Expected Loss to be Paid - Narrative (Details) (USD $)	12 Months Ended				3 Months Ended			12 Months Ended
	Dec. 31, 2014 risk		Dec. 31, 2013 risk		Dec. 31, 2014		Sep. 30, 2014	Dec. 31, 2012		Sep. 12, 2014 Transaction	Oct. 10, 2013 Transaction	May 06, 2013	Apr. 14, 2011	May 08, 2012
Schedule of Expected Losses to be Paid [Line Items]
Number of risks subject to R&W recovery	29		42		29
Risks subject to R&W recovery, related net debt service amount	$ 2,100,000,000		$ 5,000,000,000		$ 2,100,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	1,169,000,000		982,000,000		1,169,000,000			677,000,000
Economic loss development after recoveries for R&W	30,000,000		(56,000,000)
Loss and loss adjustment expense reserve	799,000,000		592,000,000		799,000,000
Net par amount outstanding	403,729,000,000	[1]	459,107,000,000	[2]	403,729,000,000	[1]
Gross par outstanding	426,704,000,000		487,895,000,000		426,704,000,000
Assets	14,925,000,000		16,287,000,000		14,925,000,000
Minimum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Discount factor (as a percent)	0.00%		0.00%
Maximum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Discount factor (as a percent)	2.95%		4.44%
United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	363,294,000,000				363,294,000,000
Puerto Rico [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	4,939,000,000		5,441,000,000		4,939,000,000
Gross par outstanding	6,035,000,000		6,796,000,000		6,035,000,000
RMBS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Amount of liabilities agreed to be paid by entities providing R&W for transaction in which the Company provided insurance	4,200,000,000				4,200,000,000
RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Maximum number of payments behind to be considered performing borrower	1
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	317,000,000	[3]	712,000,000		317,000,000	[3]		1,370,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	584,000,000		493,000,000		584,000,000			282,000,000
Economic loss development after recoveries for R&W	268,000,000		156,000,000
Net par amount outstanding	9,417,000,000		13,721,000,000		9,417,000,000
RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%	[4]	15.00%	[4]	15.00%	[4]		15.00%	[4]
RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%	[4],[5]	15.00%	[4],[5]	15.00%	[4],[5]		15.00%	[4],[5]
RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%	[4]	15.00%	[4]	15.00%	[4]		15.00%	[4]
RMBS [Member] | United States [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR			10.00%	[4],[5]				10.00%	[4],[5]
RMBS [Member] | United States [Member] | Closed-end [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%	[4],[5]	10.00%	[4],[5]	15.00%	[4],[5]		10.00%	[4],[5]
RMBS [Member] | United States [Member] | Minimum [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%	[4],[5]			15.00%	[4],[5]
RMBS [Member] | United States [Member] | Maximum [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	21.80%	[4],[5]			21.80%	[4],[5]
HELOCs [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Initial period for which borrower can pay only interest payments	10 years
Percentage of expected default loans reaching amortization period	7.50%
TruPS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	4,300,000,000				4,300,000,000
Percentage of installment premiums denominated in currencies other than the U.S. dollar	72.00%
Liability for unpaid claims and claims adjustment expense, net largest single loss	23,000,000		51,000,000		23,000,000			27,000,000
Economic loss development after recoveries for R&W	28,000,000		(7,000,000)
Net par amount outstanding	4,326,000,000		4,970,000,000		4,326,000,000
Life Insurance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	3,100,000,000				3,100,000,000
Economic loss development after recoveries for R&W	(93,000,000)
Manufactured Housing Loans [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	223,000,000				223,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	25,000,000				25,000,000
Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	2,500,000,000				2,500,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	83,000,000				83,000,000
Economic loss development after recoveries for R&W	(18,000,000)
Asset-backed Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	1,800,000,000				1,800,000,000
Public Finance Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	700,000,000				700,000,000
Public Finance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	353,482,000,000		386,179,000,000		353,482,000,000
Gross par outstanding	373,360,000,000		409,890,000,000		373,360,000,000
Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liability for unpaid claims and claims adjustment expense, net largest single loss	303,000,000		264,000,000		303,000,000			7,000,000
Economic loss development after recoveries for R&W	(183,000,000)		(239,000,000)
Net par amount outstanding	322,123,000,000	[1]	352,181,000,000	[2]	322,123,000,000	[1]
Gross par outstanding	334,906,000,000		367,616,000,000		334,906,000,000
Public Finance [Member] | United States [Member] | General obligation [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	140,276,000,000		155,277,000,000		140,276,000,000
Gross par outstanding	144,714,000,000		160,751,000,000		144,714,000,000
Public Finance [Member] | Puerto Rico [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	4,900,000,000				4,900,000,000
Public Finance Stockton General Fund [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	117,000,000				117,000,000
Non-Infrastructure Public Finance [Member] | Spain [Member] | Sovereign and Sub Sovereign [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	374,000,000				374,000,000
