Note 11 - Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2024

Notes Tables

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

	June 30, 2024
	Total		Level 1		Level 2		Level 3
Money market funds	$	192,732	$	192,732	$	-	$	-
Certificates of deposit		165,120		-		165,120		-
Corporate debt securities		22,729		-		22,729		-
U.S. treasuries and government agency bonds		568,921		-		568,921		-
Auction-rate securities backed by student-loan notes		345		-		-		345
Mutual funds and money market funds under deferred compensation plan		58,928		58,928		-		-
Total	$	1,008,775	$	251,660	$	756,770	$	345

	December 31, 2023
	Total		Level 1		Level 2		Level 3
Money market funds	$	135,514	$	135,514	$	-	$	-
Certificates of deposit		127,123		-		127,123		-
Corporate debt securities		95,101		-		95,101		-
U.S. treasuries and government agency bonds		358,409		-		358,409		-
Auction-rate securities backed by student-loan notes		567		-		-		567
Mutual funds and money market funds under deferred compensation plan		54,836		54,836		-		-
Total	$	771,550	$	190,350	$	580,633	$	567