Note 9 - Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2016

Notes Tables

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

	Fair Value Measurement at June 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	$	27,864	$	27,864	$	-	$	-
Certificates of deposit		7,525		-		7,525		-
Corporate debt securities		7,581		-		7,581		-
U.S. treasuries and government agency bonds		146,712		-		146,712		-
Auction-rate securities backed by student-loan notes		5,294		-		-		5,294
Mutual funds under deferred compensation plan		10,162		10,162		-		-
Total	$	205,138	$	38,026	$	161,818	$	5,294

	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		(67	)
Balance at June 30, 2016	$	5,294

Schedule Of Level 3 Assumptions [Table Text Block]

	June 30,			December 31,
	2016			2015
Time-to-liquidity (months)		24			24
Expected return		2.1%			2.9%
Discount rate	4.2%	-	7.2%	4.3%	-	7.3%