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Off Balance Sheet Activities - Outstanding Financial Instruments Whose Contract Amounts Represent Credit Risk (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Standby letters of credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Concentration of Risk	$ 791	$ 875
Commitments to extend credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Concentration of Risk	237,774	223,534
Credit card arrangements [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Concentration of Risk	$ 20,184	$ 18,316

X

- Definition

The fair value of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

+ Details

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Period Type:	instant

X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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