Note 8 - Cash, Cash Equivalents and Investments (Tables)

3 Months Ended

Mar. 31, 2017

Notes Tables

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

	March 31,		December 31,
	2017		2016
Cash, cash equivalents and investments:
Cash	$	68,552	$	87,747
Money market funds		8,274		24,956
Certificates of deposit		7,256		-
Corporate debt securities		170,389		109,644
U.S. treasuries and government agency bonds		24,170		45,877
Auction-rate securities backed by student-loan notes		5,342		5,354
Total	$	283,983	$	273,578

	March 31,		December 31,
	2017		2016
Reported as:
Cash and cash equivalents	$	76,826	$	112,703
Short-term investments		201,815		155,521
Long-term investments		5,342		5,354
Total	$	283,983	$	273,578

Investments Classified by Contractual Maturity Date [Table Text Block]

	March 31,		December 31,
	2017		2016
Due in less than 1 year	$	61,688	$	47,568
Due in 1 - 5 years		140,127		107,953
Due in greater than 5 years		5,342		5,354
Total	$	207,157	$	160,875

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

	March 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	8,274	$	-	$	-		$	8,274	$	-
Certificates of deposit		7,256		-		-			7,256		-
Corporate debt securities		170,959		75		(645	)		170,389		129,006
U.S. treasuries and government agency bonds		24,193		3		(26	)		24,170		21,180
Auction-rate securities backed by student-loan notes		5,570		-		(228	)		5,342		5,342
Total	$	216,252	$	78	$	(899	)	$	215,431	$	155,528

	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