Note 7 - Financial Instruments Measured at Fair Value (Tables)

12 Months Ended

Dec. 26, 2020

Notes Tables

Available-for-sale Securities [Table Text Block]

	At December 26, 2020
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	14,943	$	2	$	1	$	14,944
U.S. treasury securities		2,012		-		-		2,012
Government-sponsored enterprise securities		1,998		-		-		1,998
Bank certificates of deposit		750		-		-		750
Foreign government security		965		-		-		965
	$	20,668	$	2	$	1	$	20,669

	At December 28, 2019
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Foreign government security	$	904	$	-	$	-	$	904

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized		Estimated
(in thousands)	Cost		Fair Value
Due in one year or less	$	20,668	$	20,669

Fair Value, Assets Measured on Recurring Basis [Table Text Block]

	Fair value measurements at December 26, 2020 using:
							Total Estimated
	Level 1		Level 2		Level 3		Fair Value
Cash	$	128,874	$	-	$	-	$	128,874
Money market funds		-		19,734		-		19,734
Foreign government security		-		965		-		965
Corporate debt securities		-		15,694		-		15,694
U.S. treasury securities		-		2,012		-		2,012
Government-sponsored enterprise securities		-		1,998		-		1,998
Bank certificates of deposit		-		750		-		750
	$	128,874	$	41,153	$	-	$	170,027

	Fair value measurements at December 28, 2019 using:
							Total Estimated
	Level 1		Level 2		Level 3		Fair Value
Cash	$	147,523	$	-	$	-	$	147,523
Money market funds		-		7,671		-		7,671
Foreign government security		-		904		-		904
	$	147,523	$	8,575	$	-	$	156,098