Loans Held for Investment and Allowance for Loan Losses - Schedule of Loans Modified and Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2021 USD ($) SecurityLoan	Mar. 31, 2020 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	5,000	7,000
Pre-Modification Recorded Investment	$ 846	$ 436
Post-Modification Recorded Investment	$ 846	$ 436
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	2,000	5,000
Pre-Modification Recorded Investment	$ 149	$ 288
Post-Modification Recorded Investment	$ 149	$ 288
Commercial [Member] \| Commercial – C&I [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	2,000
Pre-Modification Recorded Investment	$ 149
Post-Modification Recorded Investment	$ 149
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan		1,000
Pre-Modification Recorded Investment		$ 134
Post-Modification Recorded Investment		$ 134
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	3,000
Pre-Modification Recorded Investment	$ 697
Post-Modification Recorded Investment	$ 697
Real Estate [Member] \| Owner Occupied CRE [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	1,000
Pre-Modification Recorded Investment	$ 500
Post-Modification Recorded Investment	$ 500
Real Estate [Member] \| Residential [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	2,000
Pre-Modification Recorded Investment	$ 197
Post-Modification Recorded Investment	$ 197
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan		1,000
Pre-Modification Recorded Investment		$ 14
Post-Modification Recorded Investment		$ 14

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

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

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