Note 8 - Share-based Compensation - Stock Option Activity (Details) - Share-Based Payment Arrangement, Option [Member]	3 Months Ended
	Mar. 31, 2022 $ / shares shares
Outstanding (in shares) | shares	624,531
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 2.13
Exercised (in shares) | shares	(129,933)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 1.98
Outstanding as of March 31, 2022 (in shares) | shares	494,598
Outstanding as of March 31, 2022 (in dollars per share) | $ / shares	$ 2.17
Stock options exercisable as of March 31, 2022 (in shares) | shares	494,598
Options exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 2.17