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		Jun. 30, 2018	Dec. 31, 2017
Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		$ 2,364	$ 2,064
Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		45	45
Options/Futures contracts on notes and bonds
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,409	1,007
Convertible securities [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		10	6	[1]
Investment And Embedded Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		3,828	3,122
Fair Value, Asset		48	23
Future contracts on equities [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[2]	1,632	1,553
Other Derivatives [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		351	75
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,983	1,628
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[3]	1,163	1,083
Fair Value, Asset	[3]	0	0
Fixed Maturities [Member] | Convertible securities [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		9	5
Equity [Member] | Convertible securities [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability		0	0
Other Assets [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Asset		33	14
Other Assets [Member] | Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		0	0
Other Assets [Member] | Options/Futures contracts on notes and bonds
Derivatives, Fair Value [Line Items]
Fair Value, Asset		6	4
Other Assets [Member] | Future contracts on equities [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[2]	32	0
Other Assets [Member] | Other Derivatives [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		18	1
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		50	1
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(36)	(27)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Cross Currency 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		(6)	(3)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Investment And Embedded Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(42)	(30)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Future contracts on equities [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[2]	0	(21)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other Derivatives [Member]
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		(2)	(23)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[3]	$ (497)	$ (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.