Note 8 - Stock-based Compensation - Restricted Stock Activity (Details) - Restricted Stock Units (RSUs) [Member]	3 Months Ended
	Mar. 31, 2022 $ / shares shares
Beginning balance, unvested restricted stock units, shares (in shares) | shares	45,003
Beginning balance, unvested restricted stock units, weighted average grant date fair value (in dollars per share) | $ / shares	$ 1.51
Forfeited, restricted stock units, shares (in shares) | shares	0
Forfeited, restricted stock units, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0
Vested, restricted stock units, shares (in shares) | shares	(45,003)
Vested, restricted stock units, weighted average grant date fair value (in dollars per share) | $ / shares	$ 1.51
Ending balance, unvested restricted stock units, shares (in shares) | shares	0
Ending balance, unvested restricted stock units, weighted average grant date fair value (in dollars per share) | $ / shares	$ 0