Note 9 - Warrants - Summary of Warrant Activity (Details) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Beginning balance (in shares)	0	79,100
Beginning balance (in dollars per share)	$ 0	$ 4.75
Exercised, number of shares (in shares)	0	(79,100)
Exercised, weighted average exercise price (in dollars per share)	$ 0	$ 4.75
Ending balance (in shares)	0	0
Ending balance (in dollars per share)	$ 0	$ 0