Note 3 - Investments and Fair Value of Financial Instruments - Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Total assets measured at fair value	$ 32,702	$ 41,184
Total assets measured at fair value	(32,702)	(41,184)
Fair Value, Inputs, Level 1 [Member]
Total assets measured at fair value	32,702	41,184
Total assets measured at fair value	(32,702)	(41,184)
Fair Value, Inputs, Level 2 [Member]
Total assets measured at fair value	(0)	(0)
Total assets measured at fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Total assets measured at fair value	0	0
Total assets measured at fair value	0	0
Money Market Funds [Member]
Cash and Cash equivalents	32,702	41,184
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and Cash equivalents	32,702	41,184
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and Cash equivalents	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and Cash equivalents	$ 0	$ 0