Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	$ (44)	$ 334
Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivative		27
Gain (Loss) Recognized in Income on Hedged Item		(27)
Net Gain (Loss) Recognized in Income		(2)
Unrealized Gains (Losses) On Insured Derivatives [Member] | Insured Credit Default Swaps [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	(103)	301
Unrealized Gains (Losses) On Insured Derivatives [Member] | All Other [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	30	2
Realized Gains (Losses) And Other Settlements On Insured Derivatives [Member] | Insured Credit Default Swaps [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	12	(4)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Non-Insured Credit Default Swaps [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		(1)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swaps [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	3	10
Foreign Exchange And Other Derivative Financial Instruments [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivative		27
Gain (Loss) Recognized in Income on Hedged Item		(27)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Currency Swap [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	2	(2)
Foreign Exchange And Other Derivative Financial Instruments [Member] | All Other [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		11
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | Non-Insured Credit Default Swaps-VIE [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		(1)
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | Interest Rate Swaps-VIE [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	13	21
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | Currency Swaps-VIE [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	(1)	(2)
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | All Other-VIE [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		(1)
Interest Income (Expense) [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		$ (2)