Note 3 - Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2018

Notes Tables

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

	As of March 31, 2018
	Quoted Prices  in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets
Cash equivalents	$	16,481	$	-	$	-	$	16,481
Government securities		11,462		-		-		11,462
Total	$	27,943	$	-	$	-	$	27,943

	As of December 31, 2017
	Quoted Prices  in Active Markets (Level 1)		Significant Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total
Assets
Cash equivalents	$	11,662	$	-	$	-	$	11,662
Government securities		20,971		-		-		20,971
Total	$	32,633	$	-	$	-	$	32,633

Available-for-sale Securities [Table Text Block]

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
March 31, 2018
Government securities
(Due within 1 year)	$	11,475	$	-	$	(13	)	$	11,462
	$	11,475	$	-	$	(13	)	$	11,462
December 31, 2017
Government securities
(Due within 1 year)	$	20,991	$	-	$	(20	)	$	20,971
	$	20,991	$	-	$	(20	)	$	20,971