Note 3 - Stock-based Compensation - Summary of Stock Options (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Shares outstanding (in shares) | shares	304,500
Shares outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 2.06
Shares outstanding, weighted average remaining contractual life (Year)	5 years
Shares outstanding, aggregate intrinsic value | $	$ 742,020
Shares vested and exercisable (in shares) | shares	256,500
Shares vested and exercisable, weighted average exercise price (in dollars per share) | $ / shares	$ 1.76
Shares vested and exercisable, weighted average remaining contractual life (Year)	4 years 73 days
Shares vested and exercisable, aggregate intrinsic value | $	$ 702,540