Note 10 - Stock-based Compensation Plan - Unvested Stock Activity (Details) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Unvested shares outstanding (in shares) | shares	237,155
Unvested shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 4.93
Granted, number of shares (in shares) | shares	81,468
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 10.62
Vested, number of shares (in shares) | shares	(22,200)
Vested, weighted average exercise price (in dollars per share) | $ / shares	$ 8.56
Forfeited, number of shares (in shares) | shares
Forfeited, weighted average exercise price (in dollars per share) | $ / shares
Unvested shares outstanding (in shares) | shares	296,423
Unvested shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 6.22