Note 6 - Employee Benefit Plans - Reported Share-based Compensation in Consolidated Financial Statements (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Share-based compensation of continuing operations	$ 14,234	$ 14,148	$ 10,053
Income tax benefit	(963)	(587)	(993)
Total share-based compensation, net of tax	13,271	13,561	9,060
Cost of Sales [Member]
Share-based compensation of continuing operations	893	736	546
Research and Development Expense [Member]
Share-based compensation of continuing operations	3,245	2,994	1,717
Selling, General and Administrative Expenses [Member]
Share-based compensation of continuing operations	$ 10,096	$ 10,418	$ 7,790

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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