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Investment Securities - Pledged Securities and Concentration Narrative (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Non-government issuer |  |
Concentration of risk |  |
Securities of issuers in excess of 10% of stockholders' equity | $ 0.0 | $ 0.0
Collateral Dependent Loans |  |
Financial Instruments Owned and Pledged as Collateral |  |
Investment securities pledged as collateral | 4,400.0 | 3,800.0
Collateral Dependent Loans | Borrowing capacity |  |
Financial Instruments Owned and Pledged as Collateral |  |
Investment securities pledged as collateral | 2,400.0 | 2,100.0
Collateral Dependent Loans | Public deposits |  |
Financial Instruments Owned and Pledged as Collateral |  |
Investment securities pledged as collateral | 2,000.0 | 1,700.0
Collateral Dependent Loans | Other financial transactions |  |
Financial Instruments Owned and Pledged as Collateral |  |
Investment securities pledged as collateral | $ 49.5 | $ 19.3

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