Note 9 - Fair Value of Assets and Liabilities - Valuation Techniques and Significant Unobservable Inputs for Level 3 Financial Assets (Details)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Warrant [Member]
Fair value	$ 1,075,000	$ 3,925,000	$ 3,279,000
Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Measurement Input, Discount for Lack of Marketability [Member] | Minimum [Member]
Input/range	0.25	0.21
Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Measurement Input, Discount for Lack of Marketability [Member] | Maximum [Member]
Input/range	0.46	0.44
Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Measurement Input, Price Volatility [Member] | Minimum [Member]
Input/range	0.65	0.55
Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Measurement Input, Price Volatility [Member] | Maximum [Member]
Input/range	1.22	1.2
Fair Value, Inputs, Level 3 [Member] | Warrant [Member]
Fair value	$ 1,075,000	$ 3,925,000