Note 4 - Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

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

	Carrying		Fair Value Measurement at December 31, 2022
	Value		Level 1		Level 2		Level 3
	(in thousands)
Cash and cash equivalents	$	13,331	$	13,331	$	—	$	—
Restricted cash	$	25	$	25	$	—	$	—
Marketable securities—held-to-maturity:
U.S. Government securities	$	5,956	$	5,956	$	—	$	—
Ownership interests	$	860	$	860	$	—	$	—

	Carrying		Fair Value Measurement at December 31, 2021
	Value		Level 1		Level 2		Level 3
	(In thousands)
Cash and cash equivalents	$	24,739	$	24,739	$	—	$	—
Restricted cash equivalents	$	25	$	25	$	—	$	—
Ownership interests	$	4,549	$	4,549	$	—	$	—