Note 9 - Stockholders' Equity - Warrants (Details) - shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Balance, Warrants (in shares)	4,490,104	126,875
Warrants issued in connection with public offering and private placement (in shares)	0	4,363,229
Exercises and conversions (in shares)	0	0
Balance, Warrants (in shares)	4,490,104	4,490,104