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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ 23	$ 54	$ (158)	$ (178)
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		52	(17)	(28)	(95)
Options/Futures contracts on notes and bonds
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		12	29	30	5
Convertible securities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[1]	2	(3)	4	(2)
Investment And Embedded Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		66	9	6	(92)
Futures contracts on equities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[2]	(41)	52	(157)	(80)
Other derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(2)	(7)	(7)	(6)
Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (43)	$ 45	$ (164)	$ (86)

[1] Includes embedded derivatives.

[2] Related to MRB book of business.