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Investment Securities - Narrative (Details) |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Apr. 01, 2024 USD ($) | Sep. 30, 2024 USD ($) security | Jun. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) security | Sep. 30, 2023 USD ($) | Dec. 31, 2023 USD ($)
Financing Receivable, Impaired [Line Items] |  |  |  |  |  |  |
Debt securities, available-for-sale transferred to held-to-maturity | $ 2,720,000,000 |  |  |  |  |  |
Net unamortized unrealized holding (losses) gains on available for sale investment securities transferred to held to maturity | $ 537,400,000 | $ 0 |  | $ 0 | $ (537,434,000) | $ 0 |
Debt securities, available-for-sale, realized loss |  | $ 0 |  | $ 0 | 256,660,000 | 0 |
Payments to acquire investment securities available for sale |  |  | $ 1,480,000,000 |  | $ 2,255,313,000 | $ 709,932,000 |
Number of investment securities in a loss position for less than twelve months | security |  | 2 |  |  | 2 |  |
Number of investment securities in a loss position for twelve months or longer | security |  | 211 |  |  | 211 |  |
AFS allowance for credit loss |  | $ 0 |  |  | $ 0 |  |
Held-to-maturity, allowance for credit loss, measurement input |  | 0 |  |  | 0 |  |
Mortgage-backed securities issued by U.S. Government sponsored enterprises |  |  |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |  |  |
Debt securities, AFS, sold at amortized cost |  |  | 1,620,000,000 |  |  |  |
Debt securities, available-for-sale, realized loss |  |  | $ 256,700,000 |  |  |  |
Collateral Pledged |  |  |  |  |  |  |
Financing Receivable, Impaired [Line Items] |  |  |  |  |  |  |
AFS pledged to secure deposits |  | 2,470,000,000 |  |  | 2,470,000,000 |  | $ 5,190,000,000
HTM pledged to secure deposits |  | $ 2,340,000,000 |  |  | $ 2,340,000,000 |  |

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