Note 3 - Cash, Cash Equivalents and Investments (Tables)

12 Months Ended

Dec. 31, 2015

Disclosure Text Block Supplement [Abstract]

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

	December 31,
	2015		2014
Cash, cash equivalents and investments:
Cash	$	58,217	$	66,188
Money market funds		31,640		60,078
Certificates of deposit		21,574		22,778
U.S. treasuries and government agency bonds		123,532		89,674
Auction-rate securities backed by student-loan notes		5,361		5,389
Total	$	240,324	$	244,107

	December 31,
Reported as:	2015		2014
Cash and cash equivalents	$	90,860	$	126,266
Short-term investments		144,103		112,452
Long-term investments		5,361		5,389
Total	$	240,324	$	244,107

Investments Classified by Contractual Maturity Date [Table Text Block]

	December 31,
	2015		2014
Due in less than 1 year	$	110,898	$	91,335
Due in 1 - 5 years		33,205		21,117
Due in greater than 5 years		5,361		5,389
Total	$	149,464	$	117,841

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

	December 31, 2015
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	31,640	$	-	$	-		$	31,640	$	-
Certificates of deposit		21,574		-		-			21,574		-
U.S. treasuries and government agency bonds		123,698		4		(170	)		123,532		110,720
Auction-rate securities backed by student-loan notes		5,570		-		(209	)		5,361		5,361
Total	$	182,482	$	4	$	(379	)	$	182,107	$	116,081

	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