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

9 Months Ended

Sep. 30, 2023

Notes Tables

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

	September 30,		December 31,
	2023		2022
Cash	$	377,324	$	273,145
Money market funds		43,854		15,462
Certificates of deposit		123,368		130,467
Corporate debt securities		130,614		292,586
Commercial paper		4,976		17,928
U.S. treasuries and government agency bonds		362,165		8,285
Auction-rate securities backed by student-loan notes		600		1,711
Total	$	1,042,901	$	739,584

	September 30,		December 31,
	2023		2022
Reported as:
Cash and cash equivalents	$	421,178	$	288,607
Short-term investments		621,123		449,266
Investment within other long-term assets		600		1,711
Total	$	1,042,901	$	739,584

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	405,120	$	403,201
Due in 1 - 5 years		219,510		217,922
Due in greater than 5 years		600		600
Total	$	625,230	$	621,723

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

	September 30, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Money market funds	$	43,854	$	-	$	-	$	43,854
Certificates of deposit		123,368		-		-		123,368
Corporate debt securities		133,442		3		(2,831)		130,614
Commercial paper		4,976		-		-		4,976
U.S. treasuries and government agency bonds		362,844		17		(696)		362,165
Auction-rate securities backed by student-loan notes		600		-		-		600
Total	$	669,084	$	20	$	(3,527)	$	665,577

	December 31, 2022
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	15,462	$	-	$	-		$	15,462
Certificates of deposit		130,467		-		-			130,467
Corporate debt securities		300,529		18		(7,961	)		292,586
Commercial paper		17,928		-		-			17,928
U.S. treasuries and government agency bonds		8,487		-		(202	)		8,285
Auction-rate securities backed by student-loan notes		1,770		-		(59	)		1,711
Total	$	474,643	$	18	$	(8,222	)	$	466,439

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

	September 30, 2023
	Less than 12 Months					Greater than 12 Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate debt securities	$	29,476	$	(79	)	$	97,133	$	(2,752	)	$	126,609	$	(2,831	)
U.S. treasuries and government agency bonds		237,004		(693	)		1,497		(3	)		238,501		(696	)
Auction-rate securities backed by student-loan notes		-		-			600		-			600		-
Total	$	266,480	$	(772	)	$	99,230	$	(2,755	)	$	365,710	$	(3,527	)

	December 31, 2022
	Less than 12 Months					Greater than 12 Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate debt securities	$	72,943	$	(973	)	$	202,074	$	(6,988	)	$	275,017	$	(7,961	)
U.S. treasuries and government agency bonds		987		(2	)		7,298		(200	)		8,285		(202	)
Auction-rate securities backed by student-loan notes		-		-			1,711		(59	)		1,711		(59	)
Total	$	73,930	$	(975	)	$	211,083	$	(7,247	)	$	285,013	$	(8,222	)

Restrictions on Cash and Cash Equivalents [Table Text Block]

	September 30,		December 31,
	2023		2022
Cash and cash equivalents	$	421,178	$	288,607
Restricted cash included in other long-term assets		122		122
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$	421,300	$	288,729