Note 3 - Fair Value Measurements - Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Warrant [Member]
Warrant liability	$ 30,496	$ 26,881
Fair Value, Inputs, Level 1 [Member] | Warrant [Member]
Warrant liability	0	0
Fair Value, Inputs, Level 2 [Member] | Warrant [Member]
Warrant liability	0	0
Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Warrant liability	30,496	26,881
Money Market Funds [Member]
Money market funds	17,596	52,905
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Money market funds	17,596	52,905
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Money market funds	0	0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Money market funds	$ 0	$ 0