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, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		$ 4,666	$ 1,915
Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[1]	7	40
Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		2,220	1,029
Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		95	95
Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		2,344	751
Futures contracts on equities
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[2]	1,316	1,197
Other
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		214	15
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,530	1,212
Guaranteed Minimum Income Benefit
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[3]	1,264	1,155
Accounts Payable and Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(54)	(13)
Accounts Payable and Accrued Liabilities [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[1]	0	0
Accounts Payable and Accrued Liabilities [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(50)	(11)
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] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(4)	(2)
Accounts Payable and Accrued Liabilities [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Liability	[2]	0	(4)
Accounts Payable and Accrued Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Liability		(13)	(6)
Accounts Payable and Accrued Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(13)	(10)
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		33	43
Other Assets [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		25	7
Other Assets [Member] | Cross Currency 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		6	5
Other Assets [Member] | Futures contracts on equities
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	1	0
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Asset		2	0
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		3	0
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]	(853)	(888)
Available-for-sale Securities [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	$ 2	$ 31

[1] (1)Includes fair value of embedded derivatives.

[2] (2) Related to GMDB and GLB blocks of business.

[3] (3) Includes both future policy benefits reserves and fair value derivative adjustment. 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.