Derivative Instruments (Effect Of Derivative Instruments On Consolidated Statements Of Operations) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	$ 1,445	$ (2,960)	$ (912)
Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) Recognized in Income on Derivative	12	(6)	(42)
Gain (Loss) Recognized in Income on Hedged Item	(12)	6	41
Net Gain (Loss) Recognized in Income	(3)	(9)	(6)
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	1,847	(389)	(596)
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	22	(52)	(13)
Unrealized Gains (Losses) On Insured Derivatives [Member] | Insured Swaps [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	1		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	(406)	(2,371)	(162)
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)	(2)	(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	(75)	(193)	(138)
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	12	(8)	(42)
Gain (Loss) Recognized in Income on Hedged Item	(12)	8	41
Net Gain (Loss) Recognized in Income			(1)
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)	(1)	10
Foreign Exchange And Other Derivative Financial Instruments [Member] | 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)
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	(6)	(17)
Foreign Exchange And Other Derivative Financial Instruments [Member] | Credit Linked Notes [Member] | Not Designated As Hedging Instruments [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income			18
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)	12	(24)
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	55	53	25
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	(4)	(3)
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	(2)	(8)	(16)
Interest Income (Expense) [Member] | Interest Rate Swaps [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Net Gain (Loss) Recognized in Income	$ (3)	$ (9)	$ (5)