Note 8 - Stockholders' Equity (Details Textual) - USD ($)			1 Months Ended	3 Months Ended
	May 08, 2020	Feb. 07, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Number of Shares Authorized to Issue (in shares)				185,000,000
Common Stock, Shares Authorized (in shares)				175,000,000		175,000,000
Common Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.18		$ 0.18
Preferred Stock, Shares Authorized (in shares)				10,000,000		10,000,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001		$ 0.001
Preferred Stock, Shares Issued, Total (in shares)				671		671
Proceeds from Warrant Exercises			$ 11,300,000	$ 0	$ 11,336,710
Class of Warrant or Right, Exercised During Period (in shares)					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)				0	1,677
Conversion of Stock, Shares Issued (in shares)					476,431
Convertible Preferred Stock, Shares Issued upon Conversion (in shares)			284		284
The 2018 Warrants [Member]
Class of Warrant or Right, Outstanding (in shares)				1,070,028
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)				$ 4.05
At The Market Offering [Member]
Common Stock, Par or Stated Value Per Share (in dollars per share)		$ 0.18
Stock to be Issued, Maximum Value		$ 5,000,000
At The Market Offering [Member] | Oppenheimer & Co. Inc. [Member]
Stock Issuance Costs, Commission Fee Percent		3.00%
At The Market Offering [Member] | Oppenheimer & Co. Inc. [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares)	68,098
Proceeds from Issuance of Common Stock	$ 150,253
Series A Junior Participating Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				750,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Preferred Stock, Shares Issued, Total (in shares)				0
Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				4,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Series B Convertible Preferred Stock [Member]
Preferred Stock, Shares Authorized (in shares)				25,000
Preferred Stock, Par or Stated Value Per Share (in dollars per share)				$ 0.001
Sale of Series A Convertible Preferred Stock [Member]
Preferred Stock, Shares Issued, Total (in shares)				0