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, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Future policy benefits		$ 5,738		$ 5,506
Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,888		2,185
Cross-currency swaps
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		0		45
Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		0		5,250
Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		853		1,046
Convertible securities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[1]	8		11
To be announced [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		0		6
Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Asset		27		43
Derivative, Notional Amount		3,749		8,543
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		582		507
Other
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		207		74
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		789		581
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[2]	0		0
Derivative, Notional Amount		1,729		1,750
Future policy benefits		426		409
Other Assets [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Asset		10		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		12		13
Other Assets [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[3]	6		23
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Asset		1		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]	5		9
Fixed Maturities [Member] | To be announced [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset				6
Fair Value, Liability				0
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		(59)		(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		0		(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		(4)		(19)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(63)		(153)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[3]	0		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		0		0
Balance Sheet Location Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[2]	(935)		(861)
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value		509	$ 403	452	$ 71	$ 125	$ 204
Guaranteed Benefit Liability, Net		935	$ 815	861	$ 453	$ 497	$ 550
Guaranteed Minimum Income Benefit [Member] | Fair Value, Recurring [Member] | Level 3
Derivatives, Fair Value [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value	[4]	$ 509		$ 452

[1] Includes fair value of embedded derivatives.

[2] Includes both future policy benefits reserves of $426 million and $409 million and fair value derivative adjustment of $509 million and $452 million at September 30, 2019 and December 31, 2018, respectively. 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.

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

[4] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value. Excluded from the table above is the portion of the GLB derivative liability classified as Future policy benefits in the Consolidated balance sheets.