Note 5 - Stockholders' Equity and Dilutive Equity Instruments (Details Textual) - $ / shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Out-of-the-money Warrants [Member]
Class of Warrant or Right, Outstanding (in shares)	5,923,399	5,923,399
Series A Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 57.06	$ 57.06
Series B Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	62.28	62.28
GLF Equity Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	$ 100.00	$ 100.00
In-the-money Warrants and Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares)	2,648,775	2,488,752