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Commitments, Contingencies, Guarantees and Others - Other Contingencies (Details) - USD ($) $ in Millions | 3 Months Ended | 11 Months Ended
--- | --- | ---
Mar. 31, 2025 | Sep. 30, 2024
Loss Contingencies [Line Items] |  |
Loss contingency, estimate of possible loss | $ 300 |
FDIC Special Assessment |  |
Loss Contingencies [Line Items] |  |
Operating expenses | 328 | $ 289
Loss contingency, estimate of possible loss | $ 200 |

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