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

9 Months Ended

Sep. 30, 2020

Notes Tables

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

	September 30,		December 31,
	2020		2019
Cash, cash equivalents and investments:
Cash	$	138,271	$	144,860
Money market funds		41,195		28,100
Corporate debt securities		349,342		260,950
Commercial paper		7,985		1,994
U.S. treasuries and government agency bonds		14,749		19,493
Auction-rate securities backed by student-loan notes		2,916		3,138
Total	$	554,458	$	458,535

	September 30,		December 31,
	2020		2019
Reported as:
Cash and cash equivalents	$	179,466	$	172,960
Short-term investments		372,076		282,437
Long-term investments		2,916		3,138
Total	$	554,458	$	458,535

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	156,119	$	156,891
Due in 1 - 5 years		212,464		215,185
Due in greater than 5 years		3,070		2,916
Total	$	371,653	$	374,992

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

	September 30, 2020
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	41,195	$	-	$	-		$	41,195
Corporate debt securities		345,865		3,590		(113	)		349,342
Commercial paper		7,970		15		-			7,985
U.S. treasuries and government agency bonds		14,748		3		(2	)		14,749
Auction-rate securities backed by student-loan notes		3,070		-		(154	)		2,916
Total	$	412,848	$	3,608	$	(269	)	$	416,187

	December 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	28,100	$	-	$	-		$	28,100
Corporate debt securities		260,645		383		(78	)		260,950
Commercial paper		1,994		-		-			1,994
U.S. treasuries and government agency bonds		19,487		7		(1	)		19,493
Auction-rate securities backed by student-loan notes		3,320		-		(182	)		3,138
Total	$	313,546	$	390	$	(261	)	$	313,675

Debt Securities, Available-for-sale, Unrealized Loss Position, Fair Value [Table Text Block]

	September 30, 2020
	Less than 12 Months					Greater than 12 Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate debt securities	$	60,921	$	(113	)	$	-	$	-		$	60,921	$	(113	)
U.S. treasuries and government agency bonds		4,997		(2	)		-		-			4,997		(2	)
Auction-rate securities backed by student-loan notes		-		-			2,916		(154	)		2,916		(154	)
Total	$	65,918	$	(115	)	$	2,916	$	(154	)	$	68,834	$	(269	)

	December 31, 2019
	Less than 12 Months					Greater than 12 Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate debt securities	$	82,126	$	(63	)	$	11,136	$	(15	)	$	93,262	$	(78	)
U.S. treasuries and government agency bonds		993		(1	)		-		-			993		(1	)
Auction-rate securities backed by student-loan notes		-		-			3,138		(182	)		3,138		(182	)
Total	$	83,119	$	(64	)	$	14,274	$	(197	)	$	97,393	$	(261	)

Restrictions on Cash and Cash Equivalents [Table Text Block]

	September 30,		December 31,
	2020		2019
Cash and cash equivalents	$	179,466	$	172,960
Restricted cash included in other long-term assets		122		116
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$	179,588	$	173,076