Note 11 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2024

Notes Tables

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

	September 30, 2024
	Total		Level 1		Level 2		Level 3
Money market funds	$	282,883	$	282,883	$	-	$	-
Certificates of deposit		171,065		-		171,065		-
Corporate debt securities		14,236		-		14,236		-
U.S. treasuries and government agency bonds		581,156		-		581,156		-
Auction-rate securities backed by student-loan notes		173		-		-		173
Mutual funds and money market funds under deferred compensation plan		61,637		61,637		-		-
Total	$	1,111,150	$	344,520	$	766,457	$	173

	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