Note 10 - Share-based Compensation - Summary of Non-vested RSUs (Details) - Restricted Stock Units (RSUs) [Member]	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Balance, shares (in shares) | shares	224,311
Balance, weighted average grant date fair value per share (in dollars per share) | $ / shares	$ 4.12
RSUs granted, shares (in shares) | shares	131,375
RSUs granted, weighted average grant date fair value per share (in dollars per share) | $ / shares	$ 3.61
RSUs released, shares (in shares) | shares	(118,472)
RSUs released, weighted average grant date fair value per share (in dollars per share) | $ / shares	$ 3.73
RSUs forfeited, shares (in shares) | shares	(36,943)
RSUs forfeited, weighted average grant date fair value per share (in dollars per share) | $ / shares	$ 3.49
Balance, shares (in shares) | shares	200,271
Balance, weighted average grant date fair value per share (in dollars per share) | $ / shares	$ 4.13