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Allowance for Loan Losses - Narrative (Detail) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2018 USD ($) Contract | Sep. 30, 2017 USD ($) Contract | Sep. 30, 2018 USD ($) Contract | Sep. 30, 2017 USD ($) Contract | Dec. 31, 2017 USD ($)
Allowance For Loan Losses [Line Items] |  |  |  |  |
TDRs performing under the restructured terms | $ 466,000 |  | $ 466,000 |  | $ 333,000
Loans modified under TDRs | Contract |  | 0 | 1,000 | 0 |
Troubled debt restructuring loan subsequent default | 0 | $ 0 | $ 0 | $ 0 |
Troubled debt restructuring loan subsequent default period |  |  | 90 days |  |
Performing financing receivable |  |  |  |  |
Allowance For Loan Losses [Line Items] |  |  |  |  |
TDRs performing under the restructured terms | $ 269,000 |  | $ 269,000 |  | $ 282,000
Secured by 1-4 family residential | Real estate loans |  |  |  |  |
Allowance For Loan Losses [Line Items] |  |  |  |  |
Loans modified under TDRs | Contract | 1 |  |  |  |
Financing Receivable, Allowance for Credit Losses, Period Increase (Decrease) |  |  | $ 19,000 |  |

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- Definition Financing receivable modification as troubled debt restructuring that subsequently defaulted. + References No definition available. + Details
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- Definition The increase (decrease) in the allowance for credit losses related to financing receivables. + 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 (c) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
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- Definition Number of financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
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- Definition The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=82895541&loc=d3e18845-111554 + 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=84173941&loc=SL6953682-111524 + Details
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