Note 5 - Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

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

	March 3 1 , 20 20 (Unaudited)
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	17,049	$	35	$	(155	)	$	16,929
		17,049		35		(155	)		16,929
Available-for-sale - matures after one year through five years:
Corporate bonds		51,586		195		(801	)		50,980
		51,586		195		(801	)		50,980
Total	$	68,635	$	230	$	(956	)	$	67,909

	December 31, 201 9
	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

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 March 31, 2020 (unaudited)	$	29,663	$	(820	)	$	8,219	$	(136	)
As of December 31, 2019	$	22,852	$	(102	)	$	14,231	$	(32	)

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

	Three months ended March 3 1 ,
	20 20 (unaudited)			201 9 (unaudited)
Gross realized gains from sale of available-for-sale marketable securities	$	4		$	—
Gross realized losses from sale of available-for-sale marketable securities	$	(6	)	$	(24	)