Note 6 - Shareholders' Equity (Details Textual) - USD ($)		3 Months Ended
	Aug. 13, 2020	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period (in shares)		(0)
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price (in dollars per share)		$ 0
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.001	$ 0.001		$ 0.001
Open Market Sale Agreement [Member]
Sale of Stock, Authorized Offering Amount	$ 50,000,000.0
Sale of Stock, Percentage of Commissions Paid of Gross Proceeds From Sale Of Each Share	3.00%
Sale of Stock, Reimbursable Legal Expenses	$ 50,000
Sale of Stock, Termination Amount Under Agreement	$ 50,000,000.0
Common Stock [Member]
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures (in shares)		247,961
Share-based Compensation Arrangements by Share-based Payment Award, Other than Options, Grants in Period, Weighted Average Exercise Price (in dollars per share)		$ 1.38
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period (in shares)			35,000
Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price (in dollars per share)			$ 1.21