Note 5 - Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2022

Notes Tables

Schedule of Available-for-Sale Securities Reconciliation [Table Text Block]

	June 30, 2022 (Unaudited)
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	8,756	$	2	$	(23	)	$	8,735
Available-for-sale - matures after one year through five years:
Corporate bonds		99,386		—		(5,149	)		94,237
Total
	$	108,142	$	2	$	(5,172	)	$	102,972

	December 31, 2021
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	11,937	$	39	$	(7	)	$	11,969
Available-for-sale - matures after one year through five years:
Corporate bonds		78,920		227		(818	)		78,329
Total	$	90,857	$	266	$	(825	)	$	90,298

Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block]

	Less than 12 months					12 months or greater
	Fair value		Gross unrealized loss			Fair value		Gross unrealized loss
As of June 30, 2022 (unaudited)	$	82,144	$	(3,264	)	$	20,328	$	(1,908	)
As of December 31, 2021	$	53,412	$	(667	)	$	12,039	$	(158	)

Schedule of Realized Gain (Loss) [Table Text Block]

	Six months ended June 30,						Three months ended June 30,
	2022 (unaudited)			2021 (unaudited)			2022 (unaudited)			2021 (unaudited)
Gross realized gains from sale of available-for-sale marketable securities	$	—		$	43		$	—		$	43
Gross realized losses from sale of available-for-sale marketable securities	$	(21	)	$	(28	)	$	(21	)	$	(28	)