Derivative Instruments (Total Fair Value Of Company's Derivative Assets And Liabilities By Instrument And Balance Sheet Location, Before Counterparty Netting) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments			$ 58,640
Notional Amount Outstanding, Total derivatives	55,806		58,640
Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value			(3,425)	[1]
Derivative liabilities, Total derivatives	(3,462)	[2]	(3,425)	[1]
Derivative Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value			102	[1]
Derivative assets, Total derivatives	93	[2]	102	[1]
Insured Credit Default Swaps [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	44,705		47,320
Insured Credit Default Swaps [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(2,960)	[2]	(2,858)	[1]
Insured Credit Default Swaps [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]
Insured Swaps [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	5,675		5,817
Insured Swaps [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(8)	[2]	(8)	[1]
Insured Swaps [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
Non-Insured Credit Default Swaps [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	5		10
Non-Insured Credit Default Swaps [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value		[2]
Non-Insured Credit Default Swaps [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	1,604		1,637
Interest Rate Swaps [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(269)	[2]	(290)	[1]
Interest Rate Swaps [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	85	[2]	94	[1]
Interest Rate Swaps-VIE [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	2,728		2,728
Interest Rate Swaps-VIE [Member] | Derivative Liabilities-VIE [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(127)	[2]	(141)	[1]
Interest Rate Swaps-VIE [Member] | Other Assets VIE [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
Interest Rate Swaps-Embedded [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	468		483
Interest Rate Swaps-Embedded [Member] | Medium-Term Notes [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value	8	[2]	8	[1]
Derivative Liabilities, Not designated, Fair Value	(37)	[2]	(35)	[1]
Currency Swap [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	19		40
Currency Swap [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value		[2]	(3)	[1]
Currency Swap [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
Currency Swaps-VIE [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	107		110
Currency Swaps-VIE [Member] | Derivative Liabilities-VIE [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(23)	[2]	(21)	[1]
Currency Swaps-VIE [Member] | Other Assets VIE [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
All Other [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	195		195
All Other [Member] | Derivative Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value	(38)	[2]	(68)	[1]
All Other [Member] | Other Assets [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
All Other-VIE [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	280		280
All Other-VIE [Member] | Derivative Liabilities-VIE [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value		[2]
All Other-VIE [Member] | Other Assets VIE [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]
All Other-Embedded [Member]
Derivative [Line Items]
Derivative Instruments, Not designated as hedging instruments	20		20
All Other-Embedded [Member] | Derivative Liabilities, Other Investments [Member]
Derivative [Line Items]
Derivative Liabilities, Not designated, Fair Value		[2]	(1)	[1]
All Other-Embedded [Member] | Derivative Assets, Other Investments [Member]
Derivative [Line Items]
Derivative Assets, Not designated, Fair Value		[2]		[1]

[1] In accordance with the accounting guidance for derivative instruments and hedging activities, the balance sheet location of the Company's embedded derivative instruments is determined by the location of the related host contract

[2] In accordance with the accounting guidance for derivative instruments and hedging activities, the balance sheet location of the Company's embedded derivative instruments is determined by the location of the related host contract.