Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Net gain/(loss) recognized in income	$ 69	$ 398	$ 325
Unrealized Gains Losses On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	157	888	1,725
Unrealized Gains Losses On Insured Derivatives [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	0	15	52
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | Credit Default Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(28)	(413)	(1,545)
Realized Gains Losses And Other Settlements On Insured Derivatives [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	0	(31)	0
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	(108)	(78)	65
Foreign Exchange And Other Derivative Financial Instruments [Member] | Currency Swap [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	0	0	1
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member]
Derivative [Line Items]
Net gain/(loss) recognized in income	7	6	0
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	31	0	17
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	$ 10	$ 11	$ 10