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