Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	$ (40)	$ 715	$ 1,019	$ (1,301)
Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivative		(8)	25	(4)
Gain (Loss) Recognized in Income on Hedged Item		8	(25)	4
Net Gain (Loss) Recognized in Income		(2)	(3)	(7)
Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivative	(12)	(8)	25	(6)
Gain (Loss) Recognized in Income on Hedged Item	12	8	(25)	6
Currency Swap [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivative				2
Gain (Loss) Recognized in Income on Hedged Item				(2)
Unrealized Gains (Losses) On Insured Derivatives [Member] | Insured Credit Default Swaps [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	(40)	756	1,463	(516)
Unrealized Gains (Losses) On Insured Derivatives [Member] | All Other [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	7	20	10	(15)
Realized Gains (Losses) And Other Settlements On Insured Derivatives [Member] | Insured Credit Default Swaps [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	12	(53)	(420)	(599)
Foreign Exchange and Other Derivative Financial Instruments [Member] | Interest Rate Swaps [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	(26)	(128)	(76)	(178)
Foreign Exchange and Other Derivative Financial Instruments [Member] | Currency Swap [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	1	4	1	(3)
Foreign Exchange and Other Derivative Financial Instruments [Member] | All Other [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		(6)	11	(7)
Foreign Exchange and Other Derivative Financial Instruments [Member] | Non-Insured Credit Default Swaps [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income			(1)	(1)
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | Interest Rate Swaps-VIE [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	8	(25)	39	24
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | Currency Swaps-VIE [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	(2)	(2)	(5)	(4)
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 Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		154	(1)	4
Net Gains (Losses) On Financial Instruments At Fair Value And Foreign Exchange-VIE [Member] | All Other-VIE [Member] | Not Designated As Hedging Instrument [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		(5)	(2)	(6)
Interest Income (Expense) [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income		$ (2)	$ (3)	$ (7)