Fair Value - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	$ 587,602	$ 516,844
Investment securities held by the company	587,602	516,844
Loan held for sale, at fair value	16,641	21,485
Contractual principal balance of Loan held for sale	16,413	21,225
Difference in amount of loan held for sale	228	260
Impaired loans, carrying amount	8,274	9,729
Valuation allowance for loans losses	5,411	4,911
Provision for Loan Losses	2,230	4,226
Other real estate, carrying value	150	250
Cost of Real Estate Sales	100	150
Interest Income Securities Measured At Fair Value	1
Servicing Asset at Fair Value, Other Changes in Fair Value	155
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	12,500
Fair Value, Measurements, Recurring [Member] \| Obligations of State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	76,485	64,799
Fair Value, Measurements, Recurring [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	733	684
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	12,522	5,433
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Obligations of State and Political Subdivisions [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	12,169	4,075
Fair Value, Measurements, Recurring [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Equity Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Securities	$ 353	$ 353
Maximum [Member] \| Short-term Borrowings [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Maturity duration of short-term borrowing		90 days

Contractual Amounts of Financial Instrument

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- Definition

Debt Instruments, Maturity Duration

+ References

No definition available.

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- Definition

Interest income on securities measured at fair value through earnings.

+ References

No definition available.

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- Definition

Reflects the net amount of other additions and reductions in the reserve for credit losses.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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- Definition

Reflects for the period the total of the carrying amount of the commercial, industrial and residential land and buildings sold plus certain overhead and other costs incurred to place the real estate in saleable condition, capitalized interest costs in the properties sold, and inventory impairment losses recognized. This element would most likely be used by an entity whose principal activities involve real estate or which has significant real estate operations.

+ References

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-Name Accounting Standards Codification

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-Paragraph 2

-Subparagraph (SX 210.5-03.2)

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- Definition

For loans held as assets for which the fair value option has been elected, this item represents the difference between the aggregate fair value and the aggregate unpaid principal balance of those loans that are 90 days or more past due, in nonaccrual status, or both.

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- Definition

Amount of allowance for credit losses related to recorded investment.

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-SubTopic 10

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-Paragraph 15

-Subparagraph (a)(3)

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- Definition

Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789

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-Name Regulation S-X (SX)

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- Definition

Carrying amount of mortgage loans to individuals not classified as held for investment but are held-for-sale.

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- Definition

Gross amount of real estate as of the balance sheet date.

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- Definition

The net Increase or Decrease in fair value as a result of other changes that are not additions, disposals, or a result of change in the inputs, assumptions, or model used to calculate the fair value of servicing assets.

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