Note 9 - Fair Value Measurement (Details Textual) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Gain (Loss) on Sale of Assets and Asset Impairment Charges	$ (0)	$ (118,000)	$ (118,000)

Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Name:	us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration