Note 3 - Stock-based Compensation - Stock Option Activity (Details)	3 Months Ended
	Mar. 31, 2020 $ / shares shares
Outstanding (in shares) | shares	14,500
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 8.78
Exercised (in shares) | shares	(1,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 8.78
Outstanding (in shares) | shares	13,500
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 8.78
Exercisable (in shares) | shares	13,500
Exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 8.78