Note 2 - Summary of Significant Accounting Policies - Potentially Dilutive Common Shares (Details) - shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Stock options to purchase common stock (Note 13) (in shares)	6,301,500	6,301,500
Total potentially dilutive common shares (in shares)	10,454,812	10,454,812
Series C Preferred Stock [Member]
Series C Convertible Preferred Stock and related accrued dividends (Note 9) (in shares)	524,736	524,736
Series D Preferred Stock [Member]
Series C Convertible Preferred Stock and related accrued dividends (Note 9) (in shares)	3,628,576	3,628,576