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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (41)	$ (128)	$ (181)	$ (232)
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(28)	(27)	(80)	(78)
All Other Futures Contracts, Options and equities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		12	(29)	18	(24)
Convertible securities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[1]	(1)	1	2	1
Investment And Embedded Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(17)	(55)	(60)	(101)
Futures contracts on equities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[2]	(21)	(75)	(116)	(132)
Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(24)	(73)	(121)	(131)
Other derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (3)	$ 2	$ (5)	$ 1

[1] Includes embedded derivatives.

[2] Related to MRB book of business.