Note 5 - Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

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

			Fair Value Measurements at Reporting Date Using
			Quoted Prices in
			Active Markets		Significant Other		Significant
			for Identical Assets		Observable Inputs		Unobservable Inputs
	September 30, 2019		(Level 1)		(Level 2)		(Level 3)		Amortized Cost
Cash equivalents:
Money market funds	$	6,406	$	6,406	$	-	$	-	$	6,406
Investments:
U.S. treasury bills	$	69,825	$	69,825	$	-	$	-	$	69,821

			Fair Value Measurements at Reporting Date Using
			Quoted Prices in
			Active Markets		Significant Other		Significant
			for Identical Assets		Observable Inputs		Unobservable Inputs
	December 31, 2018		(Level 1)		(Level 2)		(Level 3)		Amortized Cost
Cash equivalents:
Money market funds	$	4,984	$	4,984	$	-	$	-	$	4,984
Investments:
U.S. treasury bills	$	69,972	$	69,972	$	-	$	-	$	69,972