Loans - Summary of Troubled Debt Restructuring (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) Contract	Dec. 31, 2016 USD ($) Contract
Financing Receivable, Modifications [Line Items]
Number of loans restructured \| Contract	8	5
Pre-Modification Recorded Investment	$ 490	$ 3,708
Post-Modification Recorded Investment	$ 490	$ 3,708
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of loans restructured \| Contract	2	4
Pre-Modification Recorded Investment	$ 150	$ 3,607
Post-Modification Recorded Investment	$ 150	$ 3,607
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of loans restructured \| Contract	4
Pre-Modification Recorded Investment	$ 288
Post-Modification Recorded Investment	$ 288
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of loans restructured \| Contract	2	1
Pre-Modification Recorded Investment	$ 52	$ 101
Post-Modification Recorded Investment	$ 52	$ 101

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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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