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Loans and Allowance for Loan Losses - Impaired Loans (Detail) (USD $) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012 | Dec. 31, 2012
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | $ 12,456,000 |  | $ 12,456,000 |  | $ 20,038,000
Impaired loans, Unpaid Contractual Principal Balance | 55,253,000 |  | 55,253,000 |  | 69,166,000
Recorded Principal Balance, with no related allowance | 7,877,000 |  | 7,877,000 |  | 11,752,000
Impaired loans, Recorded Principal Balance | 50,277,000 |  | 50,277,000 |  | 57,279,000
Impaired loans, Related Allowance | 15,063,000 |  | 15,063,000 |  | 17,189,000
Average Recorded Principal Balance, with no related allowance | 9,199,000 | 16,027,000 |  |  |
Impaired Loans, Third Quarter Average Recorded Principal Balance | 51,976,000 | 57,418,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 10,270,000 | 18,024,000 |
Impaired loans, Year-To-Date Average Recorded Principal Balance |  |  | 53,233,000 | 62,328,000 |
Unpaid Contractual Principal Balance, with related allowance | 42,797,000 |  | 42,797,000 |  | 49,128,000
Recorded Principal Balance, with related allowance | 42,400,000 |  | 42,400,000 |  | 45,527,000
Impaired loans, Related Allowance | 15,063,000 |  | 15,063,000 |  | 17,189,000
Impaired Loans, Average Recorded Principal Balance | 42,777,000 | 41,391,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 42,963,000 | 44,304,000 |
Commercial and Industrial [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 2,632,000 |  | 2,632,000 |  | 1,926,000
Recorded Principal Balance, with no related allowance | 1,063,000 |  | 1,063,000 |  | 1,617,000
Impaired loans, Related Allowance | 1,035,000 |  | 1,035,000 |  | 924,000
Average Recorded Principal Balance, with no related allowance | 1,170,000 | 3,209,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 1,378,000 | 3,521,000 |
Unpaid Contractual Principal Balance, with related allowance | 2,002,000 |  | 2,002,000 |  | 3,221,000
Recorded Principal Balance, with related allowance | 1,941,000 |  | 1,941,000 |  | 1,926,000
Impaired loans, Related Allowance | 1,035,000 |  | 1,035,000 |  | 924,000
Impaired Loans, Average Recorded Principal Balance | 1,764,000 | 3,528,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 1,990,000 | 3,406,000 |
Commercial Vacant Land, Land Development, and Residential Construction [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 1,200,000 |  | 1,200,000 |  | 2,356,000
Recorded Principal Balance, with no related allowance | 804,000 |  | 804,000 |  | 1,401,000
Impaired loans, Related Allowance | 1,216,000 |  | 1,216,000 |  | 1,367,000
Average Recorded Principal Balance, with no related allowance | 907,000 | 1,480,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 1,148,000 | 1,959,000 |
Unpaid Contractual Principal Balance, with related allowance | 4,557,000 |  | 4,557,000 |  | 2,333,000
Recorded Principal Balance, with related allowance | 4,418,000 |  | 4,418,000 |  | 2,219,000
Impaired loans, Related Allowance | 1,216,000 |  | 1,216,000 |  | 1,367,000
Impaired Loans, Average Recorded Principal Balance | 4,466,000 | 2,981,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 3,158,000 | 3,529,000 |
Commercial Real Estate - Owner Occupied [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 575,000 |  | 575,000 |  | 2,368,000
Recorded Principal Balance, with no related allowance | 347,000 |  | 347,000 |  | 1,557,000
Impaired loans, Related Allowance | 901,000 |  | 901,000 |  | 1,388,000
Average Recorded Principal Balance, with no related allowance | 865,000 | 3,391,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 1,159,000 | 3,535,000 |
Unpaid Contractual Principal Balance, with related allowance | 2,368,000 |  | 2,368,000 |  | 4,307,000
Recorded Principal Balance, with related allowance | 2,310,000 |  | 2,310,000 |  | 3,626,000
Impaired loans, Related Allowance | 901,000 |  | 901,000 |  | 1,388,000
Impaired Loans, Average Recorded Principal Balance | 2,330,000 | 4,120,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 2,810,000 | 5,235,000 |
Commercial Real Estate - Non-Owner Occupied [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 5,135,000 |  | 5,135,000 |  | 9,984,000
Recorded Principal Balance, with no related allowance | 4,108,000 |  | 4,108,000 |  | 5,492,000
Impaired loans, Related Allowance | 9,785,000 |  | 9,785,000 |  | 11,773,000
Average Recorded Principal Balance, with no related allowance | 4,651,000 | 5,832,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 4,878,000 | 6,850,000 |
Unpaid Contractual Principal Balance, with related allowance | 28,358,000 |  | 28,358,000 |  | 33,818,000
Recorded Principal Balance, with related allowance | 28,346,000 |  | 28,346,000 |  | 32,964,000
Impaired loans, Related Allowance | 9,785,000 |  | 9,785,000 |  | 11,773,000
Impaired Loans, Average Recorded Principal Balance | 28,789,000 | 25,220,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 30,216,000 | 23,085,000 |
Commercial Real Estate - Multi-Family and Residential Rental [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 1,008,000 |  | 1,008,000 |  | 1,188,000
