Loans Held for Investment and Allowance for Credit Losses - Schedule of Loans Modified and Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2020 USD ($) SecurityLoan	Mar. 31, 2019 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	7	13
Pre-Modification Recorded Investment	$ 436	$ 1,173
Post-Modification Recorded Investment	$ 436	$ 1,173
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	5	1
Pre-Modification Recorded Investment	$ 288	$ 157
Post-Modification Recorded Investment	$ 288	$ 157
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	1	8
Pre-Modification Recorded Investment	$ 134	$ 367
Post-Modification Recorded Investment	$ 134	$ 367
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan		4
Pre-Modification Recorded Investment		$ 649
Post-Modification Recorded Investment		$ 649
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	1
Pre-Modification Recorded Investment	$ 14
Post-Modification Recorded Investment	$ 14

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No definition available.

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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=118936363&loc=SL6953676-111524

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

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- Definition

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

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