Note 12 - Summary of Stock Options - Summary of Options Outstanding and Exercisable (Details)	6 Months Ended
	Jun. 30, 2022 $ / shares shares
Options outstanding, number (in shares) | shares	4,124,009
Options outstanding, weighted average exercise price (in dollars per share)	$ 6.06
Options outstanding, weighted average remaining contractual term (Year)	8 years 9 months 18 days
Options exercisable, number exercisable (in shares) | shares	1,266,335
Options exercisable, weighted average exercise price (in dollars per share)	$ 13.10
Range One [Member]
Exercise price range, lower limit (in dollars per share)	0.71
Exercise price range, upper limit (in dollars per share)	$ 1.26
Options outstanding, number (in shares) | shares	955,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 1.25
Options outstanding, weighted average remaining contractual term (Year)	9 years 6 months
Options exercisable, number exercisable (in shares) | shares	98,024
Options exercisable, weighted average exercise price (in dollars per share)	$ 1.26
Range Two [Member]
Exercise price range, lower limit (in dollars per share)	2.28
Exercise price range, upper limit (in dollars per share)	$ 2.96
Options outstanding, number (in shares) | shares	2,207,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 2.73
Options outstanding, weighted average remaining contractual term (Year)	9 years
Options exercisable, number exercisable (in shares) | shares	544,316
Options exercisable, weighted average exercise price (in dollars per share)	$ 2.73
Range Three [Member]
Exercise price range, lower limit (in dollars per share)	3.06
Exercise price range, upper limit (in dollars per share)	$ 3.40
Options outstanding, number (in shares) | shares	10,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 3.20
Options outstanding, weighted average remaining contractual term (Year)	8 years 8 months 12 days
Options exercisable, number exercisable (in shares) | shares	3,146
Options exercisable, weighted average exercise price (in dollars per share)	$ 3.20
Range Four [Member]
Exercise price range, lower limit (in dollars per share)	4.45
Exercise price range, upper limit (in dollars per share)	$ 4.80
Options outstanding, number (in shares) | shares	11,900
Options outstanding, weighted average exercise price (in dollars per share)	$ 4.72
Options outstanding, weighted average remaining contractual term (Year)	8 years 4 months 24 days
Options exercisable, number exercisable (in shares) | shares	4,576
Options exercisable, weighted average exercise price (in dollars per share)	$ 4.71
Range Five [Member]
Exercise price range, lower limit (in dollars per share)	5.10
Exercise price range, upper limit (in dollars per share)	$ 5.40
Options outstanding, number (in shares) | shares	88,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 5.28
Options outstanding, weighted average remaining contractual term (Year)	8 years 3 months 18 days
Options exercisable, number exercisable (in shares) | shares	62,907
Options exercisable, weighted average exercise price (in dollars per share)	$ 5.34
Range Six [Member]
Exercise price range, lower limit (in dollars per share)	6.90
Exercise price range, upper limit (in dollars per share)	$ 6.90
Options outstanding, number (in shares) | shares	5,400
Options outstanding, weighted average exercise price (in dollars per share)	$ 6.90
Options outstanding, weighted average remaining contractual term (Year)	7 years 9 months 18 days
Options exercisable, number exercisable (in shares) | shares	3,038
Options exercisable, weighted average exercise price (in dollars per share)	$ 6.90
Range Seven [Member]
Exercise price range, lower limit (in dollars per share)	8.60
Exercise price range, upper limit (in dollars per share)	$ 8.91
Options outstanding, number (in shares) | shares	827,800
Options outstanding, weighted average exercise price (in dollars per share)	$ 8.69
Options outstanding, weighted average remaining contractual term (Year)	7 years 4 months 24 days
Options exercisable, number exercisable (in shares) | shares	533,718
Options exercisable, weighted average exercise price (in dollars per share)	$ 8.69
Range Eight [Member]
Exercise price range, lower limit (in dollars per share)	10.90
Exercise price range, upper limit (in dollars per share)	$ 13.60
Options outstanding, number (in shares) | shares	15,500
Options outstanding, weighted average exercise price (in dollars per share)	$ 12.64
Options outstanding, weighted average remaining contractual term (Year)	7 years 8 months 12 days
Options exercisable, number exercisable (in shares) | shares	13,209
Options exercisable, weighted average exercise price (in dollars per share)	$ 12.94
Range Nine [Member]
Exercise price range, lower limit (in dollars per share)	380.00
Exercise price range, upper limit (in dollars per share)	$ 9,920.00
Options outstanding, number (in shares) | shares	3,409
Options outstanding, weighted average exercise price (in dollars per share)	$ 2,878.01
Options outstanding, weighted average remaining contractual term (Year)	5 years 9 months 18 days
Options exercisable, number exercisable (in shares) | shares	3,401
Options exercisable, weighted average exercise price (in dollars per share)	$ 2,882.61