Note 8 - Stockholders' Equity (Details Textual) - USD ($)				1 Months Ended	3 Months Ended		9 Months Ended		15 Months Ended
	Sep. 25, 2020	Jul. 29, 2020	Feb. 07, 2020	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Dec. 31, 2019
Number of Shares Authorized to Issue (in shares)					185,000,000		185,000,000		185,000,000
Common Stock, Shares Authorized (in shares)					175,000,000		175,000,000		175,000,000	175,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.18		$ 0.18		$ 0.18	$ 0.18
Preferred Stock, Shares Authorized (in shares)					10,000,000		10,000,000		10,000,000	10,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001		$ 0.001		$ 0.001	$ 0.001
Preferred Stock, Shares Issued, Total (in shares)					623		623		623	671
Preferred Stock, Shares Outstanding, Ending Balance (in shares)					623		623		623	671
Proceeds from Issuance of Common Stock, Net							$ 4,686,298
Proceeds from Warrant Exercises				$ 11,300,000	$ 0		$ 0	$ 11,336,710
Class of Warrant or Right, Exercised During Period (in shares)						0		2,800,000
Stock Issued During Period, Shares, Warrant Exercised (in shares)								2,800,000
Conversion of Series B Convertible Preferred Stock into Common Stock [Member]
Conversion of Stock, Shares Converted (in shares)					3		48	1,708	5
Conversion of Stock, Shares Issued (in shares)					853	1,421	13,639	485,244
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)					284		284		284
The 2018 Warrants [Member]
Class of Warrant or Right, Outstanding (in shares)					1,070,028		1,070,028		1,070,028
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)					$ 4.05		$ 4.05		$ 4.05
At The Market Offering [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)	$ 0.18		$ 0.18
Stock to be Issued, Maximum Value			$ 5,000,000
At The Market Offering [Member] | Oppenheimer & Co. Inc. [Member]
Stock to be Issued, Maximum Value	$ 10,000,000
Stock Issuance Costs, Commission Fee Percent	3.00%		3.00%
Stock Issued During Period, Shares, New Issues (in shares)					1,083,531		1,243,639
Proceeds from Issuance of Common Stock, Net					$ 4,338,671		$ 4,686,298
Payments of Stock Issuance Costs					$ 135,157		$ 313,702
Proceeds from Issuance of Common Stock		$ 5,000,000
Series A Junior Participating Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)					750,000		750,000		750,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001		$ 0.001		$ 0.001
Preferred Stock, Shares Issued, Total (in shares)					0		0		0	0
Preferred Stock, Shares Outstanding, Ending Balance (in shares)					0		0		0	0
Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)					4,000		4,000		4,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001		$ 0.001		$ 0.001
Series B Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)					25,000		25,000		25,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)					$ 0.001		$ 0.001		$ 0.001
Sale of Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Issued, Total (in shares)					0		0		0	0
Preferred Stock, Shares Outstanding, Ending Balance (in shares)					0		0		0	0