Note 12 - Stockholders' Equity - Summary of Warrant Activity (Details)	24 Months Ended
	Dec. 31, 2019 $ / shares shares
Outstanding, warrants (in shares) | shares	5,219,163
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 0.48
Granted, warrants (in shares) | shares
Granted, weighted average exercise price (in dollars per share) | $ / shares
Exercised, warrants (in shares) | shares	(1,215,000)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ (0.50)
Expired, unexercised, warrants (in shares) | shares	(4,004,163)
Expired, unexercised, weighted average exercise price (in dollars per share) | $ / shares	$ (0.51)
Outstanding, warrants (in shares) | shares
Outstanding, weighted average exercise price (in dollars per share) | $ / shares