Gross par outstanding	521,000,000				521,000,000
Non-Infrastructure Public Finance [Member] | Portugal [Member] | Sovereign and Sub Sovereign [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	102,000,000				102,000,000
Gross par outstanding	114,000,000				114,000,000
Non-Infrastructure Public Finance [Member] | Hungary [Member] | Sovereign and Sub Sovereign [Member]
Schedule of Expected Losses to be Paid [Line Items]
Gross par outstanding	529,000,000				529,000,000
Non-Infrastructure Public Finance [Member] | Spain, Hungry and Portugal [Member] | Sovereign and Sub Sovereign [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liability for unpaid claims and claims adjustment expense, net largest single loss	45,000,000				45,000,000
Economic loss development after recoveries for R&W	(5,000,000)
Deutsche Bank [Member]
Schedule of Expected Losses to be Paid [Line Items]
Assets held under trust for reimbursement payment	77,000,000				77,000,000
Number of transactions terminated	1				1					2	1
Number of transactions insured	8				8
City of Detroit [Member] | Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	2,000,000,000				2,000,000,000
City of Detroit [Member] | Public Finance [Member] | United States [Member] | Sewer [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	1,000,000,000				1,000,000,000
City of Detroit [Member] | Public Finance [Member] | United States [Member] | Water Sector [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	878,000,000				878,000,000
City of Detroit [Member] | Public Finance [Member] | United States [Member] | Water and Sewer [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	1,800,000,000				1,800,000,000
Bonds sold in tender offer, amount	677,000,000				677,000,000
Remaining principle amount after tender offer	841,000,000				841,000,000
Michigan Finance Authority [Member] | Public Finance [Member] | United States [Member] | General obligation [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	107,000,000				107,000,000
Louisville Arena Authority [Member] | Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	336,000,000				336,000,000
BIG [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	18,247,000,000		22,538,000,000		18,247,000,000
BIG [Member] | Puerto Rico [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	4,670,000,000				4,670,000,000
BIG [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	5,643,000,000		7,717,000,000		5,643,000,000
BIG [Member] | TruPS [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	1,300,000,000				1,300,000,000
Net par amount outstanding	1,333,000,000		1,722,000,000		1,333,000,000
BIG [Member] | Life Insurance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Liability for unpaid claims and claims adjustment expense, net largest single loss	161,000,000				161,000,000
Loss and loss adjustment expense reserve	598,000,000				598,000,000
BIG [Member] | Manufactured Housing Loans [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	160,000,000				160,000,000
BIG [Member] | Asset-backed Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	196,000,000				196,000,000
BIG [Member] | Public Finance Student Loan [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	101,000,000				101,000,000
BIG [Member] | Public Finance [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	7,850,000,000		9,094,000,000		7,850,000,000
BIG [Member] | Public Finance [Member] | Puerto Rico [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	4,700,000,000				4,700,000,000
BIG [Member] | Non-Infrastructure Public Finance [Member] | Hungary [Member] | Sovereign and Sub Sovereign [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	499,000,000				499,000,000
BIG [Member] | Ballantyne Re Plc and Orkney Re I I Plc [Member] | Life Insurance [Member]
Schedule of Expected Losses to be Paid [Line Items]
Number of transactions insured	2				2
Refinancing Risk on Infrastructure Transactions [Member]
Schedule of Expected Losses to be Paid [Line Items]
Financial guaranty insurance contracts, principal amount	3,000,000,000				3,000,000,000
Financial insurance guaranty, infrastructure finance, possible claims requiring payment, gross before reinsurance	1,800,000,000				1,800,000,000
Refinancing Risk on Infrastructure Transactions [Member] | Minimum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated years for recoveries of infrastructure transactions	10 years
Refinancing Risk on Infrastructure Transactions [Member] | Maximum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated years for recoveries of infrastructure transactions	35 years
First Lien [Member] | RMBS [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Number of transactions terminated	3				3
First Lien [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Increase of expected losses from estimated impact of refinements in assumptions	42,000,000		8,000,000		13,000,000		36,000,000
Default estimate liquidation period			3 years					2 years
Number of delinquent payments			2
Projected loss assumptions, CDR, plateau rate, projection period	36 months
Projected loss assumptions, Final CDR, Period for voluntary prepayments to continue	12 months
CDR, change from initial assumption	12 months
Intermediate conditional default rate (as a percent)	5.00%				5.00%
Number of scenarios weighted in estimating expected losses	5
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	232,000,000	[3]	569,000,000		232,000,000	[3]		1,082,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	595,000,000		620,000,000		595,000,000			432,000,000
Economic loss development after recoveries for R&W	226,000,000		71,000,000
