Loans and Allowance for Loan Losses - Additional Information (Detail) (USD $)	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Proceeds from sales of loans held for sale	$ 177,335,000	$ 150,116,000
Non-accrual loans	27,389,000		25,581,000
Restructured loans	8,400,000		6,000,000
Loans 90 days past due and accruing	4,160,000		5,998,000
Commitments to lend to borrowers with loan modifications classified as TDR's	$ 1,200,000	$ 2,000

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 40

-Section 50

-Paragraph 4

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- Definition

Financing receivables that are equal to or greater than 90 days past due.

+ References

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-Name Accounting Standards Codification

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- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 40

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-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6951948&loc=d3e18794-111554

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Subparagraph b.

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- Definition

The cash inflow resulting from the sale of loans classified as held-for-sale, including proceeds from loans sold through mortgage securitization.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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