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, 2012		Dec. 31, 2011
Investment And Embedded Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value	$ 320		$ 427
Notional Value/Payment Provision	4,574		12,906
Other Derivative Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value	24		41
Notional Value/Payment Provision	2,558		1,973
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Foreign Exchange Future [Member]
Derivatives, Fair Value [Line Items]
Fair Value	0		7
Notional Value/Payment Provision	620		674
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Cross Currency Swap [Member]
Derivatives, Fair Value [Line Items]
Fair Value	0		0
Notional Value/Payment Provision	50		0
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures Contracts On Money Market Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value	1		7
Notional Value/Payment Provision	2,710		10,476
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Futures contracts on notes and bonds [Member]
Derivatives, Fair Value [Line Items]
Fair Value	10		(4)
Notional Value/Payment Provision	915		1,055
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options On Money Market Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Value	0		0
Notional Value/Payment Provision	0		292
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Single-Stock Future [Member]
Derivatives, Fair Value [Line Items]
Fair Value	(6)	[1]	(16)	[1]
Notional Value/Payment Provision	2,308	[1]	1,367	[1]
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Options On Equity Market Indices [Member]
Derivatives, Fair Value [Line Items]
Fair Value	30	[1]	54	[1]
Notional Value/Payment Provision	250	[1]	250	[1]
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Credit Default Swap [Member]
Derivatives, Fair Value [Line Items]
Fair Value	0		3
Notional Value/Payment Provision	0		350
Accounts Payable, Accrued Expenses, And Other Liabilities [Member] | Other
Derivatives, Fair Value [Line Items]
Fair Value	0		0
Notional Value/Payment Provision	0		6
Fixed Maturities Available For Sale [Member] | Convertibles and Bonds with Warrants Attached [Member]
Derivatives, Fair Value [Line Items]
Fair Value	309		357
Notional Value/Payment Provision	279		353
Fixed Maturities Available For Sale [Member] | Dollar Rolls [Member]
Derivatives, Fair Value [Line Items]
Fair Value	0		60
Notional Value/Payment Provision	0		56
Accounts Payable Future Policy Benefits [Member] | Guaranteed Living Benefits [Member]
Derivatives, Fair Value [Line Items]
Fair Value	(1,352)	[2]	(1,505)	[2]
Notional Value/Payment Provision	$ 1,100	[2]	$ 1,378	[2]

[1] Related to GMDB and GLB blocks of business.

[2] 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.