Loans and Allowance for Loan Losses - Schedule of Loans Modified and Considered Troubled Debt Restructurings (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($) SecurityLoan	Mar. 31, 2017 USD ($) SecurityLoan
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	6	5
Pre-Modification Recorded Investment	$ 441	$ 290
Post-Modification Recorded Investment	$ 441	$ 290
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan		4
Pre-Modification Recorded Investment		$ 234
Post-Modification Recorded Investment		$ 234
Agriculture [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	1
Pre-Modification Recorded Investment	$ 4
Post-Modification Recorded Investment	$ 4
Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	2	1
Pre-Modification Recorded Investment	$ 363	$ 56
Post-Modification Recorded Investment	$ 363	$ 56
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number \| SecurityLoan	3
Pre-Modification Recorded Investment	$ 74
Post-Modification Recorded Investment	$ 74

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

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Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

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