Expected Losses to be Paid (Details 7) (USD $)	9 Months Ended	3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended						3 Months Ended				9 Months Ended				3 Months Ended				9 Months Ended										9 Months Ended						0 Months Ended	9 Months Ended		1 Months Ended
	Sep. 30, 2013	Sep. 30, 2013 Prime first lien		Sep. 30, 2012 Prime first lien		Sep. 30, 2013 Prime first lien		Sep. 30, 2012 Prime first lien		Sep. 30, 2013 Alt-A first lien		Sep. 30, 2012 Alt-A first lien		Sep. 30, 2013 Alt-A first lien		Sep. 30, 2012 Alt-A first lien		Sep. 30, 2013 Option ARM		Sep. 30, 2012 Option ARM		Sep. 30, 2013 Option ARM		Sep. 30, 2012 Option ARM		Sep. 30, 2013 First mortgage, subprime		Sep. 30, 2012 First mortgage, subprime		Sep. 30, 2013 First mortgage, subprime		Sep. 30, 2012 First mortgage, subprime		Sep. 30, 2013 Closed end second lien and HELOCs		Sep. 30, 2012 Closed end second lien and HELOCs		Sep. 30, 2013 Closed end second lien and HELOCs		Sep. 30, 2012 Closed end second lien and HELOCs		Sep. 30, 2013 HELOCs		Sep. 30, 2012 HELOCs		Sep. 30, 2013 HELOCs		Sep. 30, 2012 HELOCs		Sep. 30, 2013 RMBS loan_file		Sep. 30, 2013 Second lien		Sep. 30, 2012 Second lien		Sep. 30, 2013 Second lien		Sep. 30, 2012 Second lien		Sep. 30, 2013 Total first lien		Sep. 30, 2012 Total first lien		Sep. 30, 2013 Total first lien		Sep. 30, 2012 Total first lien		Sep. 30, 2013 Bank of America Agreement	Apr. 14, 2011 Bank of America Agreement	Sep. 30, 2013 Bank of America Agreement Second lien	Sep. 30, 2013 Bank of America Agreement Total first lien	Sep. 30, 2013 Deutsche Bank Agreement	May 08, 2012 Deutsche Bank Agreement Covered Transactions	Sep. 30, 2013 Deutsche Bank Agreement Uninsured tranches of covered transactions Transaction	May 08, 2012 Deutsche Bank Agreement Uninsured tranches of covered transactions	Sep. 30, 2013 UBS	May 06, 2013 UBS	Sep. 30, 2013 Other	Sep. 30, 2013 Maximum Deutsche Bank Agreement Uninsured tranches of covered transactions	Jun. 21, 2013 Flagstar	Sep. 30, 2013 Flagstar	Oct. 10, 2013 Subsequent Event [Member] Deutsche Bank Agreement Uninsured tranches of covered transactions	Nov. 10, 2013 Below Investment Grade [Member] Subsequent Event [Member] Deutsche Bank Agreement	Oct. 10, 2013 Below Investment Grade [Member] Subsequent Event [Member] Deutsche Bank Agreement
Guarantor Obligations [Line Items]
Amount of Liabilities Agreed Paid by Entities Providing R and Ws for Transactions Company Provided a Financial Guaranty	$ 3,487,000,000
Cash Amount Already Received for Liabilities Agreed Paid by Entities Providing R and Ws for Transactions Company Provided a Financial Guaranty	2,421,000,000
Estimated Benefit From Loan Repurchases Related to Breaches of R and W Included in Net Expected Loss Estimates Under Agreements	492,000,000
Amount of Liabilities Agreed Paid by Entities Providing R and Ws for Transactions Company Provided a Financial Guaranty, Repurchase Amounts Prior to Settlement																																																		574,000,000	[1]
Estimated Benefit From Loan Repurchases Related to Breaches of R and W Included in Net Expected Loss Estimates	895,000,000
R&W recovered during period	476,000,000	0	[2]	0	[2]	0	[3]	0	[3]	16,000,000	[2]	3,000,000	[2]	33,000,000	[3]	67,000,000	[3]	80,000,000	[2]	81,000,000	[2]	544,000,000	[3]	157,000,000	[3]	0	[2]	0	[2]	0	[3]	0	[3]	3,000,000	[2]	3,000,000	[2]	27,000,000	[3]	88,000,000	[3]	56,000,000	[2]	8,000,000	[2]	165,000,000	[3]	76,000,000	[3]			59,000,000	[2]	11,000,000	[2]	192,000,000	[3]	164,000,000	[3]	96,000,000	[2]	84,000,000	[2]	577,000,000	[3]	224,000,000	[3]
Estimated Benefit From Loan Repurchases Related to Breaches of R and W Included in Net Expected Loss Estimates in Pursuit	419,000,000
Net par outstanding amount	6,002,000,000																																																																					1,426,000,000	1,094,000,000	2,071,000,000				850,000,000		561,000,000						294,000,000
Cash Amount Already Received for Liabilities Agreed Paid by Entities Providing R and Ws for Transactions Company Provided a Financial Guaranty	2,219,000,000																																																																					968,000,000	456,000,000	176,000,000				378,000,000		241,000,000
