Note 8 - Common Stock - Reserved Shares of Common Stock for Future Issuances (Details) - shares	Dec. 31, 2021	Dec. 31, 2020
Reserved shares of common stock for future issuances (in shares)	4,570,924	3,774,712
Equity-based Awards [Member]
Reserved shares of common stock for future issuances (in shares)	2,131,671	1,600,703
Share-based Payment Arrangement, Option [Member]
Reserved shares of common stock for future issuances (in shares)	2,439,253	2,173,776
Restricted Stock Units (RSUs) [Member]
Reserved shares of common stock for future issuances (in shares)	0	233