Note 1 - Summary of Significant Accounting Policies - Stock Option Activity (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) $ / shares shares
Outstanding (in shares) | shares	372,200
Outstanding, weighted average exercise price per share (in dollars per share) | $ / shares	$ 3.85
Granted (in shares) | shares	11,300
Granted, weighted average exercise price per share (in dollars per share) | $ / shares	$ 2.95
Cancelled (in shares) | shares	(16,667)
Cancelled, weighted average exercise price per share (in dollars per share) | $ / shares	$ 3.65
Outstanding (in shares) | shares	366,833
Outstanding, weighted average exercise price per share (in dollars per share) | $ / shares	$ 3.83
Outstanding, weighted average remaining contractual term (Year)	7 years 321 days
Outstanding, aggregate intrinsic value | $	$ 317
Exercisable (in shares) | shares	181,640
Exercisable, weighted average exercise price per share (in dollars per share) | $ / shares	$ 3.72
Exercisable, weighted average remaining contractual term (Year)	7 years 160 days
Exercisable, aggregate intrinsic value | $	$ 176