Note 3 - Warrants - Warrant Activity (Details) - Liability Classified Warrants [Member] - $ / shares	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Balance (in shares)	2,656,296
Balance, weighted average remaining contractual life (Year)	1 year 2 months 12 days	1 year 8 months 12 days
Expired warrants (in shares)	(26,914)
Balance (in shares)	2,629,382	2,656,296
Exercisable (in shares)	2,629,382
Exercisable, weighted average remaining contractual life (Year)	1 year 2 months 12 days
Minimum [Member]
Balance, warrant exercise price (in dollars per share)	$ 6.30
Expired warrants (in dollars per share)	13.92
Balance, warrant exercise price (in dollars per share)	6.30	$ 6.30
Exercisable, warrant exercise price (in dollars per share)	6.30
Maximum [Member]
Balance, warrant exercise price (in dollars per share)	16.80
Expired warrants (in dollars per share)	16.80
Balance, warrant exercise price (in dollars per share)	16.80	16.80
Exercisable, warrant exercise price (in dollars per share)	16.80
Weighted Average [Member]
Balance, warrant exercise price (in dollars per share)	9.49
Expired warrants (in dollars per share)	16.22
Balance, warrant exercise price (in dollars per share)	9.42	$ 9.49
Exercisable, warrant exercise price (in dollars per share)	$ 9.42