Commitments, Contingencies, And Guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Other derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (2)	$ (3)	$ (5)	$ (5)
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		63	(41)	91	(181)
Not Designated as Hedging Instrument [Member] | Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		147	(28)	133	(80)
Not Designated as Hedging Instrument [Member] | Options/Futures/Forward contracts on notes and bonds
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		7	12	(2)	18
Not Designated as Hedging Instrument [Member] | Convertible securities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[1]	0	(1)	0	2
Not Designated as Hedging Instrument [Member] | Investment And Embedded Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		154	(17)	131	(60)
Not Designated as Hedging Instrument [Member] | Futures contracts on equities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[2]	(89)	(21)	(35)	(116)
Not Designated as Hedging Instrument [Member] | Other derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(2)	(3)	(5)	(5)
Not Designated as Hedging Instrument [Member] | Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (91)	$ (24)	$ (40)	$ (121)

[1] Includes embedded derivatives.

[2] Related to MRB book of business.