Note 8 - Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	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

	December 31, 2018
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government agency securities	$	16,843	$	-	$	(88	)	$	16,755
Corporate debt securities		31,769		-		(96	)		31,673
U.S. municipal securities		17,509		1		(33	)		17,477
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]

	December 31,
(in thousands)	2019
Due in one year or less	$	35,437
Due after one year through five years		12,960
Total marketable securities	$	48,397