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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (17)	$ (22)	$ 91	$ 68
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(2)	(7)	5	0
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		26	0	26	0
All Other Futures Contracts And Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		13	(8)	47	(25)
Convertible securities (1)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[1]	0	1	0	1
Total investment and embedded derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		37	(14)	78	(24)
GLB (1)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[1]	54	54	133	265
Futures contracts on equities (2)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[2]	(100)	(57)	(122)	(169)
Other
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(8)	(5)	2	(4)
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (54)	$ (8)	$ 13	$ 92

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

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