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		Dec. 31, 2019	Dec. 31, 2018
Derivatives, Fair Value [Line Items]
Future policy benefits		$ 5,814	$ 5,506
Derivative, Notional Amount		4,199	8,543
Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		2,579	2,185
Cross Currency Swap [Member]
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
Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		1,615	1,046
Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		5	11
To be announced [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		0	6
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		613	507
Other
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		63	74
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount		676	581
Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Future policy benefits		441	409
Derivative, Notional Amount		1,510	1,750
Accounts Payable and Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(93)	(153)
Accounts Payable and Accrued Liabilities [Member] | Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(78)	(19)
Accounts Payable and Accrued Liabilities [Member] | Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		0	0
Accounts Payable and Accrued Liabilities [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		0	(115)
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(15)	(19)
Accounts Payable and Accrued Liabilities [Member] | Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[1]	0	0
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Liability	[2]	(13)	0
Accounts Payable and Accrued Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Liability		0	0
Accounts Payable and Accrued Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(13)	0
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		28	43
Other Assets [Member] | Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		11	15
Other Assets [Member] | Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0	0
Other Assets [Member] | Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0	0
Other Assets [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		13	13
Other Assets [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	0	23
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Asset		2	2
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		2	25
Other Assets [Member] | Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Derivative Asset	[3]	0	0
Accounts Payable Future Policy Benefits [Member] | Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Derivative Liability	[3]	(897)	(861)
Available-for-sale Securities [Member] | Convertible Securities [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	4	9
Available-for-sale Securities [Member] | To be announced [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0	6
Derivative Liability		0	0
Guaranteed Minimum Income Benefit | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	[4]	$ 456	$ 452

[1] Includes fair value of embedded derivatives.

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

[3] Includes both future policy benefits reserves of $441 million and $409 million and fair value derivative adjustment of $456 million and $452 million at December 31, 2019 and 2018, respectively. Refer to Note 5 c) for additional information. 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. Refer to Note 5 c) for additional information.