Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Net gain/(loss) recognized in income	$ (27)	$ (41)	$ (84)	$ (117)
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	6	(6)	(16)	(20)
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(3)	(2)	(34)	(16)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(9)	(35)	(5)	(85)
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(18)	(1)	(19)	(3)
Foreign Exchange And Other Derivative Financial Instruments Attributable To V I E [Member] | Interest Rate Swaps V I E [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income		0	0	8
Foreign Exchange And Other Derivative Financial Instruments Attributable To V I E [Member] | Currency Swaps Vie [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	$ (3)	$ 3	$ (10)	$ (1)