Note 9 - Stock-based Compensation Expense - Restricted Stock and Restricted Stock Units Activity (Details)	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Restricted Stock [Member]
Unvested outstanding at beginning of period (in shares) | shares	0
Unvested outstanding at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0
Granted (in shares) | shares	42,800
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.65
Vested (in shares) | shares	0
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0
Forfeited/Cancelled (in shares) | shares	(4,746)
Forfeited/Cancelled, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.65
Unvested outstanding at end of period (in shares) | shares	38,054
Unvested outstanding at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.65
Restricted Stock Units (RSUs) [Member]
Unvested outstanding at beginning of period (in shares) | shares	8,750
Unvested outstanding at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 5.00
Granted (in shares) | shares	2,333
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 5.36
Vested (in shares) | shares	(5,583)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 5.32
Unvested outstanding at end of period (in shares) | shares	5,500
Unvested outstanding at beginning of period, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.83