Note 8 - Warrants - Summary of Warrant Activity (Details)	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Outstanding, number of shares (in shares) | shares	79,100
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 4.75
Exercised, number of shares (in shares) | shares	(79,100)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 4.75
Outstanding, number of shares (in shares) | shares	0
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 0