Note 4 - Fair Value Measurement and Fair Value of Financial Instruments - Warrant Liabilities Inputs and Assumptions (Details)	Jun. 30, 2021	May 14, 2021	Sep. 30, 2020
Montage Warrant [Member] | Measurement Input, Price Volatility [Member]
Volatility	0.873		0.84
Montage Warrant [Member] | Measurement Input, Risk Free Interest Rate [Member]
Volatility	0.0070		0.0028
Montage Warrant [Member] | Measurement Input, Share Price [Member]
Volatility	4.30		1.86
Series C Warrants [Member] | Measurement Input, Price Volatility [Member]
Volatility	0.920		0.841
Series C Warrants [Member] | Measurement Input, Risk Free Interest Rate [Member]
Volatility	0.0050		0.0020
Series C Warrants [Member] | Measurement Input, Share Price [Member]
Volatility	4.30		1.86
Series D Warrants [Member] | Measurement Input, Price Volatility [Member]
Volatility	0.865	0.863
Series D Warrants [Member] | Measurement Input, Risk Free Interest Rate [Member]
Volatility	0.0090	0.0090
Series D Warrants [Member] | Measurement Input, Share Price [Member]
Volatility	4.30	2.50