Note 6 - Stockholders' Equity - Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Outstanding, number of units, balance (in shares)	1,206,709	1,166,709
Outstanding, weighted average exercise price, beginning balance (in dollars per share)	$ 13.96	$ 17.93	$ 18.54
Outstanding, weighted average remaining contractual term (Year)	7 years 80 days	6 years 354 days	7 years 306 days
Outstanding, aggregate intrinsic value	$ 91,475		$ 90,097
Granted, number of units (in shares)	714,350	85,000
Granted, weighted average exercise price (in dollars per share)	$ 5.76	$ 3.46
Cancelled, number of units (in shares)	(254,262)	(45,000)
Cancelled, weighted average exercise price (in dollars per share)	$ 9.78	$ 6.55
Outstanding, number of units, balance (in shares)	1,666,797	1,206,709	1,166,709
Exercisable, number of units (in shares)	928,780
Exercisable, weighted average exercise price (in dollars per share)	$ 20.59
Exercisable, weighted average remaining contractual term (Year)	5 years 266 days
Exercisable, aggregate intrinsic value	$ 30,491