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Debt Securities - Narrative (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2020 USD ($) security | Dec. 31, 2019 USD ($)
Investments, Debt and Equity Securities [Abstract] |  |
Debt securities pledged as collateral | $ 2,169,967,000 | $ 1,475,752,000
Severity rate on available-for-sale debt securities in an unrealized loss position | 5.00% |
Number of credit rating categories, highest | security | 4 |
Interest receivable, available-for-sale debt securities | $ 20,215,000 |
ACL on available-for-sale debt securities | 0 |
Interest receivable, held-to-maturity debt securities | 1,728,000 |
ACL on held-to-maturity debt securities | $ 0 |

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- Definition Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 9 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aaa) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 + Details
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