Loans - Restructured in Troubled Debt (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) Loans	Dec. 31, 2016 USD ($) Loans
Financing Receivable, Modifications [Line Items]
Number of Loans \| Loans	19	15
Loan Balance	$ 17,303	$ 11,831
Specific Reserve	$ 5,689	$ 2,339
Commercial, Industrial, and Agricultural [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| Loans	10	7
Loan Balance	$ 5,213	$ 2,640
Specific Reserve	$ 245	$ 125
Commercial Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| Loans	9	8
Loan Balance	$ 12,090	$ 9,191
Specific Reserve	$ 5,444	$ 2,214
Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| Loans	0	0
Loan Balance	$ 0	$ 0
Specific Reserve	$ 0	$ 0
Consumer [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| Loans	0	0
Loan Balance	$ 0	$ 0
Specific Reserve	$ 0	$ 0
Credit Cards [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans \| Loans	0	0
Loan Balance	$ 0	$ 0
Specific Reserve	$ 0	$ 0

Financing receivable modifications specific reserve.

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- 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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Namespace Prefix:	us-gaap_
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- Definition

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

+ Details

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- Definition

The amount of the outstanding recorded investment related to 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 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554

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