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Investment Securities - Allowance for Credit Losses HTM (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |  |  |
Beginning balance | $ 1,618 | $ 409 | $ 2,915 | $ 0
Provision for credit loss expense | (486) | (102) | (1,183) | (62)
Securities charged-off |  |  | (600) |
Ending balance | 1,132 | 307 | 1,132 | 307
State and political subdivisions |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |  |  |
Beginning balance | 1,042 | 97 | 2,307 | 0
Provision for credit loss expense | (171) | (2) | (1,436) | 37
Securities charged-off |  |  | 0 |
Ending balance | 871 | 95 | 871 | 95
Other securities |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |  |  |
Beginning balance | 576 | 312 | 608 | 0
Provision for credit loss expense | (315) | (100) | 253 | (99)
Securities charged-off |  |  | (600) |
Ending balance | $ 261 | $ 212 | $ 261 | 212
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |  |  |
Beginning balance |  |  |  | 369
Cumulative Effect, Period of Adoption, Adjustment | State and political subdivisions |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |  |  |
Beginning balance |  |  |  | 58
Cumulative Effect, Period of Adoption, Adjustment | Other securities |  |  |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |  |  |
Beginning balance |  |  |  | $ 311

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- Definition Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446 + Details
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- Definition Amount of writeoff of investment in debt security, measured at amortized cost (held-to-maturity), charged against allowance for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + Details
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- Definition Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447 + Details
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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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