Note 4 - Fair Value Measurements - Financial Instruments Measured at Fair Value on a Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Warrant [Member]
Warrant liability	$ 26,881
Fair Value, Inputs, Level 1 [Member] | Warrant [Member]
Warrant liability
Fair Value, Inputs, Level 2 [Member] | Warrant [Member]
Warrant liability
Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Warrant liability	26,881
Money Market Funds [Member]
Money market funds	52,905	$ 49,217
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Money market funds	52,905	49,217
Money Market Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Money market funds		0
Money Market Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Money market funds		$ 0