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Investment Securities - Investments in Debt and Equity Securities Reported Less than Historical Cost (Details) - Investments reported at less than historical cost - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020
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Schedule of Investments [Line Items] |  |
Historical cost | $ 531,607 | $ 15,368
Fair value | 523,718 | 15,019
Gross unrealized losses | $ 7,889 | $ 349
Percent of the Corporation's investments available for sale | 21.60% | 0.80%

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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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