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

3 Months Ended

Mar. 31, 2023

Notes Tables

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

	March 31,		December 31,
	2023		2022
Cash	$	447,746	$	273,145
Money market funds		41,226		15,462
Certificates of deposit		131,042		130,467
Corporate debt securities		244,155		292,586
Commercial paper		18,163		17,928
U.S. treasuries and government agency bonds		35,238		8,285
Auction-rate securities backed by student-loan notes		1,516		1,711
Total	$	919,086	$	739,584

	March 31,		December 31,
	2023		2022
Reported as:
Cash and cash equivalents	$	488,972	$	288,607
Short-term investments		428,598		449,266
Investment within other long-term assets		1,516		1,711
Total	$	919,086	$	739,584

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	252,449	$	249,803
Due in 1 - 5 years		181,774		178,795
Due in greater than 5 years		1,571		1,516
Total	$	435,794	$	430,114

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

	March 31, 2023
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	41,226	$	-	$	-		$	41,226
Certificates of deposit		131,042		-		-			131,042
Corporate debt securities		249,743		39		(5,627	)		244,155
Commercial paper		18,163		-		-			18,163
U.S. treasuries and government agency bonds		35,276		83		(121	)		35,238
Auction-rate securities backed by student-loan notes		1,570		-		(54	)		1,516
Total	$	477,020	$	122	$	(5,802	)	$	471,340

	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]

	March 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	$	18,084	$	(68	)	$	212,767	$	(5,559	)	$	230,851	$	(5,627	)
U.S. treasuries and government agency bonds		2,878		(5	)		7,383		(116	)		10,261		(121	)
Auction-rate securities backed by student-loan notes		-		-			1,516		(54	)		1,516		(54	)
Total	$	20,962	$	(73	)	$	221,666	$	(5,729	)	$	242,628	$	(5,802	)

	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]

	March 31,		December 31,
	2023		2022
Cash and cash equivalents	$	488,972	$	288,607
Restricted cash included in other long-term assets		123		122
Total cash, cash equivalents and restricted cash reported on the Condensed Consolidated Statements of Cash Flows	$	489,095	$	288,729