Note 10 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2022

Notes Tables

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

	September 30, 2022
	Total		Level 1		Level 2		Level 3
Money market funds	$	71,159	$	71,159	$	-	$	-
Certificates of deposit		126,532		-		126,532		-
Corporate debt securities		286,065		-		286,065		-
U.S. treasuries and government agency bonds		7,240		-		7,240		-
Auction-rate securities backed by student-loan notes		2,083		-		-		2,083
Mutual funds and money market funds under deferred compensation plan		29,140		29,140		-		-
Total	$	522,219	$	100,299	$	419,837	$	2,083

	December 31, 2021
	Total		Level 1		Level 2		Level 3
Money market funds	$	14,328	$	14,328	$	-	$	-
Certificates of deposit		141,478		-		141,478		-
Corporate debt securities		386,883		-		386,883		-
U.S. treasuries and government agency bonds		7,456		-		7,456		-
Auction-rate securities backed by student-loan notes		2,401		-		-		2,401
Mutual funds and money market funds under deferred compensation plan		31,786		31,786		-		-
Total	$	584,332	$	46,114	$	535,817	$	2,401