Note 9 - Stock-based Compensation Plan - Unvested Stock Activity (Details) - Restricted Stock [Member]	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Unvested shares outstanding (in shares) | shares	165,031
Unvested shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 6.55
Granted, number of shares (in shares) | shares	74,000
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 3.59
Vested, number of shares (in shares) | shares	(61,636)
Vested, weighted average exercise price (in dollars per share) | $ / shares	$ 4.90
Forfeited, number of shares (in shares) | shares	(15,065)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 5.02
Unvested shares outstanding (in shares) | shares	162,330
Unvested shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 5.61