Note 7 - Series A Preferred Financing (Details Textual) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	Jan. 09, 2020	Aug. 02, 2017	Dec. 31, 2019	Dec. 31, 2018
Preferred Stock, Par or Stated Value Per Share			$ 0.001	$ 0.001
Preferred Stock, Shares Authorized			10,000,000	10,000,000
Conversion of Series A Preferred Stock to Common Stock [Member] | Subsequent Event [Member]
Conversion of Stock, Shares Issued	476,276
Conversion of Stock, Shares Converted	18,954
Series A Convertible Preferred Stock [Member]
Stock Issued During Period, Shares, New Issues		22,000
Preferred Stock, Par or Stated Value Per Share		$ 0.001	$ 0.001	$ 0.001
Shares Issued, Price Per Share		$ 1,000
Proceeds from Issuance of Convertible Preferred Stock		$ 22.0
Payments of Stock Issuance Costs		$ 0.5
Convertible Preferred Stock, Shares Issued upon Conversion		25
Convertible Preferred Stock, Conversion Price of Shares Issued upon Conversion		$ 39.80
Convertible Preferred Stock, Maximum Ownership Percentage Allowed after Conversion of Stock		9.985%
Preferred Stock, Shares Authorized			22,000	22,000
Conversion of Stock, Shares Issued			76,540
Preferred Stock, Shares Issued, Total			18,954	22,000
Preferred Stock, Liquidation Preference Per Share			$ 0.001
Preferred Stock, Shares Outstanding, Ending Balance			18,954	22,000