Note 9 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2016

Notes Tables

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

	Fair Value Measurement at September 30, 2016
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		Level 1		Level 2		Level 3
Money market funds	$	47,261	$	47,261	$	-	$	-
Certificates of deposit		7,495		-		7,495		-
Corporate debt securities		20,665		-		20,665		-
U.S. treasuries and government agency bonds		121,424		-		121,424		-
Auction-rate securities backed by student-loan notes		5,382		-		-		5,382
Mutual funds under deferred compensation plan		9,304		9,304		-		-
Total	$	211,531	$	56,565	$	149,584	$	5,382

	Fair Value Measurement at December 31, 2015
			Quoted Prices in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
	Total		Level 1		Level 2		Level 3
Money market funds	$	31,640	$	31,640	$	-	$	-
Certificates of deposit		21,574		-		21,574		-
U.S. treasuries and government agency bonds		123,532		-		123,532		-
Auction-rate securities backed by student-loan notes		5,361		-		-		5,361
Mutual funds under deferred compensation plan		8,279		8,279		-		-
Total	$	190,386	$	39,919	$	145,106	$	5,361

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

Balance at January 1, 2016	$	5,361
Change in unrealized gain included in other comprehensive income		21
Balance at September 30, 2016	$	5,382

Schedule Of Level 3 Assumptions [Table Text Block]

	September 30,			December 31,
	2016			2015
Time-to-liquidity (months)		24			24
Expected return		2.5%			2.9%
Discount rate	3.7%	-	6.7%	4.3%	-	7.3%