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, 2019		Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ (80)		$ 79
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(15)		4
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(80)		0
All Other Futures Contracts, Options and equities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(36)		13
Convertible securities (1)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		1	[1]	0
Total investment and embedded derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(130)		17
GLB (2)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[2]	114		38
Futures contracts on equities (3)
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative	[3]	(63)		22
Other
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		(1)		2
Guaranteed Living Benefit And Other Derivative Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative		$ 50		$ 62

[1] Includes embedded derivatives.

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

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