Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Net gain/(loss) recognized in income	$ (15)	$ 69	$ 398
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	21	157	888
Unrealized Gains Losses On Insured Derivatives [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	0	0	15
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(40)	(28)	(413)
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	0	0	(31)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(11)	(108)	(78)
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(2)	7	6
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	31	0
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	$ 9	$ 10	$ 11