Note 8 - Stockholders' Equity - Warrants (Details)	12 Months Ended
	Dec. 31, 2022 $ / shares shares
Balance, December 31, 2021 (in shares) | shares	2,424,724
Balance, December 31, 2021 (in dollars per share) | $ / shares	$ 6.36
Warrants for common stock sold (in shares) | shares	0
Warrants for common stock sold (in dollars per share) | $ / shares	$ 0
Warrants for common stock exercised (in shares) | shares	0
Warrants for common stock exercised (in dollars per share) | $ / shares	$ 0
Balance, December 31, 2022 (in shares) | shares	2,424,724
Balance, December 31, 2022 (in dollars per share) | $ / shares	$ 6.36