Note 3 - Fair Value of Financial Instruments - Financial Assets Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Money Market Funds [Member]
Money market funds, Fair Value	$ 38,000	$ 31,403
Fair Value, Recurring [Member]
Total assets	57,308	36,361
Fair Value, Recurring [Member] | US Treasury Securities [Member]
Investments, Fair Value Disclosure	19,308	4,958
Fair Value, Recurring [Member] | Money Market Funds [Member]
Money market funds, Fair Value	38,000	31,403
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total assets	38,000	31,403
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Investments, Fair Value Disclosure	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
Money market funds, Fair Value	38,000	31,403
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total assets	19,308	4,958
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Investments, Fair Value Disclosure	19,308	4,958
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
Money market funds, Fair Value	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total assets	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Investments, Fair Value Disclosure	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
Money market funds, Fair Value	$ 0	$ 0