Quarterly report pursuant to Section 13 or 15(d)

Revenue And Contract Liabilities (Schedule Of Contract Liabilities From Contract With Customers) (Details)

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Revenue And Contract Liabilities (Schedule Of Contract Liabilities From Contract With Customers) (Details) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 27, 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 15,972 13,852
Decrease due to beginning contract liabilities recognized as revenue (13,372) (15,055)
Contract liabilities at end of period $ 16,452 $ 13,852