Note 3 - Warrants (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Share-Based Payment Arrangement, Expense	$ 499,000	$ 527,000
Equity Classified Warrants [Member]
Class of Warrant or Right, Outstanding (in shares)	646,501		646,501
Class of Warrant or Right, Vested and Exercisable (in shares)	404,434		400,859
Share-Based Payment Arrangement, Expense	$ 46,000	$ 83,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount	$ 391,000