Commitments, Contingencies, And Guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	$ 79	$ 27
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	4	14
All Other Futures Contracts And Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	13	(8)
Investment And Embedded Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	17	6
Guaranteed Minimum Income Benefit [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	38	93
Future contracts on equities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	22	(74)
Other Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	2	2
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	$ 62	$ 21