Recorded Principal Balance, with no related allowance | 337,000 |  | 337,000 |  | 413,000
Impaired loans, Related Allowance | 923,000 |  | 923,000 |  | 1,408,000
Average Recorded Principal Balance, with no related allowance | 425,000 | 918,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 487,000 | 841,000 |
Unpaid Contractual Principal Balance, with related allowance | 2,820,000 |  | 2,820,000 |  | 4,471,000
Recorded Principal Balance, with related allowance | 2,752,000 |  | 2,752,000 |  | 3,923,000
Impaired loans, Related Allowance | 923,000 |  | 923,000 |  | 1,408,000
Impaired Loans, Average Recorded Principal Balance | 2,639,000 | 4,748,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 2,973,000 | 8,306,000 |
Commercial Loans [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 10,550,000 |  | 10,550,000 |  | 17,822,000
Impaired loans, Unpaid Contractual Principal Balance | 50,655,000 |  | 50,655,000 |  | 65,972,000
Recorded Principal Balance, with no related allowance | 6,659,000 |  | 6,659,000 |  | 10,480,000
Impaired loans, Recorded Principal Balance | 46,426,000 |  | 46,426,000 |  | 55,138,000
Impaired loans, Related Allowance | 13,860,000 |  | 13,860,000 |  | 16,860,000
Average Recorded Principal Balance, with no related allowance | 8,018,000 | 14,830,000 |  |  |
Impaired Loans, Third Quarter Average Recorded Principal Balance | 48,006,000 | 55,427,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 9,050,000 | 16,706,000 |
Impaired loans, Year-To-Date Average Recorded Principal Balance |  |  | 50,197,000 | 60,267,000 |
Unpaid Contractual Principal Balance, with related allowance | 40,105,000 |  | 40,105,000 |  | 48,150,000
Recorded Principal Balance, with related allowance | 39,767,000 |  | 39,767,000 |  | 44,658,000
Impaired loans, Related Allowance | 13,860,000 |  | 13,860,000 |  | 16,860,000
Impaired Loans, Average Recorded Principal Balance | 39,988,000 | 40,597,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 41,147,000 | 43,561,000 |
Retail Home Equity and Other [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 508,000 |  | 508,000 |  | 580,000
Recorded Principal Balance, with no related allowance | 464,000 |  | 464,000 |  | 483,000
Impaired loans, Related Allowance | 102,000 |  | 102,000 |  | 204,000
Average Recorded Principal Balance, with no related allowance | 466,000 | 482,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 474,000 | 603,000 |
Unpaid Contractual Principal Balance, with related allowance | 322,000 |  | 322,000 |  | 423,000
Recorded Principal Balance, with related allowance | 293,000 |  | 293,000 |  | 394,000
Impaired loans, Related Allowance | 102,000 |  | 102,000 |  | 204,000
Impaired Loans, Average Recorded Principal Balance | 309,000 | 291,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 339,000 | 259,000 |
Retail 1-4 Family Mortgages [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 1,398,000 |  | 1,398,000 |  | 1,636,000
Recorded Principal Balance, with no related allowance | 754,000 |  | 754,000 |  | 789,000
Impaired loans, Related Allowance | 1,101,000 |  | 1,101,000 |  | 125,000
Average Recorded Principal Balance, with no related allowance | 715,000 | 715,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 746,000 | 715,000 |
Unpaid Contractual Principal Balance, with related allowance | 2,370,000 |  | 2,370,000 |  | 555,000
Recorded Principal Balance, with related allowance | 2,340,000 |  | 2,340,000 |  | 475,000
Impaired loans, Related Allowance | 1,101,000 |  | 1,101,000 |  | 125,000
Impaired Loans, Average Recorded Principal Balance | 2,480,000 | 503,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | 1,477,000 | 484,000 |
Retail Loans [Member] |  |  |  |  |
Impaired Loans By Type [Line Items] |  |  |  |  |
Unpaid Contractual Principal Balance, with no related allowance | 1,906,000 |  | 1,906,000 |  | 2,216,000
Impaired loans, Unpaid Contractual Principal Balance | 4,598,000 |  | 4,598,000 |  | 3,194,000
Recorded Principal Balance, with no related allowance | 1,218,000 |  | 1,218,000 |  | 1,272,000
Impaired loans, Recorded Principal Balance | 3,851,000 |  | 3,851,000 |  | 2,141,000
Impaired loans, Related Allowance | 1,203,000 |  | 1,203,000 |  | 329,000
Average Recorded Principal Balance, with no related allowance | 1,181,000 | 1,197,000 |  |  |
Impaired Loans, Third Quarter Average Recorded Principal Balance | 3,970,000 | 1,991,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with no related allowance |  |  | 1,220,000 | 1,318,000 |
Impaired loans, Year-To-Date Average Recorded Principal Balance |  |  | 3,036,000 | 2,061,000 |
Unpaid Contractual Principal Balance, with related allowance | 2,692,000 |  | 2,692,000 |  | 978,000
Recorded Principal Balance, with related allowance | 2,633,000 |  | 2,633,000 |  | 869,000
Impaired loans, Related Allowance | 1,203,000 |  | 1,203,000 |  | 329,000
Impaired Loans, Average Recorded Principal Balance | 2,789,000 | 794,000 |  |  |
Year-To-Date Average Recorded Principal Balance, with related allowance |  |  | $ 1,816,000 | $ 743,000 |

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