Note 9 - Cash, Cash Equivalents and Investments (Tables)

6 Months Ended

Jun. 30, 2015

Disclosure Text Block Supplement [Abstract]

Fair Value, by Balance Sheet Grouping [Table Text Block]

	June 30,		December 31,
	2015		2014
Cash, cash equivalents and investments:
Cash	$	46,179	$	66,188
Money market funds		34,689		60,078
Certificates of deposit		23,093		22,778
U.S. treasuries and government agency bonds		127,073		89,674
Auction-rate securities backed by student-loan notes		5,375		5,389
Total	$	236,409	$	244,107

	June 30,		December 31,
Reported as:	2015		2014
Cash and cash equivalents	$	80,868	$	126,266
Short-term investments		150,166		112,452
Long-term investments		5,375		5,389
Total	$	236,409	$	244,107

Investments Classified by Contractual Maturity Date [Table Text Block]

	June 30,		December 31,
	2015		2014
Due in less than 1 year	$	118,344	$	91,335
Due in 1 - 5 years		31,822		21,117
Due in greater than 5 years		5,375		5,389
Total	$	155,541	$	117,841

Unrealized Gain (Loss) on Investments [Table Text Block]

	As of June 30, 2015
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	34,689	$	-	$	-		$	34,689	$	-
Certificates of deposit		23,093		-		-			23,093		-
U.S. treasuries and government agency bonds		127,053		39		(19	)		127,073		45,644
Auction-rate securities backed by student-loan notes		5,570		-		(195	)		5,375		5,375
Total	$	190,405	$	39	$	(214	)	$	190,230	$	51,019

	As of December 31, 2014
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	60,078	$	-	$	-		$	60,078	$	-
Certificates of deposit		22,778		-		-			22,778		-
U.S. treasuries and government agency bonds		89,689		14		(29	)		89,674		35,062
Auction-rate securities backed by student-loan notes		5,570		-		(181	)		5,389		5,389
Total	$	178,115	$	14	$	(210	)	$	177,919	$	40,451