Note 10 - Stockholders' Equity - Summary of Warrants (Details) - $ / shares	Sep. 30, 2020	Sep. 29, 2020	Sep. 24, 2020	Jun. 26, 2020
Number of warrants (in shares)	3,850,337
Weighted Average [Member]
Exercise price (in dollars per share)	$ 4.53
Series I Warrants [Member]
Number of warrants (in shares)	62,626
Exercise price (in dollars per share)	$ 5
June 2020 Warrants [Member]
Number of warrants (in shares)	120,000
Exercise price (in dollars per share)	$ 5	$ 5		$ 10
Weighted-Average Remaining Life (excluding Pre-Funded Warrants)(in years) (Year)				5 years
Pre-Funded Warrants [Member]
Number of warrants (in shares)	376,042
Exercise price (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Unit, Conversion and Management Warrants [Member]
Number of warrants (in shares)	3,163,669
Exercise price (in dollars per share)	$ 5
Representative Warrants [Member]
Number of warrants (in shares)	128,000
Exercise price (in dollars per share)	$ 5.5		$ 5.50
Weighted-Average Remaining Life (excluding Pre-Funded Warrants)(in years) (Year)			3 years
Outstanding Warrants Excluding Pre-Funded Warrants [Member] | Weighted Average [Member]
Weighted-Average Remaining Life (excluding Pre-Funded Warrants)(in years) (Year)	4 years 328 days