Note 13 - Summary of Stock Options - Summary of Options Outstanding and Exercisable (Details)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Options outstanding, number (in shares) | shares	3,173,103
Options outstanding, weighted average exercise price (in dollars per share)	$ 7.51
Options outstanding, weighted average remaining contractual term (Year)	9 years
Options exercisable, number exercisable (in shares) | shares	774,800
Options exercisable, weighted average exercise price (in dollars per share)	$ 18.81
Range One [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	2,208,063
Options outstanding, weighted average exercise price (in dollars per share)	$ 2.73
Options outstanding, weighted average remaining contractual term (Year)	9 years 6 months
Options exercisable, number exercisable (in shares) | shares	259,301
Options exercisable, weighted average exercise price (in dollars per share)	$ 2.73
Range Two [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)	9 years 2 months 12 days
Options exercisable, number exercisable (in shares) | shares	0
Options exercisable, weighted average exercise price (in dollars per share)	$ 0
Range Three [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 10 months 24 days
Options exercisable, number exercisable (in shares) | shares	3,088
Options exercisable, weighted average exercise price (in dollars per share)	$ 4.71
Range Four [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 9 months 18 days
Options exercisable, number exercisable (in shares) | shares	62,219
Options exercisable, weighted average exercise price (in dollars per share)	$ 5.34
Range Five [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)	8 years 3 months 18 days
Options exercisable, number exercisable (in shares) | shares	2,364
Options exercisable, weighted average exercise price (in dollars per share)	$ 6.90
Range Six [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	830,825
Options outstanding, weighted average exercise price (in dollars per share)	$ 8.69
Options outstanding, weighted average remaining contractual term (Year)	7 years 10 months 24 days
Options exercisable, number exercisable (in shares) | shares	433,263
Options exercisable, weighted average exercise price (in dollars per share)	$ 8.69
Range Seven [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)	8 years 2 months 12 days
Options exercisable, number exercisable (in shares) | shares	11,271
Options exercisable, weighted average exercise price (in dollars per share)	$ 13.00
Range Eight [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	3,415
Options outstanding, weighted average exercise price (in dollars per share)	$ 2,873.63
Options outstanding, weighted average remaining contractual term (Year)	6 years 2 months 12 days
Options exercisable, number exercisable (in shares) | shares	3,294
Options exercisable, weighted average exercise price (in dollars per share)	$ 2,911.12