Note 5 - Fair Value of Financial Instruments (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2020

Dec. 31, 2019

Notes Tables

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

	Fair Value		Fair value measurement using
	March 31,
(in thousands)	2020		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	15,596	$	15,596		-		-
Total Assets	$	15,596	$	15,596	$	-	$	-

	Fair Value		Fair value measurement using
	December 31,
(in thousands)	2019		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	1,819	$	1,819	$	-	$	-
U.S. Treasury notes		18,230		18,230		-		-
Total Assets	$	20,049	$	20,049	$	-	$	-

	Fair Value		Fair value measurement using
	December 31,
(in thousands)	2019		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	1,819	$	1,819	$	-	$	-
U.S. Treasury notes		18,230		18,230		-		-
Total Assets	$	20,049	$	20,049	$	-	$	-

	Fair Value		Fair value measurement using
	December 31,
(in thousands)	2018		Level 1		Level 2		Level 3
Cash equivalents:
Money market funds	$	103	$	103	$	-	$	-
U.S. Treasury notes		6,018		6,018
Available-for-sale marketable securities:
U.S. Treasury notes		13,959		13,959		-		-
Total Assets	$	20,080	$	20,080	$	-	$	-