Note 10 - Cash, Cash Equivalents, Investments and Restricted Cash (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

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

	September 30,		December 31,
	2019		2018
Cash, cash equivalents and investments:
Cash	$	162,741	$	131,569
Money market funds		39,982		41,135
Corporate debt securities		195,667		170,909
U.S. treasuries and government agency bonds		20,350		32,068
Certificates of deposit		-		1,600
Auction-rate securities backed by student-loan notes		3,264		3,241
Total	$	422,004	$	380,522

	September 30,		December 31,
	2019		2018
Reported as:
Cash and cash equivalents	$	205,229	$	172,704
Short-term investments		213,511		204,577
Long-term investments		3,264		3,241
Total	$	422,004	$	380,522

Investments Classified by Contractual Maturity Date [Table Text Block]

	September 30,		December 31,
	2019		2018
Due in less than 1 year	$	142,336	$	125,845
Due in 1 - 5 years		71,175		78,732
Due in greater than 5 years		3,264		3,241
Total	$	216,775	$	207,818

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

	September 30, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	39,982	$	-	$	-		$	39,982	$	-
Corporate debt securities		195,471		324		(128	)		195,667		83,247
U.S. treasuries and government agency bonds		20,341		11		(2	)		20,350		7,998
Auction-rate securities backed by student-loan notes		3,445		-		(181	)		3,264		3,264
Total	$	259,239	$	335	$	(311	)	$	259,263	$	94,509

	December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	41,135	$	-	$	-		$	41,135	$	-
Corporate debt securities		172,288		7		(1,386	)		170,909		166,204
U.S. treasuries and government agency bonds		32,207		2		(141	)		32,068		28,507
Certificates of deposit		1,600		-		-			1,600		-
Auction-rate securities backed by student-loan notes		3,570		-		(329	)		3,241		3,241
Total	$	250,800	$	9	$	(1,856	)	$	248,953	$	197,952

Restrictions on Cash and Cash Equivalents [Table Text Block]

	September 30,		December 31,
	2019		2018
Cash and cash equivalents	$	205,229	$	172,704
Restricted cash included in other current assets		1,161		-
Restricted cash included in other long-term assets		113		114
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$	206,503	$	172,818