Note 8 - Income Taxes (Details Textual) - USD ($)	9 Months Ended
Sep. 30, 2020	Dec. 31, 2019
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 3,000,000.0	$ 3,000,000.0
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	144,000	144,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	$ 0	$ 0
Domestic Tax Authority [Member]
Open Tax Year	2016 2017 2018 2019
State and Local Jurisdiction [Member]
Open Tax Year	2015 2016 2017 2018 2019

Tax year that remains open to examination under enacted tax laws, in CCYY format.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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- Definition

Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

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Amount of interest expense accrued for an underpayment of income taxes.

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- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (b)
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