Note 9 - Stockholders' Equity - Summary of Warrant Activity (Details)	18 Months Ended
	Jun. 30, 2019 $ / shares shares
Outstanding, number of options (in shares) | shares	5,219,163
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 0.48
Expired, unexercised (in shares) | shares	(4,004,163)
Outstanding, number of options (in shares) | shares
Minimum [Member]
Expired, unexercised, weighted average exercise price (in dollars per share) | $ / shares	$ (0.51)
Outstanding, weighted average exercise price (in dollars per share) | $ / shares
Warrants with June 15, 2018 Expiration Date [Member]
Granted (in shares) | shares
Exercised (in shares) | shares	(1,215,000)
Warrants with June 15, 2018 Expiration Date [Member] | Minimum [Member]
Granted, weighted average exercise price (in dollars per share) | $ / shares
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ (0.50)