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Securities - Additional Information (Detail) $ in Thousands | Sep. 30, 2017 USD ($) Security | Dec. 31, 2016 USD ($)
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Investments Debt And Equity Securities [Abstract] |  |
Carrying value of pledged securities | $ | $ 130,367 | $ 139,179
Number of securities in portfolio with unrealized losses | Security | 58 |

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- Definition The fair value of available-for-sale securities that serve as collateral for borrowings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5086-111524 + Details
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