Note 12 - Basic and Diluted Net Loss per Share - Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)	15,185,931	8,743,586
Share-Based Payment Arrangement, Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)	6,766,520	4,731,249
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)	1,120,300	1,323,995
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share (in shares)	7,299,111	2,688,342