Note 9 - Stockholders' Equity - Outstanding Warrants (Details)	Dec. 31, 2020 $ / shares shares
Outstanding Warrants to Purchase Shares (in shares)	11,570,028
The 2018 Warrants [Member]
Outstanding Warrants to Purchase Shares (in shares)	1,070,028
Exercise Price (in dollars per share) | $ / shares	$ 4.05
Expiration date	May 30, 2022
The 2020 Warrants [Member]
Outstanding Warrants to Purchase Shares (in shares)	10,500,000
Exercise Price (in dollars per share) | $ / shares	$ 1
Expiration date	Jun. 21, 2025