Note 9 - Stockholders' Equity - Fair Value of Liability Warrants (Details) - Warrant [Member]	Dec. 31, 2020 $ / shares yr
Measurement Input, Share Price [Member] | The 2020 Warrants at End-of-year Valuation [Member]
Liability warrants, measurement input (in dollars per share)	0.95
Measurement Input, Share Price [Member] | Minimum [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)	0.87
Measurement Input, Share Price [Member] | Maximum [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)	0.89
Measurement Input, Exercise Price [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)	1
Measurement Input, Exercise Price [Member] | The 2020 Warrants at End-of-year Valuation [Member]
Liability warrants, measurement input (in dollars per share)	1
Measurement Input, Risk Free Interest Rate [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)	0.0028
Measurement Input, Risk Free Interest Rate [Member] | The 2020 Warrants at End-of-year Valuation [Member]
Liability warrants, measurement input (in dollars per share)	0.0027
Measurement Input, Expected Term [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share) | yr	4
Measurement Input, Expected Term [Member] | The 2020 Warrants at End-of-year Valuation [Member]
Liability warrants, measurement input (in dollars per share) | yr	4
Measurement Input, Expected Dividend Rate [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)
Measurement Input, Expected Dividend Rate [Member] | The 2020 Warrants at End-of-year Valuation [Member]
Liability warrants, measurement input (in dollars per share)
Measurement Input, Price Volatility [Member] | The 2020 Warrants at End-of-year Valuation [Member]
Liability warrants, measurement input (in dollars per share)	1.27
Measurement Input, Price Volatility [Member] | Minimum [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)	1.07
Measurement Input, Price Volatility [Member] | Maximum [Member] | The 2020 Warrants at Initial Valuation [Member]
Liability warrants, measurement input (in dollars per share)	1.24