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Commitments and Off-Balance Sheet Risk - Additional Information (Detail) (USD $) |  |  | 9 Months Ended |
--- | --- | --- | --- | ---
Sep. 30, 2013 | Dec. 31, 2012 | Sep. 30, 2013 Maximum [Member] | Sep. 30, 2013 Minimum [Member] | Sep. 30, 2013 Interest Rate Swap Agreement [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |  |  |  |  |
Notional amount of the underlying interest rate swap agreements entered into by commercial loan customers with correspondent banks |  |  |  |  | $ 18,100,000
Net fair value of interest rate swaps entered into by commercial loan customers with correspondent banks | (2,700,000) |  |  |  |
Fees accreted into income during interest rate swap agreements years |  |  | 15 years | 4 years |
Reserve or liability balance for financial instruments with off-balance sheet risk | $ 0 | $ 0 |  |  |

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Fair value of the assets less the liabilities of a derivative or group of derivatives. + 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=28364263&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13495-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958 + Details
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