Note 12 - Stock-based Compensation - Number of Stock Option Awards Exercisable and their Weighted Average Exercise Price (Details)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Upper Exercise Price Range (in dollars per share)	$ 18
Outstanding Number (in shares) | shares	33,093
Outstanding Weighted Average Remaining Life (Year)	7 years 6 months
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 7.68
Exercisable Number (in shares) | shares	15,561
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 6.34
Exercise Price Range 01 [Member]
Upper Exercise Price Range (in dollars per share)	$ 3
Outstanding Number (in shares) | shares	1,874
Outstanding Weighted Average Remaining Life (Year)	5 years 10 months 24 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 2.30
Exercisable Number (in shares) | shares	1,158
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 2.12
Exercise Price Range 02 [Member]
Upper Exercise Price Range (in dollars per share)	$ 6
Outstanding Number (in shares) | shares	10,190
Outstanding Weighted Average Remaining Life (Year)	6 years 6 months
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 4.22
Exercisable Number (in shares) | shares	7,317
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 4.41
Exercise Price Range 03 [Member]
Upper Exercise Price Range (in dollars per share)	$ 9
Outstanding Number (in shares) | shares	10,599
Outstanding Weighted Average Remaining Life (Year)	8 years 2 months 12 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 7.89
Exercisable Number (in shares) | shares	4,317
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 7.56
Exercise Price Range 04 [Member]
Upper Exercise Price Range (in dollars per share)	$ 12
Outstanding Number (in shares) | shares	8,228
Outstanding Weighted Average Remaining Life (Year)	8 years 1 month 6 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 11.14
Exercisable Number (in shares) | shares	2,120
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 10.86
Exercise Price Range 05 [Member]
Upper Exercise Price Range (in dollars per share)	$ 15
Outstanding Number (in shares) | shares	1,291
Outstanding Weighted Average Remaining Life (Year)	6 years 9 months 18 days
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 13.10
Exercisable Number (in shares) | shares	535
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 12.31
Exercise Price Range 06 [Member]
Upper Exercise Price Range (in dollars per share)	$ 18
Outstanding Number (in shares) | shares	911
Outstanding Weighted Average Remaining Life (Year)	9 years
Outstanding Weighted Average Exercise Price (in dollars per share)	$ 15.95
Exercisable Number (in shares) | shares	114
Exercisable Weighted Average Exercise Price (in dollars per share)	$ 15.56