Note 9 - Stockholders' Equity - Shares of Common Stock Reserved for Issuance (Details) - shares	Mar. 31, 2023	Dec. 31, 2022
Common stock reserved for issuance (in shares)	29,582,129	29,635,697
Common Warrants [Member]
Common stock reserved for issuance (in shares)	227,434	227,434
Share-Based Payment Arrangement, Option [Member]
Common stock reserved for issuance (in shares)	19,305,219	14,725,261
Restricted Stock Units (RSUs) [Member]
Common stock reserved for issuance (in shares)	3,708,708	808,310
Future Grants of Equity Awards [Member]
Common stock reserved for issuance (in shares)	4,540,768	12,074,692
ESPP [Member]
Common stock reserved for issuance (in shares)	1,800,000	1,800,000