Note 1 - Summary of Significant Accounting Policies - Reported Share-based Compensation in Consolidated Financial Statements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2021	Sep. 26, 2020	Sep. 25, 2021	Sep. 26, 2020
Share-based compensation of continuing operations	$ 3,714	$ 3,299	$ 10,743	$ 10,313
Income tax benefit	(155)	(215)	(569)	(610)
Total share-based compensation, net	3,559	3,084	10,174	9,703
Cost of Sales [Member]
Share-based compensation of continuing operations	239	218	692	641
Research and Development Expense [Member]
Share-based compensation of continuing operations	889	782	2,433	2,443
Selling, General and Administrative Expenses [Member]
Share-based compensation of continuing operations	$ 2,586	$ 2,299	$ 7,618	$ 7,229