Note 10 - Stock-based Compensation - Unvested Stock Activity (Details) - Restricted Stock [Member]	9 Months Ended
	Sep. 30, 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	126,209
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 11.74
Vested, number of shares (in shares) | shares	(78,206)
Vested, weighted average exercise price (in dollars per share) | $ / shares	$ 7.24
Forfeited, number of shares (in shares) | shares	(18,125)
Forfeited, weighted average exercise price (in dollars per share) | $ / shares	$ 9.02
Unvested shares outstanding (in shares) | shares	267,033
Unvested shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 7.19