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		Sep. 30, 2018	Dec. 31, 2017
Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		$ 2,189	$ 2,064
Cross-currency swaps
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		45	45
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		5,000	0
Options/Futures contracts on notes and bonds
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,181	1,007
Convertible securities
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[1]	13	6
Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		8,428	3,122
Fair Value, Asset		67	23
Futures contracts on equities (2)
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[2]	1,095	1,553
Other
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		389	75
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,484	1,628
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[3]	1,104	1,083
Fair Value, Asset	[3]	0	0
Fixed Maturities [Member] | Convertible securities
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[1]	12	5
Equity [Member] | Convertible securities
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[1]	0	0
Other Assets [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Asset		19	14
Other Assets [Member] | Cross-currency swaps
Derivatives, Fair Value [Line Items]
Fair Value, Asset		0	0
Other Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		26	0
Other Assets [Member] | Options/Futures contracts on notes and bonds
Derivatives, Fair Value [Line Items]
Fair Value, Asset		10	4
Other Assets [Member] | Futures contracts on equities (2)
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[2]	0	0
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Asset		5	1
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		5	1
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(17)	(27)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Cross-currency swaps
Derivatives, Fair Value [Line Items]
Fair Value, Liability		0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability		0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options/Futures contracts on notes and bonds
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(7)	(3)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(24)	(30)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on equities (2)
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[2]	(7)	(21)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(2)	(2)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(9)	(23)
Balance Sheet Location Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[3]	$ (453)	$ (550)

[1] Includes fair value of embedded derivatives.

[2] Related to GMDB and GLB blocks of business.

[3] Includes both future policy benefits reserves and fair value derivative adjustment. Note that the payment provision related to GLB is the net amount at risk. The concept of a notional value does not apply to the GLB reinsurance contracts.