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Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions |  | 3 Months Ended
--- | --- | ---
Feb. 29, 2024 | Mar. 31, 2024 | Dec. 31, 2023
Loss Contingencies [Line Items] |  |  |
Commitments to extend credit to commercial customers |  | $ 12,400 | $ 12,300
Maximum credit risk for recourse associated with loans sold under Federal National Mortgage Association Delegated Underwriting and Servicing program |  | 4,000 | 3,900
Estimate assessed losses | $ 20,400 | 1,700 |
Estimate assessed losses increase | 4,100 |  |
Estimated uninsured deposits | $ 16,300 |  |
Loss contingency expense amount |  | 29 | 197
Accrued liability |  | 226 | $ 197
Minimum [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Range of reasonably possible losses |  | 0 |
Maximum [Member] |  |  |
Loss Contingencies [Line Items] |  |  |
Range of reasonably possible losses |  | $ 25 |

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