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, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	$ 5,794		$ 6,287
Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	1,329		1,202
Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	95		50
Futures Contracts On Money Market Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	2,467		3,910
Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	1,636		871
Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	267	[1]	254	[1]
Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	1,384	[2]	1,692	[2]
Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	250	[2]	250	[2]
Other
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	10		8
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	1,644		1,950
Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Notional Value/Payment Provision	675	[3]	277	[3]
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	309		321
Other Assets [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	12		3
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		3
Other Assets [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	6		13
Other Assets [Member] | Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	[2]	0	[2]
Other Assets [Member] | Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	2	[2]	6	[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	2		6
Other Assets [Member] | Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	0	[3]	0	[3]
Accounts Payable, Accrued Expenses, And Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	(36)		(6)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	(7)		(4)
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	(29)		(2)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	0	[1]	0	[1]
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	(21)	[2]	(60)	[2]
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	0	[2]	0	[2]
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Derivative Liability	(4)		(2)
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	(25)		(62)
Fixed Maturities Available For Sale [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset	291	[1]	302	[1]
Accounts Payable Future Policy Benefits [Member] | Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability	$ (663)	[3]	$ (427)	[3]

[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.