Note 10 - Stockholders' Equity - Fair Value Measurement of Warrant Liability (Details) (Parentheticals) - $ / shares	Dec. 31, 2020	May 21, 2020	Dec. 31, 2019
Warrants (in shares)	515,000		0
Warrants, exercise price (in dollars per share)		$ 5.00

Exercise price per share or per unit of warrants or rights outstanding.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant