at period end | 13,361 | 13,852 | 
| Decrease due to beginning contract liabilities recognized as revenue | (13,132) | (15,055) | 
| Contract liabilities at end of period | $ 14,081 | $ 13,852 | 
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- Definition Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- References No definition available. 
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- Definition Contract with Customer, Liability, Increase (Decrease) In Deferred Revenue No definition available. 
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- Definition Contract with Customer, Liability, Increase (Decrease) Revenue Recognized No definition available. 
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