Note 5 - Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2019

Notes Tables

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

	March 3 1 , 201 9 (Unaudited)
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	9,358	$	2	$	(46	)	$	9,314
		9,358		2		(46	)		9,314
Available-for-sale - matures after one year through five years:
Certificate of deposits		747		—		—			747
Government bonds		501		—		(3	)		498
Corporate bonds		67,541		129		(642	)		67,028
		68,789		129		(645	)		68,273
Total	$	78,147	$	131	$	(691	)	$	77,587

	December 31, 201 8
	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 March 31, 2019 (unaudited)	$	12,359	$	(141	)	$	51,257	$	(550	)
As of December 31, 2018	$	16,580	$	(192	)	$	52,590	$	(1,165	)

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

	Three months ended March 3 1 ,
	201 9 (unaudited)			201 8 (unaudited)
Gross realized gains from sale of available-for-sale marketable securities	$	—		$	4
Gross realized losses from sale of available-for-sale marketable securities	$	(24	)	$	—