Note 10 - Stock-based Compensation - Unvested Stock Activity (Details) - Restricted Stock [Member]	6 Months Ended
	Jun. 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	(45,744)
Vested, weighted average exercise price (in dollars per share) | $ / shares	$ 7.87
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	299,495
Unvested shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 7.10