Note 12 - Stockholders' Equity - Assumptions for Fair Value of Warrants (Details)	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
Warrants in Connection with March 2019 Offering [Member] | Measurement Input, Price Volatility [Member]
Measurement Input			0.8
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
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
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