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

3 Months Ended

Mar. 31, 2019

Notes Tables

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

	March 31,		December 31,
	2019		2018
Cash, cash equivalents and investments:
Cash	$	125,687	$	131,569
Money market funds		56,082		41,135
Corporate debt securities		143,453		170,909
U.S. treasuries and government agency bonds		32,202		32,068
Certificates of deposit		1,600		1,600
Auction-rate securities backed by student-loan notes		3,290		3,241
Total	$	362,314	$	380,522

	March 31,		December 31,
	2019		2018
Reported as:
Cash and cash equivalents	$	181,769	$	172,704
Short-term investments		177,255		204,577
Long-term investments		3,290		3,241
Total	$	362,314	$	380,522

Investments Classified by Contractual Maturity Date [Table Text Block]

	March 31,		December 31,
	2019		2018
Due in less than 1 year	$	119,617	$	125,845
Due in 1 - 5 years		57,638		78,732
Due in greater than 5 years		3,290		3,241
Total	$	180,545	$	207,818

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

	March 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Total Fair Value		Fair Value of Investments in Unrealized Loss Position
Money market funds	$	56,082	$	-	$	-		$	56,082	$	-
Corporate debt securities		144,041		44		(632	)		143,453		123,828
U.S. treasuries and government agency bonds		32,257		10		(65	)		32,202		22,879
Certificates of deposit		1,600		-		-			1,600		-
Auction-rate securities backed by student-loan notes		3,570		-		(280	)		3,290		3,290
Total	$	237,550	$	54	$	(977	)	$	236,627	$	149,997

	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]

	March 31,		December 31,
	2019		2018
Cash and cash equivalents	$	181,769	$	172,704
Restricted cash included in other long-term assets		113		114
Total cash, cash equivalents and restricted cash reported in the Condensed Consolidated Statements of Cash Flows	$	181,882	$	172,818