Note 4 - Financial Instruments Measured at Fair Value (Tables)

12 Months Ended

Dec. 30, 2017

Notes Tables

Available-for-sale Securities [Table Text Block]

	At December 30, 2017
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	12,784	$	1	$	6	$	12,779
U.S. treasury securities		7,935		-		4		7,931
Foreign government security		619		-		-		619
	$	21,338	$	1	$	10	$	21,329

	At December 31, 2016
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses		Value
Foreign government security	$	623	$	-	$	-	$	623
Corporate debt securities (2)		22,513		1		6		22,508
Government-sponsored enterprise securities		8,109		-		1		8,108
Bank certificates of deposit		750		1		-		751
	$	31,995	$	2	$	7	$	31,990

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized		Estimated
(in thousands)	Cost		Fair Value
Due in one year or less	$	21,338	$	21,329

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

	Fair value measurements at December 30, 2017 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	100,850	$	-	$	-	$	100,850
Money market funds		-		22,205		-		22,205
Corporate debt securities		-		22,014		-		22,014
U.S. treasury securities		-		8,431		-		8,431
Government-sponsored enterprise securities		-		1,496		-		1,496
Foreign government security		-		619		-		619
	$	100,850	$	54,765	$	-	$	155,615

	Fair value measurements at December 31, 2016 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	70,279	$	-	$	-	$	70,279
Money market funds		-		24,166		-		24,166
Corporate debt securities		-		24,108		-		24,108
Government-sponsored enterprise securities		-		8,108		-		8,108
Foreign government security		-		623		-		623
Bank certificates of deposit		-		751		-		751
	$	70,279	$	57,756	$	-	$	128,035