Commitments, contingencies, and guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)		$ (193)	$ (442)	$ 375
Foreign Exchange Future [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)		31	29	11
All Other Futures Contracts And Options [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)		9	(118)	61
Convertibles and Bonds with Warrants Attached [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	[1]	(8)	(18)	6
Investment And Embedded Derivative Instruments [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)		32	(107)	78
Guaranteed Living Benefits [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	[2]	(203)	(217)	878
Single-Stock Future [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	[3]	(8)	(164)	(555)
Options On Equity Market Indices [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)	[3]	(2)	(4)	(24)
Other Derivatives
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)		(12)	50	(2)
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Commitments Contingencies And Guarantees [Line Items]
Net realized gains (losses)		$ (225)	$ (335)	$ 297

[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.