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Commitments, Contingencies, And Guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Other derivative instruments |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | $ (9) | $ (2) | $ (14) | $ (7)
Not Designated as Hedging Instrument [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | (153) | 23 | (62) | (158)
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | (82) | 52 | 51 | (28)
Not Designated as Hedging Instrument [Member] | Options/Futures/Forward contracts on notes and bonds |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | (3) | 12 | (5) | 30
Not Designated as Hedging Instrument [Member] | Convertible securities |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative | [1] | 0 | 2 | 0 | 4
Not Designated as Hedging Instrument [Member] | Investment And Embedded Derivative Instruments [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | (85) | 66 | 46 | 6
Not Designated as Hedging Instrument [Member] | Futures contracts on equities |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative | [2] | (59) | (41) | (94) | (157)
Not Designated as Hedging Instrument [Member] | Other derivative instruments |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | (9) | (2) | (14) | (7)
Not Designated as Hedging Instrument [Member] | Other Derivative Instruments [Member] |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |
Gain (Loss) on Derivative |  | $ (68) | $ (43) | $ (108) | $ (164)
[1] | Includes embedded derivatives.
[2] | Related to MRB book of business.

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