Financial Guaranty Insurance Contracts (Details 9) (USD $)	3 Months Ended			9 Months Ended						3 Months Ended						9 Months Ended						9 Months Ended							3 Months Ended		3 Months Ended	9 Months Ended					9 Months Ended							9 Months Ended						9 Months Ended
	Sep. 30, 2012 risk		Sep. 30, 2011	Sep. 30, 2012 risk		Sep. 30, 2011		Dec. 31, 2011 risk		Sep. 30, 2012 Minimum	Sep. 30, 2012 Maximum	Sep. 30, 2012 Bank of America Agreement [Member]	Sep. 30, 2012 Deutsche Bank Agreement [Member]	Sep. 30, 2012 Manufactured Housing Loans [Member]	Jun. 30, 2012 Manufactured Housing Loans [Member]	Sep. 30, 2012 Prime first lien risk		Sep. 30, 2011 Prime first lien		Dec. 31, 2011 Prime first lien risk		Sep. 30, 2012 Alt-A first lien risk		Sep. 30, 2011 Alt-A first lien		Dec. 31, 2011 Alt-A first lien risk		Sep. 30, 2012 Total first lien loan	Sep. 30, 2012 Total first lien Bank of America Agreement [Member] Transaction	Sep. 30, 2012 Total first lien Bank of America Agreement [Member] Maximum	Sep. 30, 2012 Credit Default Swap [Member] Bank of America Agreement [Member] Transaction	Sep. 30, 2012 First Mortgage Option Adjustable Rate Mortgage [Member] risk		Sep. 30, 2011 First Mortgage Option Adjustable Rate Mortgage [Member]	Dec. 31, 2011 First Mortgage Option Adjustable Rate Mortgage [Member] risk		Sep. 30, 2012 Subprime risk		Sep. 30, 2011 Subprime		Dec. 31, 2011 Subprime risk		Sep. 30, 2012 Second lien loan	Sep. 30, 2012 Closed end second lien and HELOCs risk		Sep. 30, 2011 Closed end second lien and HELOCs		Dec. 31, 2011 Closed end second lien and HELOCs risk		Sep. 30, 2012 HELOCs risk		Sep. 30, 2011 HELOCs	Dec. 31, 2011 HELOCs risk
Financial guarantee obligations
Liability for Unpaid Claims and Claims Adjustment Expense Net Largest Single Loss														$ 31,000,000	$ 26,000,000
Estimated Period of Recoveries on Transactions Backed by Heloc and Closed End Second Lien Loans Not Subject to Bank of America or Deutsche Bank										2 years	4 years
Estimated Benefit From Loan Repurchases Related to Breaches of R and W Included in Net Expected Loss Estimates	1,100,000,000			1,100,000,000								471,000,000	660,000,000
Number of defaulted loan files reviewed																												6,800															34,200
Outstanding par of defaulted loans reviewed																												2,357,000,000															2,593,000,000
Number of loan files that breached one or more R&W																												23,200															11,000
Amount of loans to be repurchased by providers																												7,187,000,000															812,000,000
Amount of Liabilities Agreed Paid by Entities Providing R and Ws for Transactions Company Provided a Financial Guaranty	2,700,000,000
Amount of Liabilities Agreed Paid Directly to the Company by Entities Providing R and Ws for Transactions the Company Provided a Financial Guaranty	2,100,000,000
Cash Amount Already Received for Liabilities Agreed Paid by Entities Providing R and Ws for Transactions Company Provided a Financial Guaranty	1,571,000,000
Cash Expected to be Received From Liabilities Agreed Paid by Entities Providing R and Ws for Transactions the Company Provided a Financial Guaranty	489,000,000			489,000,000
Amount of Liabilities Agreed Paid Into Relevant RMBS Financial Guaranty Transactions Entities Providing R and Ws to the Company for Financial Guaranty Transactions	607,000,000
Salvage and subrogation recoverable
For all Financial Guaranty Insurance Contracts	363,000,000			363,000,000				402,000,000
Effect of Consolidating FG VIEs	(130,000,000)			(130,000,000)				(197,000,000)
Reported on Balance Sheet	233,000,000	[1]		233,000,000	[1]			205,000,000	[1]
Loss and LAE reserve
For all Financial Guaranty Insurance Contracts	630,000,000			630,000,000				858,000,000
Effect of Consolidating FG VIEs	(35,000,000)			(35,000,000)				(75,000,000)
Reported on Balance Sheet	595,000,000	[1]		595,000,000	[1]			783,000,000	[1]
Total
