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, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		$ 1,915	$ 5,794
Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,029	1,329
Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		95	95
Futures Contracts On Money Market Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		0	2,467
Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		751	1,636
Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[1]	40	267
Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[2]	1,197	1,384
Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[2]	0	250
Other
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		15	10
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision		1,212	1,644
Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	[3]	1,155	675
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		43	309
Other Assets [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		7	12
Other Assets [Member] | Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0	0
Other Assets [Member] | Futures Contracts On Money Market Instruments [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		5	6
Other Assets [Member] | Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	0	0
Other Assets [Member] | Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[2]	0	2
Other Assets [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Asset		0	0
Other Assets [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset		0	2
Other Assets [Member] | Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[3]	0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(13)	(36)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(11)	(7)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures Contracts On Money Market Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(2)	(29)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[1]	0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[2]	(4)	(21)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[2]	0	0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Liability		(6)	(4)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability		(10)	(25)
Fixed Maturities Available For Sale [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	[1]	31	291
Accounts Payable Future Policy Benefits [Member] | Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	[3]	$ (888)	$ (663)

[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.