Note E - Revenue and Contract Liabilities - Schedule Of Contract Liabilities From Contract With Customers (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019
Contract liabilities at beginning of period	$ 13,852	$ 15,055
Increase due to deferral of revenue at period end	19,363	13,852
Decrease due to beginning contract liabilities recognized as revenue	(13,612)	(15,055)
Contract liabilities at end of period	$ 19,603	$ 13,852