Note 7 - Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2021

Notes Tables

Debt Securities, Available-for-sale [Table Text Block]

	September 30, 2021
(in thousands)	Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. municipal securities	$	18,515	$	28	$	(13	)	$	18,530
Corporate debt securities		11,852		34		(14	)		11,872
U.S. government agency securities		1,500		-		(1	)		1,499
Certificates of deposit/time deposits		4,160		38		-			4,198
Total marketable securities	$	36,027	$	100	$	(28	)	$	36,099

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

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

Investments Classified by Contractual Maturity Date [Table Text Block]

	September 30,
(in thousands)	2021
Due in one year or less	$	16,542
Due after one year through five years		19,557
Total marketable securities	$	36,099