Note 6 - Fair Value of Financial Instruments (Tables)

3 Months Ended

Mar. 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)	2018		Level 1		Level 2		Level 3
Assets:
Cash and cash equivalents	$	2,053	$	2,053	$	-	$	-
U.S. Treasury notes		13,514		13,514		-		-
Certificate of deposit		171		171		-		-
Total Assets	$	15,738	$	15,738	$	-	$	-

	Fair Value		Fair value measurement using
	December 31,
(in thousands)	2018		Level 1		Level 2		Level 3
Assets:
Cash and cash equivalents	$	5,234	$	5,234	$	-	$	-
U.S. Treasury notes		19,912		19,912		-		-
Certificate of deposit		171		171		-		-
Total Assets	$	25,317	$	25,317	$	-	$	-