Note 3 - Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

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

	As at December 31, 2022
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	17,552	$	—	$	(1,330	)	$	16,222
Available-for-sale - matures after one year through five years:
Corporate bonds		101,355		38		(5,535	)		95,858
Total	$	118,907	$	38	$	(6,865	)	$	112,080

	As at 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 December 31, 2022	$	58,706	$	(1,885	)	$	48,539	$	(4,980	)
As of December 31, 2021	$	53,412	$	(667	)	$	12,039	$	(158	)

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

	Year ended December 31,
	2020			2021			2022
Gross realized gains from sale of available-for-sale marketable securities	$	14		$	43		$	—
Gross realized losses from sale of available-for-sale marketable securities	$	(20	)	$	(30	)	$	(55	)