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, 2014		Dec. 31, 2013		Dec. 31, 2012
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	$ (442)		$ 375		$ (136)
Foreign Exchange Future [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	29		11		(9)
All Other Futures Contracts And Options [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(118)		61		(22)
Convertibles and Bonds with Warrants Attached [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(18)	[1]	6	[1]	25	[1]
Investment And Embedded Derivative Instruments [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(107)		78		(6)
Guaranteed Living Benefits [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(217)	[2]	878	[2]	171	[2]
Single-Stock Future [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(164)	[3]	(555)	[3]	(273)	[3]
Options On Equity Market Indices [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	(4)	[3]	(24)	[3]	(24)	[3]
Credit Default Swap [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	50		(2)		(4)
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	$ (335)		$ 297		$ (130)

[1] 1) Includes embedded derivatives.

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

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