Note 3 - Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	As at December 31, 2019
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	18,224	$	16	$	(11	)	$	18,229
		18,224		16		(11	)		18,229
Available-for-sale - matures after one year through five years:
Corporate bonds		46,593		168		(123	)		46,638
		46,593		168		(123	)		46,638
Total	$	64,817	$	184	$	(134	)	$	64,867

	As at December 31, 2018
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	6,094	$	—	$	(32	)	$	6,062
		6,094		—		(32	)		6,062
Available-for-sale - matures after one year through five years:
Certificate of deposits		747		—		—			747
Government bonds		501		—		(5	)		496
Corporate bonds		71,350		134		(1,320	)		70,164
		72,598		134		(1,325	)		71,407
Total	$	78,692	$	134	$	(1,357	)	$	77,469

Available-for-sale Securities, Continuous 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, 2019	$	22,852	$	(102	)	$	14,231	$	(32	)
As of December 31, 2018	$	16,580	$	(192	)	$	52,590	$	(1,165	)

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

	Year ended December 31,
	2017			201 8			201 9
Gross realized gains from sale of available-for-sale marketable securities	$	47		$	4		$	13
Gross realized losses from sale of available-for-sale marketable securities	$	(47	)	$	(71	)	$	(41	)