First Lien [Member] | RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	15,000,000	[3]	173,000,000		15,000,000	[3]		591,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	(16,000,000)		(9,000,000)		(16,000,000)			(131,000,000)
Economic loss development after recoveries for R&W	59,000,000		98,000,000
Net par amount outstanding	407,000,000		937,000,000		407,000,000
First Lien [Member] | RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	109,000,000	[3]	118,000,000		109,000,000	[3]		109,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	303,000,000		304,000,000		303,000,000			242,000,000
Economic loss development after recoveries for R&W	7,000,000		(92,000,000)
Net par amount outstanding	4,051,000,000		6,130,000,000		4,051,000,000
First Lien [Member] | RMBS [Member] | United States [Member] | Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	2,000,000	[3]	4,000,000		2,000,000	[3]		4,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	4,000,000		21,000,000		4,000,000			6,000,000
Economic loss development after recoveries for R&W	16,000,000		(16,000,000)
Net par amount outstanding	471,000,000		541,000,000		471,000,000
First Lien [Member] | RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	106,000,000	[3]	274,000,000		106,000,000	[3]		378,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	304,000,000		304,000,000		304,000,000			315,000,000
Economic loss development after recoveries for R&W	144,000,000		81,000,000
Net par amount outstanding	2,532,000,000		3,590,000,000		2,532,000,000
First Lien [Member] | Base Scenario [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, CDR, plateau rate, projection period	36 months
Period from plateau to intermediate conditional default rate (in months)	12 months
Period of constant intermediate conditional default rate (in months)	36 months
Intermediate conditional default rate as a percentage of plateau conditional default rate	20.00%
Final conditional default rate as a percentage of plateau conditional default rate	5.00%
Final conditional default rate, shortened term	6 months
Period for which estimated defaults are attributed to loans currently delinquent or in foreclosure	36 months
Projected loss assumptions, loss severity, subsequent period	18 months
Estimated loss severity rate, one through six months (as a percent)	18 months
Loss severity (as a percent)	40.00%				40.00%
Projected loss assumptions, period to reach final loss severity rate	2 years 6 months
Projected loss assumptions, Final CDR, Period for voluntary prepayments to continue	8 years 6 months
Current conditional prepayment rate used in alternate scenario for loss estimate (as a percent)	15.00%				15.00%
First Lien [Member] | Somewhat Stressful Environment [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, CDR, plateau rate, projection period	42 months
Projected loss assumptions, period to reach final loss severity rate	4 years 6 months
Increase in the plateau period used to calculate potential change in loss estimate (in months)	6 months
Projected loss assumptions, prior period to reach final loss severity rate	2 years 6 months
First Lien [Member] | Somewhat Stressful Environment [Member] | RMBS [Member] | United States [Member] | Option Adjustable Rate Mortgage and Alt-A Mortgage [Member]
Schedule of Expected Losses to be Paid [Line Items]
Loss severity (as a percent)	45.00%				45.00%
First Lien [Member] | Somewhat Stressful Environment [Member] | RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	9,000,000
First Lien [Member] | Somewhat Stressful Environment [Member] | RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	73,000,000
First Lien [Member] | Somewhat Stressful Environment [Member] | RMBS [Member] | United States [Member] | Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	2,000,000
First Lien [Member] | Somewhat Stressful Environment [Member] | RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	29,000,000
First Lien [Member] | Somewhat Stressful Environment [Member] | Subprime [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Loss severity (as a percent)	60.00%				60.00%
First Lien [Member] | Somewhat Stressful Environment [Member] | Alt-A [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Loss severity (as a percent)	45.00%				45.00%
First Lien [Member] | More Stressful Environment [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period from plateau to intermediate conditional default rate (in months)	15 months
Projected loss assumptions, period to reach final loss severity rate	9 years
First Lien [Member] | More Stressful Environment [Member] | RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	21,000,000
First Lien [Member] | More Stressful Environment [Member] | RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	102,000,000
First Lien [Member] | More Stressful Environment [Member] | RMBS [Member] | United States [Member] | Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	7,000,000
First Lien [Member] | More Stressful Environment [Member] | RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	79,000,000
First Lien [Member] | Somewhat Less Stressful Environment [Member] | RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	12,000,000
First Lien [Member] | Somewhat Less Stressful Environment [Member] | RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	10,000,000
First Lien [Member] | Somewhat Less Stressful Environment [Member] | RMBS [Member] | United States [Member] | Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	100,000
First Lien [Member] | Somewhat Less Stressful Environment [Member] | RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	(300,000)
First Lien [Member] | Least Stressful Environment [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, CDR, plateau rate, projection period	30 months
