Note 7 - Stockholders' Equity (Details Textual) - USD ($)			1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 27, 2020	Dec. 13, 2019	Nov. 12, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	May 19, 2020
Proceeds from Issuance of Common Stock, Net						$ 5,580,000	$ 756,000
Share-based Payment Arrangement, Expense				$ 234,000	$ 253,000	$ 615,000	$ 459,000
Registered Direct Offering [Member]
Stock Issued During Period, Shares, New Issues (in shares)	1,000,002
Shares Issued, Price Per Share (in dollars per share)	$ 3.50
Proceeds from Issuance of Common Stock	$ 3,500,000
Payments of Stock Issuance Costs	$ 393,000
At The Market Offering Agreement [Member]
Stock Issued During Period, Shares, New Issues (in shares)						517,740
Proceeds from Issuance of Common Stock						$ 2,785,000
Payments of Stock Issuance Costs						$ 312,000
Maximum Offering Price for Issuance of Common Stock		$ 4,400,000						$ 15,280,313
Commission as Percentage of Gross Proceeds		3.00%
Shares Issued, Average Price Per Share (in dollars per share)						$ 5.38
Proceeds from Issuance of Common Stock, Net						$ 2,473,000
At The Market Offering Agreement [Member] | Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares)			964,130
Proceeds from Issuance of Common Stock			$ 2,771,000
Payments of Stock Issuance Costs			$ 88,000
Shares Issued, Average Price Per Share (in dollars per share)			$ 2.87
Proceeds from Issuance of Common Stock, Net			$ 2,683,000