Note 11 - Stockholders' Equity - Assumptions for Fair Value of Warrants (Details)	Mar. 02, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Apr. 11, 2019 USD ($) shares	Mar. 20, 2019 USD ($) shares
Warrants in Connection with March 2019 Offering [Member]
Aggregate valuation on issuance date | $				$ 100,000
Number of warrants issued (in shares) | shares				84,000
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Exercise Price [Member]
Measurement Input				3.125
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Share Price [Member]
Measurement Input				2.08
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Risk Free Interest Rate [Member]
Measurement Input				0.0234
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Expected Term [Member]
Measurement Input				5.00
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Price Volatility [Member]
Measurement Input				0.80
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Expected Dividend Rate [Member]
Measurement Input				0
Warrants in Connection With the April 2019 Offering [Member]
Aggregate valuation on issuance date | $			$ 333,000
Number of warrants issued (in shares) | shares			636,364
Warrants in Connection With the April 2019 Offering [Member] | Measurement Input, Exercise Price [Member]
Measurement Input			1.375
Warrants in Connection With the April 2019 Offering [Member] | Measurement Input, Share Price [Member]
Measurement Input			0.89
Warrants in Connection With the April 2019 Offering [Member] | Measurement Input, Risk Free Interest Rate [Member]
Measurement Input			0.0231
Warrants in Connection With the April 2019 Offering [Member] | Measurement Input, Expected Term [Member]
Measurement Input			5.00
Warrants in Connection With the April 2019 Offering [Member] | Measurement Input, Price Volatility [Member]
Measurement Input			0.83
Warrants in Connection With the April 2019 Offering [Member] | Measurement Input, Expected Dividend Rate [Member]
Measurement Input			0
Warrants in Connection with the September 2019 Offering [Member]
Aggregate valuation on issuance date | $		$ 497,000
Number of warrants issued (in shares) | shares		2,115,738
Warrants in Connection with the September 2019 Offering [Member] | Measurement Input, Exercise Price [Member]
Measurement Input		0.375
Warrants in Connection with the September 2019 Offering [Member] | Measurement Input, Share Price [Member]
Measurement Input		0.36
Warrants in Connection with the September 2019 Offering [Member] | Measurement Input, Risk Free Interest Rate [Member]
Measurement Input		0.0155
Warrants in Connection with the September 2019 Offering [Member] | Measurement Input, Expected Term [Member]
Measurement Input		5.00
Warrants in Connection with the September 2019 Offering [Member] | Measurement Input, Price Volatility [Member]
Measurement Input		0.83
Warrants in Connection with the September 2019 Offering [Member] | Measurement Input, Expected Dividend Rate [Member]
Measurement Input		0
Warrants in Connection with March 2020 Offering [Member]
Aggregate valuation on issuance date | $	$ 453,000
Number of warrants issued (in shares) | shares	280,000
Warrants in Connection with March 2020 Offering [Member] | Measurement Input, Exercise Price [Member]
Measurement Input	3.125
Warrants in Connection with March 2020 Offering [Member] | Measurement Input, Share Price [Member]
Measurement Input	2.34
Warrants in Connection with March 2020 Offering [Member] | Measurement Input, Risk Free Interest Rate [Member]
Measurement Input	0.0088
Warrants in Connection with March 2020 Offering [Member] | Measurement Input, Expected Term [Member]
Measurement Input	4.99
Warrants in Connection with March 2020 Offering [Member] | Measurement Input, Price Volatility [Member]
Measurement Input	0.98
Warrants in Connection with March 2020 Offering [Member] | Measurement Input, Expected Dividend Rate [Member]
Measurement Input	0