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Loans and Allowance for Loan Losses - Allowance for Loan Losses Outstanding by Impairment Methodology (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | $ 9,876 | $ 10,519
Collectively evaluated for impairment | 41,790 | 38,174
Real Estate [Member] | Non-residential Real Estate Owner Occupied [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 656 | 716
Collectively evaluated for impairment | 5,539 | 4,886
Real Estate [Member] | Non-residential Real Estate Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 751 | 1,119
Collectively evaluated for impairment | 9,768 | 9,674
Real Estate [Member] | Residential Real Estate Permanent Mortgage [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 483 | 422
Collectively evaluated for impairment | 2,743 | 2,707
Real Estate [Member] | Residential Real Estate All Other [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 2,761 | 2,160
Collectively evaluated for impairment | 6,911 | 6,462
Commercial and Financial [Member] | Non-consumer Non-real Estate [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 4,651 | 3,317
Collectively evaluated for impairment | 10,683 | 9,104
Consumer Non-real Estate [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 429 | 478
Collectively evaluated for impairment | 2,364 | 2,326
Other Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 133 | 1,812
Collectively evaluated for impairment | 2,348 | 2,233
Acquired Loans [Member] |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Individually evaluated for impairment | 12 | 495
Collectively evaluated for impairment | $ 1,434 | $ 782

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + 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 (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
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- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + 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 (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
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