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Investment Securities - Amortized Cost of Debt Securities Held-to-Maturity (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
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Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | $ 310,696 | $ 375,606
AAA/AA/A |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | 310,696 | 374,921
BBB/BB/B |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | 0 | 685
Obligations of U.S. government agencies | AAA/AA/A |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | 299,797 | 361,785
Obligations of U.S. government agencies | BBB/BB/B |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | 0 | 0
Obligations of states and political subdivisions | AAA/AA/A |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | 10,899 | 13,136
Obligations of states and political subdivisions | BBB/BB/B |  |
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items] |  |
Amortized cost, held to maturity | $ 0 | $ 685

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- Definition Amount of 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 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
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