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

9 Months Ended

Sep. 30, 2022

Notes Tables

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

	September 30,		December 31,
	2022		2021
Cash	$	245,051	$	174,937
Money market funds		71,159		14,328
Certificates of deposit		126,532		141,478
Corporate debt securities		286,065		386,883
U.S. treasuries and government agency bonds		7,240		7,456
Auction-rate securities backed by student-loan notes		2,083		2,401
Total	$	738,130	$	727,483

	September 30,		December 31,
	2022		2021
Reported as:
Cash and cash equivalents	$	316,210	$	189,265
Short-term investments		419,837		535,817
Investment within other long-term assets		2,083		2,401
Total	$	738,130	$	727,483

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Due in less than 1 year	$	316,904	$	313,134
Due in 1 - 5 years		113,002		106,703
Due in greater than 5 years		2,195		2,083
Total	$	432,101	$	421,920

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

	September 30, 2022
	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	$	71,159	$	-	$	-		$	71,159
Certificates of deposit		126,532		-		-			126,532
Corporate debt securities		295,877		-		(9,812	)		286,065
U.S. treasuries and government agency bonds		7,497		-		(257	)		7,240
Auction-rate securities backed by student-loan notes		2,195		-		(112	)		2,083
Total	$	503,260	$	-	$	(10,181	)	$	493,079

	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]

	September 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	$	203,576	$	(6,236	)	$	81,489	$	(3,576	)	$	285,065	$	(9,812	)
U.S. treasuries and government agency bonds		3,361		(136	)		3,879		(121	)		7,240		(257	)
Auction-rate securities backed by student-loan notes		-		-			2,083		(112	)		2,083		(112	)
Total	$	206,937	$	(6,372	)	$	87,451	$	(3,809	)	$	294,388	$	(10,181	)

	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]

	September 30,		December 31,
	2022		2021
Cash and cash equivalents	$	316,210	$	189,265
Restricted cash included in other long-term assets		115		124
Total cash, cash equivalents and restricted cash reported on the Consolidated Statements of Cash Flows	$	316,325	$	189,389