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

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	December 31,
	2016		2015
Cash, cash equivalents and investments:
Cash	$	87,747	$	58,217
Money market funds		24,956		31,640
Certificates of deposit		-		21,574
Corporate debt securities		109,644		-
U.S. treasuries and government agency bonds		45,877		123,532
Auction-rate securities backed by student-loan notes		5,354		5,361
Total	$	273,578	$	240,324

	December 31,
	2016		2015
Reported as:
Cash and cash equivalents	$	112,703	$	90,860
Short-term investments		155,521		144,103
Long-term investments		5,354		5,361
Total	$	273,578	$	240,324

Investments Classified by Contractual Maturity Date [Table Text Block]

	December 31,
	2016		2015
Due in less than 1 year	$	47,568	$	110,898
Due in 1 - 5 years		107,953		33,205
Due in greater than 5 years		5,354		5,361
Total	$	160,875	$	149,464

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

	December 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	24,956	$	-	$	-		$	24,956	$	-
Corporate debt securities		110,429		65		(850	)		109,644		91,938
U.S. treasuries and government agency bonds		45,899		-		(22	)		45,877		39,275
Auction-rate securities backed by student-loan notes		5,570		-		(216	)		5,354		5,354
Total	$	186,854	$	65	$	(1,088	)	$	185,831	$	136,567

	December 31, 2015
	Amortized 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