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		Mar. 31, 2019	Dec. 31, 2018
Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		$ 2,559	$ 2,185
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		5,250	5,250
Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,080	1,046
Convertible securities
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[1]	9	11
To be announced [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		0	6
Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		8,943	8,543
Fair Value, Asset		23	43
Futures contracts on equities (3)
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[2]	537	507
Other
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		184	74
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		721	581
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[3]	1,458	1,750
Fair Value, Asset	[3]	0	0
Other Assets [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Asset		9	15
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		0	0
Other Assets [Member] | Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Fair Value, Asset		6	13
Other Assets [Member] | Futures contracts on equities (3)
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[2]	0	23
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Asset		7	2
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		7	25
Fixed Maturities [Member] | Convertible securities
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[1]	8	9
Fixed Maturities [Member] | To be announced [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability		0	0
Fair Value, Asset		0	6
Equity Securities [Member] | Convertible securities
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[1]	0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(28)	(19)
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		(195)	(115)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(24)	(19)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(247)	(153)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on equities (3)
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[2]	(12)	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Liability		0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(12)	0
Balance Sheet Location Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[3]	$ (741)	$ (861)

[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.