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Note 3 - Loans and Allowance for Loan Losses - Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019
Number of loans	0	3	0
Pre-modification	$ 0	$ 1,733
Post-modification	$ 0	$ 1,733
Financial Asset, 30 Days Past Due or More [Member]
Number of loans	3	3
Recorded investment	$ 1,733	$ 1,733
Agricultural [Member]
Number of loans	0	1
Pre-modification	$ 0	$ 67
Post-modification	$ 0	$ 67
Agricultural [Member] | Financial Asset, 30 Days Past Due or More [Member]
Number of loans	1	1
Recorded investment	$ 67	$ 67
Commercial Real Estate Portfolio Segment [Member]
Number of loans	0	2
Pre-modification	$ 0	$ 1,666
Post-modification	$ 0	$ 1,666
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 Days Past Due or More [Member]
Number of loans	2	2
Recorded investment	$ 1,666	$ 1,666

X

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

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-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

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