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Debt Securities - Narrative (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2021 USD ($) security | Dec. 31, 2020 USD ($)
Schedule of Held-to-maturity Securities [Line Items] |  |
Severity rate on available-for-sale debt securities in an unrealized loss position | 5.00% |
Number of credit rating categories, highest | security | 4 |
Debt securities, available-for-sale | $ 7,390,580,000 | $ 5,337,814,000
Interest receivable, available-for-sale debt securities | 17,791,000 | 20,215,000
ACL on available-for-sale debt securities | 0 |
Debt securities, held-to-maturity | 1,128,299,000 | 189,836,000
Interest receivable, held-to-maturity debt securities | 11,664,000 | 1,728,000
ACL on held-to-maturity debt securities | 0 | 0
Past due |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt securities, available-for-sale | 0 | 0
Debt securities, held-to-maturity | $ 0 | $ 0

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- Definition Amount excluding accrued interest, 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 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 + Details
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