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

6 Months Ended

Jun. 30, 2018

Notes Tables

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

	June 30,		December 31,
	2018		2017
Cash, cash equivalents and investments:
Cash	$	66,994	$	75,125
Money market funds		16,081		7,134
Corporate debt securities		207,461		203,807
U.S. treasuries and government agency bonds		22,967		13,024
Auction-rate securities backed by student-loan notes		5,247		5,256
Total	$	318,750	$	304,346

	June 30,		December 31,
	2018		2017
Reported as:
Cash and cash equivalents	$	83,075	$	82,759
Short-term investments		230,428		216,331
Long-term investments		5,247		5,256
Total	$	318,750	$	304,346

Investments Classified by Contractual Maturity Date [Table Text Block]

	June 30,		December 31,
	2018		2017
Due in less than 1 year	$	109,345	$	89,399
Due in 1 - 5 years		121,083		126,932
Due in greater than 5 years		5,247		5,256
Total	$	235,675	$	221,587

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

	June 30, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	16,081	$	-	$	-		$	16,081	$	-
Corporate debt securities		209,385		10		(1,934	)		207,461		203,215
U.S. treasuries and government agency bonds		23,129		-		(162	)		22,967		22,967
Auction-rate securities backed by student-loan notes		5,570		-		(323	)		5,247		5,247
Total	$	254,165	$	10	$	(2,419	)	$	251,756	$	231,429

	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]

	June 30,		December 31,
	2018		2017
Cash and cash equivalents	$	83,075	$	82,759
Restricted cash included in other long-term assets		113		115
Total cash, cash equivalents and restricted cash shown in the Condensed Consolidated Statements of Cash Flows	$	83,188	$	82,874