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Variable Interest Entities (Narrative) (Detail) - Variable Interest Entity, Primary Beneficiary [Member] $ in Millions | 3 Months Ended
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Dec. 31, 2023 VariableInterestEntities | Sep. 30, 2023 USD ($) VariableInterestEntities | Jun. 30, 2023 USD ($) VariableInterestEntities | Mar. 31, 2023 USD ($) VariableInterestEntities | Sep. 30, 2022 USD ($) VariableInterestEntities
Variable Interest Entity [Line Items] |  |  |  |  |
Gains (losses) on the consolidation and deconsolidation | $ |  |  |  |  | $ 0
Structured Finance and International Insurance [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Number of variable interest entities deconsolidated | VariableInterestEntities | 0 | 1 | 1 | 1 | 1
Number of variable interest entities consolidated | VariableInterestEntities | 0 |  |  |  | 1
Structured Finance and International Insurance [Member] | Recorded Due To Credit Losses in AOCI [Member] |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Net realized gains (losses) related to deconsolidation | $ |  | $ (7) | $ (7) | $ (15) |

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