Note 11 - Net Loss Per Share - Anti-dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Stock options to purchase common stock (in shares)	4,615,196	4,610,166
Share-Based Payment Arrangement, Option [Member]
Stock options to purchase common stock (in shares)	2,486,767	2,182,708
Restricted Stock Units (RSUs) [Member]
Stock options to purchase common stock (in shares)	0	2,734
Warrant [Member]
Stock options to purchase common stock (in shares)	2,128,429	2,424,724