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, 2020		Jun. 30, 2020	Dec. 31, 2019		Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Future policy benefits		$ 5,955			$ 5,814
Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,550			2,579
Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,457			1,615
Convertible securities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[1]	11			5
Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Asset		33			28
Derivative, Notional Amount		4,018			4,199
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[2]	648			613
Other
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		113			63
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		761			676
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[3]	0			0
Derivative, Notional Amount	[3]	2,071			1,510
Future policy benefits		436			441
Other Assets [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Asset		12			11
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	[2]	0			0
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Asset		3			2
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		3			2
Fixed Maturities [Member] | Convertible securities
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[1]	9			4
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		(73)			(78)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(3)			(15)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(76)			(93)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[2]	(1)			(13)
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		(1)			(13)
Balance Sheet Location Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[3]	(1,318)			(897)
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value		882		$ 928	456		$ 509	$ 403	$ 452
Guaranteed Benefit Liability, Net		1,318		$ 1,372	897		$ 935	$ 815	$ 861
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	[5]	$ 882	[4]		$ 456	[6]

[1] Includes fair value of embedded derivatives.

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

[3] Includes both future policy benefits reserves of $436 million and $441 million and fair value derivative adjustment of $882 million and $456 million at September 30, 2020 and December 31, 2019, 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.

[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.

[5] The weighted average lapse and annuitization rates are determined by weighting each treaty's rates by the GLB contracts fair value.

[6] 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.