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Loans and Related Allowance for Loan and Lease Losses - Troubled Debt Restructurings Subsequently Defaulted (Detail) | 3 Months Ended | 9 Months Ended | 12 Months Ended
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Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Commercial And Industrial [Member] |  |  |  |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 | 1 | 2 | 3 | 2 |  | 5
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $ 3,000 | $ 8,000 | $ 273,000 | $ 55,000 | $ 14,000 |  | $ 574,000
Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member] |  |  |  |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | 1 |  |  |  |  | 1 |
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $ 58,000 |  |  |  |  | $ 15,000 |
Real Estate Mortgage Portfolio Segment [Member] | Commercial Loans [Member] |  |  |  |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  |  |  |  |  |  | 1
Financing Receivable, Modifications, Subsequent Default, Recorded Investment |  |  |  |  |  |  | $ 190,000
Real Estate Construction Porfolio Segment [Member] |  |  |  |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  |  | 1 | 1 | 1 |  |
Financing Receivable, Modifications, Subsequent Default, Recorded Investment |  |  | $ 58,000 | $ 152,000 | $ 130,000 |  |
Consumer Portfolio Segment [Member] |  |  |  |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  | 1 |  | 1 |  |  |
Financing Receivable, Modifications, Subsequent Default, Recorded Investment |  | $ 8,000 |  | $ 8,000 |  |  |

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- Definition Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524 + Details
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- Definition Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524 + Details
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