Commitments, contingencies, and guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	$ (136)		$ (930)		$ (139)
Foreign Exchange Future [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(9)		6		21
All Other Futures Contracts And Options [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(22)		(98)		29
Convertibles and Bonds with Warrants Attached [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	25		(50)		7
Dollar Rolls [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	0		(1)		1
Investment And Embedded Derivative Instruments [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(6)		(143)		58
Guaranteed Living Benefits [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	171	[1]	(779)	[1]	(28)	[1]
Single-Stock Future [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(273)	[2]	(12)	[2]	(140)	[2]
Options On Equity Market Indices [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(24)	[2]	8	[2]	(10)	[2]
Interest Rate Swap [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	0	[2]	0	[2]	(21)	[2]
Credit Default Swap [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(4)		(4)		1
Other Derivatives
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	0	[2]	0	[2]	1	[2]
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	$ (130)		$ (787)		$ (197)

[1] Excludes foreign exchange gains (losses) related to GLB.

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