Note 6 - Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

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

	September 30, 2019
(in thousands)	Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. municipal securities	$	5,612	$	11	$	(3	)	$	5,620
Corporate debt securities		16,503		100		(1	)		16,602
U.S. government agency securities		8,340		1		(10	)		8,331
Certificates of deposit/time deposits		1,479		22		(1	)		1,500
Commercial paper		1,491		-		(1	)		1,490
Total marketable securities	$	33,425	$	134	$	(16	)	$	33,543

	December 31, 2018
(in thousands)	Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. municipal securities	$	17,509	$	1	$	(33	)	$	17,477
Corporate debt securities		31,769		-		(96	)		31,673
U.S. government agency securities		16,843		-		(88	)		16,755
Certificates of deposit/time deposits		4,208		-		(25	)		4,183
Total marketable securities	$	70,329	$	1	$	(242	)	$	70,088

Investments Classified by Contractual Maturity Date [Table Text Block]

	September 30,
(in thousands)	2019
Due in one year or less	$	23,642
Due after one year through five years		9,783
Total marketable securities	$	33,425