Note 5 - Financial Instruments Measured at Fair Value (Tables)

6 Months Ended

Jul. 01, 2023

Notes Tables

Unrealized Gain (Loss) on Investments [Table Text Block]

	July 1, 2023
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	40,643	$	5	$	113	$	40,535
Bank certificates of deposit		21,250		4		21		21,233
U.S. treasury securities		21,179		-		323		20,856
Asset-backed securities		10,644		-		55		10,589
Government-sponsored enterprise securities		2,980		1		-		2,981
Foreign government security		833		-		-		833
	$	97,529	$	10	$	512	$	97,027

	December 31, 2022
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	59,283	$	30	$	240	$	59,073
Bank certificates of deposit		36,500		20		41		36,479
U.S. treasury securities		34,614		1		418		34,197
Asset-backed securities		12,727		10		79		12,658
Foreign government security		828		-		-		828
	$	143,952	$	61	$	778	$	143,235

Investments Classified by Contractual Maturity Date [Table Text Block]

	July 1, 2023				December 31, 2022
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
Due in one year or less	$	79,210	$	78,793	$	112,956	$	112,683
Due after one year through three years		18,319		18,234		30,996		30,552
	$	97,529	$	97,027	$	143,952	$	143,235

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

	Fair value measurements at July 1, 2023 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	150,874	$	-	$	-	$	150,874
U.S. treasury securities		-		23,342		-		23,342
Corporate debt securities		-		49,419		-		49,419
Asset-backed securities		-		10,590		-		10,590
Government-sponsored enterprise securities		-		2,981		-		2,981
Money market funds		-		113,045		-		113,045
Bank certificates of deposit		-		21,233		-		21,233
Foreign government security		-		833		-		833
	$	150,874	$	221,443	$	-	$	372,317

	Fair value measurements at December 31, 2022 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	190,371	$	-	$	-	$	190,371
Corporate debt securities		-		69,753		-		69,753
Money market funds		-		40,290		-		40,290
Bank certificates of deposit		-		37,480		-		37,480
U.S. treasury securities		-		34,196		-		34,196
Asset-backed securities		-		12,658		-		12,658
Foreign government security		-		828		-		828
	$	190,371	$	195,205	$	-	$	385,576