Note 7 - Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2015

Notes Tables

Held-to-maturity Securities [Table Text Block]

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

	December 31, 2014
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
U.S. government agency securities	$	20,048	$	-	$	(71	)	$	19,977
Corporate debt securities		29,316		7		(79	)		29,244
U.S. municipal securities		30,004		32		(18	)		30,018
Certificates of deposit/time deposits		5,656		5		(15	)		5,646
Total marketable securities	$	85,024	$	44	$	(183	)	$	84,885

Investments Classified by Contractual Maturity Date [Table Text Block]

	December 31,
(in thousands)	2015
Due in one year or less	$	33,201
Due after one year through five years		64,789
Total marketable securities	$	97,990