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

3 Months Ended

Apr. 01, 2023

Notes Tables

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

	April 1, 2023
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	36,670	$	23	$	149	$	36,544
Bank certificates of deposit		24,500		11		23		24,488
U.S. treasury securities		23,137		47		286		22,898
Asset-backed securities		12,932		-		64		12,868
Foreign government security		848		-		-		848
	$	98,087	$	81	$	522	$	97,646

	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]

	April 1, 2023				December 31, 2022
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
Due in one year or less	$	66,392	$	66,139	$	112,956	$	112,683
Due after one year through three years		31,695		31,507		30,996		30,552
	$	98,087	$	97,646	$	143,952	$	143,235

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

	Fair value measurements at April 1, 2023 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	166,925	$	-	$	-	$	166,925
U.S. treasury securities		-		29,886		-		29,886
Corporate debt securities		-		39,282		-		39,282
Asset-backed securities		-		12,869		-		12,869
Money market funds		-		49,998		-		49,998
Bank certificates of deposit		-		24,487		-		24,487
Foreign government security		-		848		-		848
	$	166,925	$	157,370	$	-	$	324,295

	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