Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative [Line Items]
Net gain/(loss) recognized in income	$ 21	$ (31)	$ (96)	$ 4
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	20	21		121
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(4)	(18)	(20)	(30)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(1)	(45)	(86)	(112)
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	2	(1)	(1)	2
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		8	8	18
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	$ 4	$ 4	$ 3	$ 5