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Allowance for Loan Losses - Investments in Loans Considered to be Impaired and Related Information on Impaired Loans (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2015 | Jun. 30, 2014 | Jun. 30, 2015 | Jun. 30, 2014 | Dec. 31, 2014
Financing Receivable, Impaired [Line Items] |  |  |  |  |
Without a related allowance recorded, Recorded Investment | $ 44,982 |  | $ 44,982 |  | $ 43,914
Without a related allowance, Unpaid Principal Balance | 58,282 |  | 58,282 |  | 53,785
Without a related allowance recorded, Related Allowance | 0 |  | 0 |  | 0
With a related allowance recorded, Recorded Investment | 873 |  | 873 |  | 63
With a related allowance recorded, Unpaid Principal Balance | 873 |  | 873 |  | 63
Impaired Financing Receivable, Recorded Investment, Total | 45,855 |  | 45,855 |  | 43,977
Impaired Financing Receivable, Unpaid Principal Balance, Total | 59,155 |  | 59,155 |  | 53,848
Impaired Financing Receivable, Related Allowance | 608 |  | 608 |  | 54
Without a related allowance recorded, Average Recorded Investment | 45,651 | $ 46,253 | 45,274 | $ 46,719 |
Without a related allowance recorded, Interest Income Recognized | 418 | 374 | 792 | 762 |
With a related allowance recorded, Average Recorded Investment | 545 | 70 | 337 | 73 |
With a related allowance recorded, Interest Income Recognized | 2 | 1 | 3 | 3 |
Impaired Financing Receivable, Average Recorded Investment, Total | 46,196 | 46,323 | 45,611 | 46,792 |
Impaired Financing Receivable, Interest Income Recognized, Total | 420 | 375 | 795 | 765 |
Commercial Real Estate [Member] |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |
Without a related allowance recorded, Recorded Investment | 18,548 |  | 18,548 |  | 19,890
Without a related allowance, Unpaid Principal Balance | 25,698 |  | 25,698 |  | 25,262
With a related allowance recorded, Recorded Investment | 749 |  | 749 |  |
With a related allowance recorded, Unpaid Principal Balance | 749 |  | 749 |  |
Impaired Financing Receivable, Recorded Investment, Total | 19,297 |  | 19,297 |  | 19,890
Impaired Financing Receivable, Unpaid Principal Balance, Total | 26,447 |  | 26,447 |  | 25,262
Impaired Financing Receivable, Related Allowance | 567 |  | 567 |  |
Without a related allowance recorded, Average Recorded Investment | 19,733 | 21,382 | 20,455 | 21,980 |
Without a related allowance recorded, Interest Income Recognized | 158 | 159 | 322 | 329 |
With a related allowance recorded, Average Recorded Investment | 420 |  | 211 |  |
Impaired Financing Receivable, Average Recorded Investment, Total | 20,153 | 21,382 | 20,666 | 21,980 |
Impaired Financing Receivable, Interest Income Recognized, Total | 158 | 159 | 322 | 329 |
Commercial and Industrial [Member] |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |
Without a related allowance recorded, Recorded Investment | 10,125 |  | 10,125 |  | 9,218
Without a related allowance, Unpaid Principal Balance | 11,877 |  | 11,877 |  | 9,449
Impaired Financing Receivable, Recorded Investment, Total | 10,125 |  | 10,125 |  | 9,218
Impaired Financing Receivable, Unpaid Principal Balance, Total | 11,877 |  | 11,877 |  | 9,449
Without a related allowance recorded, Average Recorded Investment | 10,782 | 9,317 | 11,162 | 9,066 |
Without a related allowance recorded, Interest Income Recognized | 84 | 57 | 146 | 114 |
Impaired Financing Receivable, Average Recorded Investment, Total | 10,782 | 9,317 | 11,162 | 9,066 |
Impaired Financing Receivable, Interest Income Recognized, Total | 84 | 57 | 146 | 114 |
Construction Loans [Member] |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |
Without a related allowance recorded, Recorded Investment | 9,293 |  | 9,293 |  | 7,605
Without a related allowance, Unpaid Principal Balance | 12,983 |  | 12,983 |  | 11,293
Impaired Financing Receivable, Recorded Investment, Total | 9,293 |  | 9,293 |  | 7,605
Impaired Financing Receivable, Unpaid Principal Balance, Total | 12,983 |  | 12,983 |  | 11,293
Without a related allowance recorded, Average Recorded Investment | 8,119 | 8,279 | 6,628 | 8,301 |
Without a related allowance recorded, Interest Income Recognized | 81 | 57 | 134 | 114 |
Impaired Financing Receivable, Average Recorded Investment, Total | 8,119 | 8,279 | 6,628 | 8,301 |
Impaired Financing Receivable, Interest Income Recognized, Total | 81 | 57 | 134 | 114 |
Consumer Real Estate [Member] |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |
Without a related allowance recorded, Recorded Investment | 6,824 |  | 6,824 |  | 7,159
Without a related allowance, Unpaid Principal Balance | 7,527 |  | 7,527 |  | 7,733
With a related allowance recorded, Recorded Investment | 120 |  | 120 |  | 43
With a related allowance recorded, Unpaid Principal Balance | 120 |  | 120 |  | 43
Impaired Financing Receivable, Recorded Investment, Total | 6,944 |  | 6,944 |  | 7,202
Impaired Financing Receivable, Unpaid Principal Balance, Total | 7,647 |  | 7,647 |  | 7,776
Impaired Financing Receivable, Related Allowance | 37 |  | 37 |  | 43
Without a related allowance recorded, Average Recorded Investment | 6,891 | 7,166 | 6,943 | 7,260 |
Without a related allowance recorded, Interest Income Recognized | 91 | 100 | 186 | 203 |
With a related allowance recorded, Average Recorded Investment | 121 | 48 | 122 | 50 |
With a related allowance recorded, Interest Income Recognized | 2 | 1 | 3 | 2 |
Impaired Financing Receivable, Average Recorded Investment, Total | 7,012 | 7,214 | 7,065 | 7,310 |
Impaired Financing Receivable, Interest Income Recognized, Total | 93 | 101 | 189 | 205 |
Other Consumer [Member] |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |
Without a related allowance recorded, Recorded Investment | 192 |  | 192 |  | 42
Without a related allowance, Unpaid Principal Balance | 197 |  | 197 |  | 48
With a related allowance recorded, Recorded Investment | 4 |  | 4 |  | 20
With a related allowance recorded, Unpaid Principal Balance | 4 |  | 4 |  | 20
Impaired Financing Receivable, Recorded Investment, Total | 196 |  | 196 |  | 62
Impaired Financing Receivable, Unpaid Principal Balance, Total | 201 |  | 201 |  | 68
Impaired Financing Receivable, Related Allowance | 4 |  | 4 |  | $ 11
Without a related allowance recorded, Average Recorded Investment | 126 | 109 | 86 | 112 |
Without a related allowance recorded, Interest Income Recognized | 4 | 1 | 4 | 2 |
With a related allowance recorded, Average Recorded Investment | 4 | 22 | 4 | 23 |
With a related allowance recorded, Interest Income Recognized |  |  |  | 1 |
Impaired Financing Receivable, Average Recorded Investment, Total | 130 | 131 | 90 | 135 |
Impaired Financing Receivable, Interest Income Recognized, Total | $ 4 | $ 1 | $ 4 | $ 3 |

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