Note 3 - Cash, Cash Equivalents, Investments and Restricted Cash (Tables)

12 Months Ended

Dec. 31, 2023

Notes Tables

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

	December 31,
	2023		2022
Cash	$	392,329	$	273,145
Money market funds		135,514		15,462
Certificates of deposit		127,123		130,467
Corporate debt securities		95,101		292,586
Commercial paper		-		17,928
U.S. treasuries and government agency bonds		358,409		8,285
Auction-rate securities backed by student-loan notes		567		1,711
Total	$	1,109,043	$	739,584

	December 31,
	2023		2022
Reported as:
Cash and cash equivalents	$	527,843	$	288,607
Short-term investments		580,633		449,266
Investment within other long-term assets		567		1,711
Total	$	1,109,043	$	739,584

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	398,670	$	397,884
Due in 1 - 5 years		183,266		182,749
Due in greater than 5 years		574		567
Total	$	582,510	$	581,200

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

	December 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	135,514	$	-	$	-		$	135,514
Certificates of deposit		127,123		-		-			127,123
Corporate debt securities		96,636		4		(1,539	)		95,101
U.S. treasuries and government agency bonds		358,177		327		(95	)		358,409
Auction-rate securities backed by student-loan notes		574		-		(7	)		567
Total	$	718,024	$	331	$	(1,641	)	$	716,714

	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]

	December 31, 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	$	20,792	$	(19	)	$	70,806	$	(1,520	)	$	91,598	$	(1,539	)
U.S. treasuries and government agency bonds		97,599		(95	)		-		-			97,599		(95	)
Auction-rate securities backed by student-loan notes		-		-			567		(7	)		567		(7	)
Total	$	118,391	$	(114	)	$	71,373	$	(1,527	)	$	189,764	$	(1,641	)

	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]

	December 31,
	2023		2022
Cash and cash equivalents	$	527,843	$	288,607
Restricted cash included in other current assets		33,204		-
Restricted cash included in other long-term assets		134		122
Total cash, cash equivalents and restricted cash reported on the Consolidated Statements of Cash Flows	$	561,181	$	288,729