Note 9 - Warrants - Warrants (Details)	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Number of Warrants Outstanding (in shares) | shares	46,461,630
Warrant One [Member]
Exercise Prices (in dollars per share) | $ / shares	$ 0.37
Number of Warrants Outstanding (in shares) | shares	530,381
Range of Expiration Dates	May 2022
Warrant Two [Member]
Exercise Prices (in dollars per share) | $ / shares	$ 0.68
Number of Warrants Outstanding (in shares) | shares	45,823,528
Range of Expiration Dates	March 2021 - March 2025
Warrant Three [Member]
Number of Warrants Outstanding (in shares) | shares	107,721
Range of Expiration Dates	September 2021 - September 2027
Warrant Three [Member] | Minimum [Member]
Exercise Prices (in dollars per share) | $ / shares	$ 13.00
Warrant Three [Member] | Maximum [Member]
Exercise Prices (in dollars per share) | $ / shares	$ 52.20