Note 5 - Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2019

Notes Tables

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

	June 3 0 , 201 9 (Unaudited)
	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair value
Available-for-sale - matures within one year:
Corporate bonds	$	14,334	$	3	$	(41	)	$	14,296
		14,334		3		(41	)		14,296
Available-for-sale - matures after one year through five years:
Certificate of deposits		747		—		—			747
Government bonds		501		—		(1	)		500
Corporate bonds		60,505		265		(190	)		60,580
		61,753		265		(191	)		61,827
Total	$	76,087	$	268	$	(232	)	$	76,123

	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 June 30, 2019 (unaudited)	$	1,197	$	(3	)	$	51,975	$	(229	)
As of December 31, 2018	$	16,580	$	(192	)	$	52,590	$	(1,165	)

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

	Six months ended June 3 0 ,						Three months ended June 3 0 ,
	201 9 (unaudited)			201 8 (unaudited)			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	$	(35	)	$	(2	)	$	(11	)	$	(2	)