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, 2020	Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Future policy benefits		$ 5,776	$ 5,814
Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,639	2,579
Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,116	1,615
Convertible securities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[1]	5	5
Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Asset		51	28
Derivative, Notional Amount		3,760	4,199
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	[2]	514	613
Other
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		103	63
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		617	676
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[3]	0	0
Derivative, Notional Amount	[3]	2,680	1,510
Future policy benefits		450	441
Other Assets [Member] | Foreign currency forward contracts
Derivatives, Fair Value [Line Items]
Fair Value, Asset		32	11
Other Assets [Member] | Options/Futures contracts on notes, bonds, and equities
Derivatives, Fair Value [Line Items]
Fair Value, Asset		15	13
Other Assets [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[2]	17	0
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value, Asset		2	2
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Asset		19	2
Fixed Maturities [Member] | Convertible securities
Derivatives, Fair Value [Line Items]
Fair Value, Asset	[1]	4	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		(109)	(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		(32)	(15)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Total investment and embedded derivative instruments
Derivatives, Fair Value [Line Items]
Fair Value, Liability		(141)	(93)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[2]	0	(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		0	(13)
Balance Sheet Location Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Liability	[3]	(1,591)	(897)
Guaranteed Minimum Income Benefit [Member]
Derivatives, Fair Value [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value		1,141	456		$ 338	$ 452
Guaranteed Benefit Liability, Net		1,591	897		$ 741	$ 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	[4]	$ 1,141	$ 456	[5]

[1] Includes fair value of embedded derivatives.

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

[3] Includes both future policy benefits reserves of $450 million and $441 million and fair value derivative adjustment of $1,141 million and $456 million at March 31, 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] The weighted average lapse and annuitization rates are determined by weighting each treaty's rates by the GLB contracts fair value.

[5] 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.