Estimated Benefit From Loan Repurchases Related to Breaches of R and W Included in Net Expected Loss Estimates Under Agreements, Net of Reinsurance	476,000,000																																																																						230,000,000	105,000,000				92,000,000		49,000,000
Assets held under trust for reimbursement payment	1,050,000,000																																																																						615,000,000	240,000,000				195,000,000
Financial Guaranty Insurance Contracts Principal Amount Not Covered Under Agreements	1,965,000,000
Financial Guaranty Insurance Contracts Principal Amount Already Covered Under Agreements But Company Projects Receiving Additional Amounts	841,000,000
Loss Sharing Percentage																																																																					80.00%								85.00%
Maximum Loss Up To Which Loss Sharing Percentage Applicable																																																																					6,600,000,000
Collateral Losses																																																																				3,700,000,000
Estimated Cumulative Collateral Losses																																																																				5,200,000,000											148,000,000
Loss sharing percentage, first layer																																																																									80.00%
Maximum aggregate collateral losses up to which first layer of loss sharing will be applicable																																																																									319,000,000		141,000,000
Loss sharing percentage, second layer																																																																									85.00%		60.00%
Minimum losses at which second later of loss sharing percentage becomes applicable																																																																									389,000,000		161,000,000
Maximum Loss Up To Which Second Layer of Loss Sharing Percentage Applicable																																																																									600,000,000
Number of Transactions																																																																										8
Minimum losses at which third layer of loss sharing percentage becomes applicable																																																																											185,000,000
Loss sharing percentage, third layer																																																																											100.00%
Maximum aggregate collateral losses up to which third layer of loss sharing will be applicable																																																																											248,000,000
Estimated Reimburesement Amount, Collateral Losses																																																																																		26,000,000
Increase (Decrease) in Assets Held under Trust for Reimbursement Payment																																																																																			60,000,000
Proceeds from legal settlements																																																																																105,000,000	105,000,000
Number of Defaulted Loan Files Reviewed with Breached Representations and Warranties																																																		21,700
Aggregate Loan Amount of Defaulted Loan Files Reviewed with Breached Representations and Warranties																																																		$ 6,100,000,000

[1] These amounts were paid into the relevant RMBS transactions (rather than to the Company as in most settlements) and distributed in accordance with the priority of payments set out in the relevant transaction documents. Because the Company may insure only a portion of the capital structure of a transaction, such payments will not necessarily directly benefit the Company dollar-for-dollar, especially in first lien transactions.

[2] Gross amounts recovered were $159 million and $99 million for Third Quarter 2013 and 2012, respectively.

[3] Gross amounts recovered were $794 million and $410 million for Nine Months 2013 and 2012, respectively.