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Allowance for Loan Losses - Schedule of TDR (Detail)	12 Months Ended
	Dec. 31, 2020 Loan	Dec. 31, 2019 USD ($) Contract	Dec. 31, 2018 USD ($) Contract
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of loans modified | Contract		1	2
Pre- Modification Outstanding Recorded Investment		$ 382,000	$ 133,000
Post-Modification Outstanding Recorded Investment		$ 382,000	$ 133,000
Commercial and Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of loans modified | Loan	813
Commercial Real Estate Non Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of loans modified | Contract		1
Pre- Modification Outstanding Recorded Investment		$ 382,000
Post-Modification Outstanding Recorded Investment		$ 382,000
Residential Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of loans modified | Contract			1
Pre- Modification Outstanding Recorded Investment			$ 23,000
Post-Modification Outstanding Recorded Investment			$ 23,000
Farm Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Number of loans modified | Contract			1
Pre- Modification Outstanding Recorded Investment			$ 110,000
Post-Modification Outstanding Recorded Investment			$ 110,000

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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