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Loans and Allowance for Loan Losses - Allowance Related to Loans Categorized as Troubled Debt Restructurings (Detail) (USD $) | Sep. 30, 2013 | Jun. 30, 2013 | Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Dec. 31, 2011
--- | --- | --- | --- | --- | --- | ---
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | $ 25,195,000 | $ 24,947,000 | $ 28,677,000 | $ 27,762,000 | $ 29,689,000 | $ 36,532,000
Commercial Loans [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 22,654,000 | 22,382,000 | 26,043,000 | 24,894,000 | 26,471,000 | 33,431,000
Retail Loans [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 2,498,000 | 2,559,000 | 2,645,000 | 2,827,000 | 3,167,000 | 3,019,000
Financing Receivable Troubled Debt Restructuring [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 14,164,000 |  | 13,097,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Commercial and Industrial [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 619,000 |  | 772,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Commercial Vacant Land, Land Development, and Residential Construction [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 1,208,000 |  | 713,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Commercial Real Estate - Owner Occupied [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 893,000 |  | 1,116,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Commercial Real Estate - Non-Owner Occupied [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 9,639,000 |  | 9,751,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Commercial Real Estate - Multi-Family and Residential Rental [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 885,000 |  | 745,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Commercial Loans [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 13,244,000 |  | 13,097,000 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Home equity and other [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 0 |  | 0 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | 1 - 4 family mortgages [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | 920,000 |  | 0 |  |  |
Financing Receivable Troubled Debt Restructuring [Member] | Retail Loans [Member] |  |  |  |  |  |
Schedule Of Financing Receivable Troubled Debt Restructurings [Line Items] |  |  |  |  |  |
Total | $ 920,000 |  | $ 0 |  |  |

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- Definition A valuation allowance for financing receivables that are expected to be uncollectible. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953423-111524 + Details
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