Note 3 - Lincoln Park Financing (Details Textual) - USD ($)		3 Months Ended
	Mar. 31, 2020	Mar. 31, 2020	Mar. 31, 2019	Mar. 30, 2020
Proceeds from Issuance of Common Stock		$ 901,000
Lincoln Park Capital Fund, LLC [Member]
Stock Issued During Period, Shares, New Issues (in shares)		1,398,223	0
Proceeds from Issuance of Common Stock		$ 295,000
Stock Issued During Period, Shares, Additional Commitment (in shares)		14,420
Stock Purchase Agreement, Remaining Offering Costs	$ 122,000	$ 122,000
LPC Purchase Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)	1,785,715
Proceeds from Issuance of Common Stock	$ 250,000
Stock Purchase Agreement, Maximum Amount of Common Stock				$ 10,250,000
Stock Issued During Period, Shares, Commitment Fee (in shares)		2,928,571
Stock Issued During Period, Value, Commitment Fee		$ 527,000