Note 1 - Summary of Significant Accounting Policies - Option Activity (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($) $ / shares shares
Outstanding (in shares) | shares	362,640
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 3.96
Granted (in shares) | shares	3,000
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 5.76
Exercised (in shares) | shares	(1,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 3.70
Cancelled (in shares) | shares	(9,140)
Cancelled, weighted average exercise price (in dollars per share) | $ / shares	$ 3.41
Outstanding (in shares) | shares	355,500
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 3.99
Outstanding, weighted average remaining contractual term (Year)	7 years 3 months 18 days
Outstanding, aggregate intrinsic value | $	$ 1,422
Exercisable (in shares) | shares	194,100
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 3.71
Exercisable, weighted average remaining contractual term (Year)	6 years 9 months 7 days
Exercisable, aggregate intrinsic value | $	$ 827