Note 6 - Fair Value Measurements (Details Textual) $ in Thousands	3 Months Ended
	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)
Asset Impairment Charges, Total	$ 0	$ 0
Fair Value, Inputs, Level 3 [Member] | Measurement Input, Share Price [Member]
Warrants and Rights Outstanding, Measurement Input	4.04
Fair Value, Inputs, Level 3 [Member] | Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input	2.42
Fair Value, Inputs, Level 3 [Member] | Measurement Input, Expected Term [Member]
Warrants and Rights Outstanding, Measurement Input	5.2
Fair Value, Inputs, Level 3 [Member] | Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input	82