Note 9 - Stockholders' Equity - Summary of Outstanding Options Under the Plan (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Outstanding (in shares)	63,327	56,661
Outstanding, weighted average exercise price (in dollars per share)	$ 2.594	$ 2.606
Granted (in shares)	13,332	13,332
Granted, weighted average exercise price (in dollars per share)	$ 5.60	$ 2.40
Exercised (in shares)	(7,806)	(266)
Exercised, weighted average exercise price (in dollars per share)	$ 2.35	$ 2.31
Expired (in shares)	(9,999)
Expired, weighted average exercise price (in dollars per share)	$ 2.55
Outstanding (in shares)	53,328	63,327
Outstanding, weighted average exercise price (in dollars per share)	$ 3.391	$ 2.594