Note 7 - Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

Debt Securities, Held-to-maturity [Table Text Block]

	December 31, 2020
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government agency securities	$	18,500	$	6	$	(10	)	$	18,496
Corporate debt securities		42,048		211		(11	)		42,248
U.S. municipal securities		25,003		83		(2	)		25,084
Commercial paper		2,499		-		-			2,499
Certificates of deposit/time deposits		5,395		93		-			5,488
Total marketable securities	$	93,445	$	393	$	(23	)	$	93,815

	December 31, 2019
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government agency securities	$	6,274	$	1	$	(7	)	$	6,268
Corporate debt securities		26,944		80		(12	)		27,012
U.S. municipal securities		10,204		9		(3	)		10,210
Commercial paper		3,491		-		-			3,491
Certificates of deposit/time deposits		1,484		22		-			1,506
Total marketable securities	$	48,397	$	112	$	(22	)	$	48,487

Investments Classified by Contractual Maturity Date [Table Text Block]

	December 31,
(in thousands)	2020
Due in one year or less	$	34,088
Due after one year through five years		59,357
Total marketable securities	$	93,445