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

6 Months Ended

Jun. 30, 2022

Notes Tables

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

	June 30,		December 31,
	2022		2021
Cash	$	274,475	$	174,937
Money market funds		68,392		14,328
Certificates of deposit		134,374		141,478
Corporate debt securities		327,358		386,883
U.S. treasuries and government agency bonds		7,280		7,456
Auction-rate securities backed by student-loan notes		2,219		2,401
Total	$	814,098	$	727,483

	June 30,		December 31,
	2022		2021
Reported as:
Cash and cash equivalents	$	342,867	$	189,265
Short-term investments		469,012		535,817
Investment within other long-term assets		2,219		2,401
Total	$	814,098	$	727,483

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	275,261	$	273,257
Due in 1 - 5 years		202,543		195,755
Due in greater than 5 years		2,320		2,219
Total	$	480,124	$	471,231

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

	June 30, 2022
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	68,392	$	-	$	-		$	68,392
Certificates of deposit		134,374		-		-			134,374
Corporate debt securities		335,934		9		(8,585	)		327,358
U.S. treasuries and government agency bonds		7,496		-		(216	)		7,280
Auction-rate securities backed by student-loan notes		2,320		-		(101	)		2,219
Total	$	548,516	$	9	$	(8,902	)	$	539,623

	December 31, 2021
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	14,328	$	-	$	-		$	14,328
Certificates of deposit		141,478		-		-			141,478
Corporate debt securities		388,081		570		(1,768	)		386,883
U.S. treasuries and government agency bonds		7,495		-		(39	)		7,456
Auction-rate securities backed by student-loan notes		2,520		-		(119	)		2,401
Total	$	553,902	$	570	$	(1,926	)	$	552,546

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

	June 30, 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	$	284,630	$	(7,859	)	$	33,521	$	(726	)	$	318,151	$	(8,585	)
U.S. treasuries and government agency bonds		7,280		(216	)		-		-			7,280		(216	)
Auction-rate securities backed by student-loan notes		-		-			2,219		(101	)		2,219		(101	)
Total	$	291,910	$	(8,075	)	$	35,740	$	(827	)	$	327,650	$	(8,902	)

	December 31, 2021
	Less than 12 Months					Greater than 12 Months					Total
	Fair Value		Unrealized Losses			Fair Value		Unrealized Losses			Fair Value		Unrealized Losses
Corporate debt securities	$	285,954	$	(1,765	)	$	4,760	$	(3	)	$	290,714	$	(1,768	)
U.S. treasuries and government agency bonds		7,456		(39	)		-		-			7,456		(39	)
Auction-rate securities backed by student-loan notes		-		-			2,401		(119	)		2,401		(119	)
Total	$	293,410	$	(1,804	)	$	7,161	$	(122	)	$	300,571	$	(1,926	)

Restrictions on Cash and Cash Equivalents [Table Text Block]

	June 30,		December 31,
	2022		2021
Cash and cash equivalents	$	342,867	$	189,265
Restricted cash included in other long-term assets		118		124
Total cash, cash equivalents and restricted cash reported on the Consolidated Statements of Cash Flows	$	342,985	$	189,389