Commitments, contingencies, and guarantees (Balance Sheet Locations, Fair Values In Asset Or (Liability) Position, And Notional Values/Payment Provisions Of Derivative Instruments) (Detail) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021
Derivatives, Fair Value [Line Items]
Future policy benefits		$ 13,888	$ 10,476	$ 7,837	$ 7,652
Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		3,662	4,134
Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,062	1,511
Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[1]	64	37
Investment And Embedded Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		5,788	5,682
Derivative Asset, Subject to Master Netting Arrangement, before Offset		110	112
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(136)	(139)
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[2]	1,157	939
Other
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		217	0
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,374	939
Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,631	1,595
Net Investment Hedging
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,619	1,604
Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		3,250	3,199
Derivative Asset, Subject to Master Netting Arrangement, before Offset		136	17
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(128)	53
Accounts Payable and Accrued Liabilities [Member] | Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(94)	(115)
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(42)	(24)
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	[2]	(37)	0
Accounts Payable and Accrued Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(5)	0
Accounts Payable and Accrued Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(42)	0
Accounts Payable and Accrued Liabilities [Member] | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset		0	0
Accounts Payable and Accrued Liabilities [Member] | Net Investment Hedging
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset		(128)	(53)
Other Assets [Member] | Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset		27	64
Other Assets [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset		27	18
Other Assets [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	[2]	0	33
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset		0	0
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset		0	33
Other Assets [Member] | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset		126	17
Other Assets [Member] | Net Investment Hedging
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset		10	0
Fixed Maturities [Member] | Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	[1]	56	30
Equity Securities [Member] | Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	[1]	$ 0	$ 0

[1] Includes fair value of embedded derivatives.

[2] Related to MRB book of business.