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

9 Months Ended

Sep. 30, 2018

Notes Tables

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

	September 30,		December 31,
	2018		2017
Cash, cash equivalents and investments:
Cash	$	105,859	$	75,125
Money market funds		25,235		7,134
Corporate debt securities		190,924		203,807
U.S. treasuries and government agency bonds		24,230		13,024
Certificates of deposit		1,600		-
Auction-rate securities backed by student-loan notes		5,257		5,256
Total	$	353,105	$	304,346

	September 30,		December 31,
	2018		2017
Reported as:
Cash and cash equivalents	$	131,094	$	82,759
Short-term investments		216,754		216,331
Long-term investments		5,257		5,256
Total	$	353,105	$	304,346

Investments Classified by Contractual Maturity Date [Table Text Block]

	September 30,		December 31,
	2018		2017
Due in less than 1 year	$	111,908	$	89,399
Due in 1 - 5 years		104,846		126,932
Due in greater than 5 years		5,257		5,256
Total	$	222,011	$	221,587

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

	September 30, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	25,235	$	-	$	-		$	25,235	$	-
Corporate debt securities		192,581		2		(1,659	)		190,924		187,359
U.S. treasuries and government agency bonds		24,419		-		(189	)		24,230		24,230
Certificates of deposit		1,600		-		-			1,600		-
Auction-rate securities backed by student-loan notes		5,570		-		(313	)		5,257		5,257
Total	$	249,405	$	2	$	(2,161	)	$	247,246	$	216,846

	December 31, 2017
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	7,134	$	-	$	-		$	7,134	$	-
Corporate debt securities		204,789		17		(999	)		203,807		197,564
U.S. treasuries and government agency bonds		13,092		-		(68	)		13,024		13,024
Auction-rate securities backed by student-loan notes		5,570		-		(314	)		5,256		5,256
Total	$	230,585	$	17	$	(1,381	)	$	229,221	$	215,844

Restrictions on Cash and Cash Equivalents [Table Text Block]

	September 30,		December 31,
	2018		2017
Cash and cash equivalents	$	131,094	$	82,759
Restricted cash included in other long-term assets		115		115
Total cash, cash equivalents and restricted cash shown in the Condensed Consolidated Statements of Cash Flows	$	131,209	$	82,874