Note 1 - Summary of Significant Accounting Policies - Reported Share-based Compensation in Consolidated Financial Statements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 26, 2021	Jun. 27, 2020	Jun. 26, 2021	Jun. 27, 2020
Share-based compensation of continuing operations	$ 3,506	$ 3,403	$ 7,029	$ 7,014
Income tax benefit	(180)	(223)	(414)	(395)
Total share-based compensation, net	3,326	3,180	6,615	6,619
Cost of Sales [Member]
Share-based compensation of continuing operations	191	211	453	423
Research and Development Expense [Member]
Share-based compensation of continuing operations	763	828	1,544	1,661
Selling, General and Administrative Expenses [Member]
Share-based compensation of continuing operations	$ 2,552	$ 2,364	$ 5,032	$ 4,930