Note 5 - Investments, Available-for-sale (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

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

	December 31, 2023
	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value		Short-term investments
					(in thousands)
Corporate bonds	$	3,981	$	-	$	(10	)	$	3,971	$	3,971
Total investments	$	3,981	$	-	$	(10	)	$	3,971	$	3,971

	December 31, 2022
	Amortized Cost		Unrealized Gain		Unrealized Loss			Fair Value		Short-term investments		Long-term investments
					(in thousands)
Commercial paper	$	12,364	$	-	$	(49	)	$	12,315	$	12,315	$	-
Corporate bonds		55,201		-		(447	)		54,754		50,889		3,865
U.S. government agencies		999		-		(8	)		991		991		-
Total investments	$	68,564	$	-	$	(504	)	$	68,060	$	64,195	$	3,865

Investments Classified by Contractual Maturity Date [Table Text Block]

	December 31, 2023
	Amortized Cost		Fair Value
	(in thousands)
Mature in less than one year	$	3,981	$	3,971
Total	$	3,981	$	3,971