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

Available-for-sale, Securities in Unrealized Loss Positions, Severity Rate

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Carrying amount as of the balance sheet date of interest earned but not received on available-for-sale debt securities.

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Carrying amount as of the balance sheet date of interest earned but not received on held-to-maturity debt securities.

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Number of credit rating categories, highest

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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

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-Publisher FASB
-Name Accounting Standards Codification
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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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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.

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