Benefit for R&W	1,130,000,000		1,551,000,000	1,130,000,000		1,551,000,000										4,000,000		3,000,000				159,000,000		193,000,000								607,000,000		772,000,000			104,000,000		108,000,000					136,000,000		207,000,000				120,000,000		268,000,000
Rollforward of Estimated Benefit from Recoveries of Representation and Warranty Breaches, Net of Reinsurance
Future Net R&W Benefit at the beginning of the period				1,435,000,000		1,601,000,000										3,000,000		1,000,000				203,000,000		81,000,000								714,000,000		309,000,000			101,000,000		27,000,000					224,000,000		179,000,000				190,000,000		1,004,000,000
R&W Development and Accretion of Discount	12,000,000		159,000,000	83,000,000		930,000,000										1,000,000		2,000,000				23,000,000		112,000,000								50,000,000		531,000,000			3,000,000		81,000,000					0		37,000,000				6,000,000		167,000,000
R&W Recovered				(388,000,000)	[2]	(980,000,000)	[2]									0		0	[2]			67,000,000		0	[2]							(157,000,000)	[2]	68,000,000			0	[2]	0	[2]				(88,000,000)	[2]	(9,000,000)	[2]			(76,000,000)	[2]	903,000,000
Future Net R&W Benefit at the end of the period	1,130,000,000		1,551,000,000	1,130,000,000		1,551,000,000										4,000,000		3,000,000				159,000,000		193,000,000								607,000,000		772,000,000			104,000,000		108,000,000					136,000,000		207,000,000				120,000,000		268,000,000
Gross R&W amounts recovered				411,000,000		1,108,000,000
Number of Risks as of the end of the period with R&W Benefit Recorded (in policies)	42	[3]		42	[3]			59	[3]							1	[3]			1	[3]	19	[3]			22	[3]					9	[3]		12	[3]	5	[3]			5	[3]		4	[3]			4	[3]	4	[3],[4]		15	[3],[4]
Debt Service of Policies with R&W Benefit Recorded as of the end of the period	3,586,000,000			3,586,000,000				7,480,000,000								36,000,000				42,000,000		1,414,000,000				1,733,000,000						912,000,000			1,460,000,000		813,000,000				906,000,000			237,000,000				361,000,000		174,000,000	[4]		2,978,000,000	[4]
Breakdown of the development and accretion amount
Inclusion of new deals with breaches of R&W during period	0		1,000,000	(5,000,000)		108,000,000
Change in recovery assumptions as the result of additional file review and recovery success	0		43,000,000	70,000,000		242,000,000
Estimated increase (decrease) in defaults that will result in additional breaches	10,000,000		(23,000,000)	10,000,000		11,000,000
Results of settlements	0		130,000,000	0		560,000,000
Accretion of discount on balance	2,000,000		8,000,000	8,000,000		9,000,000
Total	12,000,000		159,000,000	83,000,000		930,000,000										1,000,000		2,000,000				23,000,000		112,000,000								50,000,000		531,000,000			3,000,000		81,000,000					0		37,000,000				6,000,000		167,000,000
Additional information related to Representations and Warranties
Number of transactions insured executed as financial guarantees																													20		1
Cumulative collateral losses																													2,800,000,000	6,600,000,000	100,000,000
Cumulative projected collateral losses																													4,900,000,000		200,000,000
Recovery payments received				(388,000,000)	[2]	(980,000,000)	[2]									0		0	[2]			67,000,000		0	[2]							(157,000,000)	[2]	68,000,000			0	[2]	0	[2]				(88,000,000)	[2]	(9,000,000)	[2]			(76,000,000)	[2]	903,000,000
Eligible assets in trust for payment of reimbursement																													$ 1,000,000,000

[1] The remaining benefit for R&W is not recorded on the balance sheet until the expected loss, net of R&W, exceeds unearned premium reserve.

[2] Gross amounts recovered were $411 million and $1,108 million in Nine Months 2012 and 2011, respectively.

[3] A risk represents the aggregate of the financial guaranty policies that share the same revenue source for purposes of making debt service payments.

[4] The decline in number of HELOC risks and debt service relates to the final payment from Bank of America for covered HELOC transactions and due to fundings from an R&W provider.