Commitments, Contingencies, And Guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	$ (22)	$ 48	$ 68	$ (442)
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	(7)	(10)	0	(30)
All Other Futures Contracts And Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	(8)	8	(25)	(63)
Convertibles and Bonds with Warrants Attached [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	1	3	1	8
Investment And Embedded Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	(14)	1	(24)	(85)
Guaranteed Minimum Income Benefit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	54	89	265	(270)
Single-Stock Future [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	(57)	(45)	(169)	(88)
Other Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	(5)	3	(4)	1
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain Loss on Derivative	$ (8)	$ 47	$ 92	$ (357)