Note 7 - Financial Instruments (Details Textual) $ / shares in Units, shares in Millions	Sep. 30, 2021 USD ($) shares	Dec. 31, 2020 USD ($)	Sep. 02, 2016 USD ($) $ / shares shares
Warrants and Rights Outstanding \| $	$ 6,344,663	$ 6,639,211
The 2016 Warrant [Member]
Class of Warrant or Right Outstanding, Common Stock Value Used to Determine Number of Shares Called \| $			$ 4,000,000.0
Class of Warrant or Right Outstanding, Common Stock Price Per Share Used to Determine Number of Shares Called (in dollars per share) \| $ / shares			$ 2.29
Warrants and Rights Outstanding, Term (Year)			10 years
Class of Warrant or Right, Subscription Price of Warrants or Rights (in dollars per share) \| $ / shares			$ 1.50
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) \| $ / shares			$ 1.50
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares) \| shares	1.0		2.7
Warrants and Rights Outstanding \| $	$ 6,300,000
Warrants and Rights Outstanding, Measurement Input	6,600,000
The 2016 Warrant [Member] \| Measurement Input, Risk Free Interest Rate [Member]
Warrants and Rights Outstanding, Measurement Input	0.0096	0.0046
The 2016 Warrant [Member] \| Measurement Input, Expected Dividend Rate [Member]
Warrants and Rights Outstanding, Measurement Input	0	0
The 2016 Warrant [Member] \| Measurement Input, Expected Term [Member]
Warrants and Rights Outstanding, Measurement Input	4.9	5.7
The 2016 Warrant [Member] \| Measurement Input, Price Volatility [Member]
Warrants and Rights Outstanding, Measurement Input	0.50	0.80

The price per share of common stock to be used in determining the number of shares called by each warrant or right.

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- Definition

The value of common stock to be used in determining the number of shares called by each warrant or right.

+ References

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- Definition

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

+ References

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- Definition

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

+ References

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=123467817&loc=d3e21475-112644

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- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

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- Definition

Value of outstanding derivative securities that permit the holder the right to purchase securities (usually equity) from the issuer at a specified price.

+ References

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- Definition

Value of input used to measure outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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- Definition

Period between issuance and expiration of outstanding warrant and right embodying unconditional obligation requiring redemption by transferring asset at specified or determinable date or upon event certain to occur, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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