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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 | 12 Months Ended
--- | ---
Dec. 31, 2015 | Dec. 31, 2014
Financing Receivable, Impaired [Line Items] |  |
With a related allowance recorded, Recorded Investment | $ 618 | $ 63
With a related allowance recorded, Unpaid Principal Balance | 1,468 | 63
With a related allowance recorded, Related Allowance | 37 | 54
Without a related allowance recorded, Recorded Investment | 45,032 | 43,914
Without a related allowance, Unpaid Principal Balance | 50,286 | 53,785
Without a related allowance recorded, Related Allowance | 0 | 0
Impaired financing receivables | 45,650 | 43,977
Impaired Financing Receivable, Unpaid Principal Balance, Total | 51,754 | 53,848
Impaired Financing Receivable, Related Allowance, Total | 37 | 54
With a related allowance recorded, Average Recorded Investment | 956 | 72
With a related allowance recorded, Interest Income Recognized | 7 | 6
Without a related allowance recorded, Average Recorded Investment | 46,638 | 44,978
Without a related allowance recorded, Interest Income Recognized | 1,741 | 1,550
Impaired Financing Receivable, Average Recorded Investment, Total | 47,594 | 45,050
Impaired Financing Receivable, Interest Income Recognized, Total | 1,748 | 1,556
Commercial Real Estate |  |
Financing Receivable, Impaired [Line Items] |  |
With a related allowance recorded, Recorded Investment | 0 | 0
With a related allowance recorded, Unpaid Principal Balance | 0 | 0
With a related allowance recorded, Related Allowance | 0 | 0
Without a related allowance recorded, Recorded Investment | 12,661 | 19,890
Without a related allowance, Unpaid Principal Balance | 13,157 | 25,262
Without a related allowance recorded, Related Allowance | 0 | 0
Impaired financing receivables | 12,661 | 19,890
Impaired Financing Receivable, Unpaid Principal Balance, Total | 13,157 | 25,262
Impaired Financing Receivable, Related Allowance, Total | 0 | 0
With a related allowance recorded, Average Recorded Investment | 0 | 0
With a related allowance recorded, Interest Income Recognized | 0 | 0
Without a related allowance recorded, Average Recorded Investment | 14,622 | 20,504
Without a related allowance recorded, Interest Income Recognized | 597 | 684
Impaired Financing Receivable, Average Recorded Investment, Total | 14,622 | 20,504
Impaired Financing Receivable, Interest Income Recognized, Total | 597 | 684
Commercial and Industrial |  |
Financing Receivable, Impaired [Line Items] |  |
With a related allowance recorded, Recorded Investment | 0 | 0
With a related allowance recorded, Unpaid Principal Balance | 0 | 0
With a related allowance recorded, Related Allowance | 0 | 0
Without a related allowance recorded, Recorded Investment | 14,417 | 9,218
Without a related allowance, Unpaid Principal Balance | 15,220 | 9,449
Without a related allowance recorded, Related Allowance | 0 | 0
Impaired financing receivables | 14,417 | 9,218
Impaired Financing Receivable, Unpaid Principal Balance, Total | 15,220 | 9,449
Impaired Financing Receivable, Related Allowance, Total | 0 | 0
With a related allowance recorded, Average Recorded Investment | 0 | 0
With a related allowance recorded, Interest Income Recognized | 0 | 0
Without a related allowance recorded, Average Recorded Investment | 14,416 | 9,246
Without a related allowance recorded, Interest Income Recognized | 450 | 241
Impaired Financing Receivable, Average Recorded Investment, Total | 14,416 | 9,246
Impaired Financing Receivable, Interest Income Recognized, Total | 450 | 241
Commercial Construction |  |
Financing Receivable, Impaired [Line Items] |  |
With a related allowance recorded, Recorded Investment | 500 | 0
With a related allowance recorded, Unpaid Principal Balance | 1,350 | 0
With a related allowance recorded, Related Allowance | 3 | 0
Without a related allowance recorded, Recorded Investment | 10,998 | 7,605
Without a related allowance, Unpaid Principal Balance | 14,200 | 11,293
Without a related allowance recorded, Related Allowance | 0 | 0
Impaired financing receivables | 11,498 | 7,605
Impaired Financing Receivable, Unpaid Principal Balance, Total | 15,550 | 11,293
Impaired Financing Receivable, Related Allowance, Total | 3 | 0
With a related allowance recorded, Average Recorded Investment | 834 | 0
With a related allowance recorded, Interest Income Recognized | 0 | 0
Without a related allowance recorded, Average Recorded Investment | 10,581 | 8,145
Without a related allowance recorded, Interest Income Recognized | 329 | 227
Impaired Financing Receivable, Average Recorded Investment, Total | 11,415 | 8,145
Impaired Financing Receivable, Interest Income Recognized, Total | 329 | 227
Consumer Real Estate |  |
Financing Receivable, Impaired [Line Items] |  |
With a related allowance recorded, Recorded Investment | 116 | 43
With a related allowance recorded, Unpaid Principal Balance | 116 | 43
With a related allowance recorded, Related Allowance | 32 | 43
Without a related allowance recorded, Recorded Investment | 6,845 | 7,159
Without a related allowance, Unpaid Principal Balance | 7,521 | 7,733
Without a related allowance recorded, Related Allowance | 0 | 0
Impaired financing receivables | 6,961 | 7,202
Impaired Financing Receivable, Unpaid Principal Balance, Total | 7,637 | 7,776
Impaired Financing Receivable, Related Allowance, Total | 32 | 43
With a related allowance recorded, Average Recorded Investment | 120 | 48
With a related allowance recorded, Interest Income Recognized | 7 | 4
Without a related allowance recorded, Average Recorded Investment | 6,902 | 7,027
Without a related allowance recorded, Interest Income Recognized | 364 | 396
Impaired Financing Receivable, Average Recorded Investment, Total | 7,022 | 7,075
Impaired Financing Receivable, Interest Income Recognized, Total | 371 | 400
Other Consumer |  |
Financing Receivable, Impaired [Line Items] |  |
With a related allowance recorded, Recorded Investment | 2 | 20
With a related allowance recorded, Unpaid Principal Balance | 2 | 20
With a related allowance recorded, Related Allowance | 2 | 11
Without a related allowance recorded, Recorded Investment | 111 | 42
Without a related allowance, Unpaid Principal Balance | 188 | 48
Without a related allowance recorded, Related Allowance | 0 | 0
Impaired financing receivables | 113 | 62
Impaired Financing Receivable, Unpaid Principal Balance, Total | 190 | 68
Impaired Financing Receivable, Related Allowance, Total | 2 | 11
With a related allowance recorded, Average Recorded Investment | 2 | 24
With a related allowance recorded, Interest Income Recognized | 0 | 2
Without a related allowance recorded, Average Recorded Investment | 117 | 56
Without a related allowance recorded, Interest Income Recognized | 1 | 2
Impaired Financing Receivable, Average Recorded Investment, Total | 119 | 80
Impaired Financing Receivable, Interest Income Recognized, Total | $ 1 | $ 4

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