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Loans and Allowance for Credit Losses - Restructured Loans that are Considered to be in Default (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 USD ($) loan | Dec. 31, 2016 USD ($) loan | Dec. 31, 2015 USD ($) loan
Financing Receivable, Modifications [Line Items] |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | loan | 1 | 4 | 3
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $ | $ 2 | $ 313 | $ 97
Residential Portfolio Segment [Member] |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | loan | 0 | 4 | 3
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $ | $ 0 | $ 313 | $ 97
Loans To Individuals [Member] |  |  |
Financing Receivable, Modifications [Line Items] |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts | loan | 1 | 0 | 0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment | $ | $ 2 | $ 0 | $ 0

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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=84173941&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=84173941&loc=SL6953682-111524 + Details
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