Note 6 - Marketable Securities (Tables)

9 Months Ended

Sep. 30, 2016

Notes Tables

Held-to-maturity Securities [Table Text Block]

	September 30, 2016
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. municipal securities	$	42,718	$	7	$	(76	)	$	42,649
Corporate debt securities		32,745		18		(33	)		32,730
U.S. government agency securities		24,770		4		(25	)		24,749
Certificates of deposit/time deposits		7,182		32		-			7,214
Total marketable securities	$	107,415	$	61	$	(134	)	$	107,342

	December 31, 2015
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. municipal securities	$	35,667	$	8	$	(56	)	$	35,619
Corporate debt securities		28,133		-		(114	)		28,019
U.S. government agency securities		26,784		2		(99	)		26,687
Certificates of deposit/time deposits		5,909		2		(11	)		5,900
Commercial paper		1,497		-		(2	)		1,495
Total marketable securities	$	97,990	$	12	$	(282	)	$	97,720

Investments Classified by Contractual Maturity Date [Table Text Block]

	September 30,
(in thousands)	2016
Due in one year or less	$	39,028
Due after one year through five years		68,387
Total marketable securities	$	107,415