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

6 Months Ended

Jun. 30, 2023

Notes Tables

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

	June 30,		December 31,
	2023		2022
Cash	$	459,145	$	273,145
Money market funds		47,814		15,462
Certificates of deposit		124,043		130,467
Corporate debt securities		183,695		292,586
Commercial paper		11,376		17,928
U.S. treasuries and government agency bonds		114,413		8,285
Auction-rate securities backed by student-loan notes		649		1,711
Total	$	941,135	$	739,584

	June 30,		December 31,
	2023		2022
Reported as:
Cash and cash equivalents	$	506,959	$	288,607
Short-term investments		433,527		449,266
Investment within other long-term assets		649		1,711
Total	$	941,135	$	739,584

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	250,915	$	248,256
Due in 1 - 5 years		187,435		185,271
Due in greater than 5 years		650		649
Total	$	439,000	$	434,176

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

	June 30, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	47,814	$	-	$	-		$	47,814
Certificates of deposit		124,043		-		-			124,043
Corporate debt securities		187,961		1		(4,267	)		183,695
Commercial paper		11,376		-		-			11,376
U.S. treasuries and government agency bonds		114,970		11		(568	)		114,413
Auction-rate securities backed by student-loan notes		650		-		(1	)		649
Total	$	486,814	$	12	$	(4,836	)	$	481,990

	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]

	June 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	$	30,126	$	(103	)	$	151,567	$	(4,164	)	$	181,693	$	(4,267	)
U.S. treasuries and government agency bonds		106,771		(530	)		3,461		(38	)		110,232		(568	)
Auction-rate securities backed by student-loan notes		-		-			649		(1	)		649		(1	)
Total	$	136,897	$	(633	)	$	155,677	$	(4,203	)	$	292,574	$	(4,836	)

	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]

	June 30,		December 31,
	2023		2022
Cash and cash equivalents	$	506,959	$	288,607
Restricted cash included in other long-term assets		125		122
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$	507,084	$	288,729