Note 9 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2016

Notes Tables

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

	Fair Value Measurement at March 31, 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	$	26,884	$	26,884	$	-	$	-
Certificates of deposit		18,607		-		18,607		-
U.S. treasuries and government agency bonds		155,086		-		155,086		-
Auction-rate securities backed by student-loan notes		5,353		-		-		5,353
Mutual funds under deferred compensation plan		9,505		9,505		-		-
Total	$	215,435	$	36,389	$	173,693	$	5,353

	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 loss included in other comprehensive income		(8	)
Balance at March 31, 2016	$	5,353

Schedule Of Level 3 Assumptions [Table Text Block]

	March 31, 2016			December 31, 2015
Time-to-liquidity (months)		24			24
Expected return		2.5%			2.9%
Discount rate	4.0%	-	7.0%	4.3%	-	7.3%