Period from plateau to intermediate conditional default rate (in months)	9 months
Decrease in the plateau period used to calculate potential change in loss estimate (in months)	6 months
First Lien [Member] | Least Stressful Environment [Member] | RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	(26,000,000)
First Lien [Member] | Least Stressful Environment [Member] | RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	(52,000,000)
First Lien [Member] | Least Stressful Environment [Member] | RMBS [Member] | United States [Member] | Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	(1,000,000)
First Lien [Member] | Least Stressful Environment [Member] | RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, increase (decrease) in expected loss to be paid, net	(28,000,000)
First Lien [Member] | Bank of America [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Collateral losses	4,100,000,000				4,100,000,000
First Lien [Member] | Bank of America [Member] | Base Scenario [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Collateral losses	5,100,000,000				5,100,000,000
First Lien [Member] | UBS [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Agreed reimbursement of R&W, percentage												85.00%
Assets held under trust for reimbursement payment	109,000,000				109,000,000
First Lien [Member] | BIG [Member] | RMBS [Member] | United States [Member] | Option ARM [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	183,000,000		598,000,000		183,000,000
First Lien [Member] | BIG [Member] | RMBS [Member] | United States [Member] | Subprime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	1,575,000,000		1,945,000,000		1,575,000,000
First Lien [Member] | BIG [Member] | RMBS [Member] | United States [Member] | Prime [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	353,000,000		403,000,000		353,000,000
First Lien [Member] | BIG [Member] | RMBS [Member] | United States [Member] | Alt-A [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	1,841,000,000		2,728,000,000		1,841,000,000
Second Lien [Member] | Closed-end [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%				15.00%
Second Lien [Member] | RMBS [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%				15.00%
Second Lien [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period company reduced base scenario			2 months
Period company reduced optimistic scenario			3 months
Period from plateau to intermediate conditional default rate (in months)	28 months		28 months
CDR, change from initial assumption								2 months
Period of loan default estimate	5 months
Number of preceding months average liquidation rates used to estimate loan default rate	12 months
Number of months CDR is calculated by applying liquidation rates to past due balances	4 months
Stress period (in months)			34 months
Number of months of delinquent data			5 months
Period of constant conditional default rate (in months)			1 month
Conditional prepayment rate base case, average number of quarters	3 months
Number of conditional default rate curves modeled in estimating losses	3
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	85,000,000	[3]	143,000,000		85,000,000	[3]		288,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	(11,000,000)		(127,000,000)		(11,000,000)			(150,000,000)
Economic loss development after recoveries for R&W	42,000,000		85,000,000
Second Lien [Member] | RMBS [Member] | United States [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%		10.00%		15.00%
Increase in expected losses due to adjustment in recovery and maximum amortization recognition assumptions	53,000,000
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	0	[3]	45,000,000		0	[3]		150,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	(19,000,000)		(116,000,000)		(19,000,000)			(111,000,000)
Economic loss development after recoveries for R&W	45,000,000		91,000,000
Net par amount outstanding	1,738,000,000		2,279,000,000		1,738,000,000
Second Lien [Member] | RMBS [Member] | United States [Member] | Closed-end [Member]
Schedule of Expected Losses to be Paid [Line Items]
Estimated benefit from loan repurchases related to breaches of R&W included in net expected loss estimates	85,000,000	[3]	98,000,000		85,000,000	[3]		138,000,000
Liability for unpaid claims and claims adjustment expense, net largest single loss	8,000,000		(11,000,000)		8,000,000			(39,000,000)
Economic loss development after recoveries for R&W	(3,000,000)		(6,000,000)
Net par amount outstanding	218,000,000		244,000,000		218,000,000
Second Lien [Member] | RMBS [Member] | United States [Member] | Home Equity Line of Credit and Closed-end Mortgage [Member]
Schedule of Expected Losses to be Paid [Line Items]
Final CPR	15.00%				15.00%
Second Lien [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Loss recovery assumption (as a percent)	10.00%		2.00%		10.00%
Second Lien [Member] | Base Scenario [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Period from plateau to intermediate conditional default rate (in months)	28 months
Stress period (in months)	34 months
Period of constant conditional default rate (in months)	1 month
Second Lien [Member] | Base Scenario One [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Projected loss assumptions, CDR, plateau rate, projection period	4 months
Period from plateau to intermediate conditional default rate (in months)	33 months
Stress period (in months)	42 months
Increase in conditional default rate ramp down period	5 months
Second Lien [Member] | Base Scenario One [Member] | RMBS [Member] | United States [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Change in estimate for increased conditional default rate plateau period	14,000,000
Second Lien [Member] | Base Scenario One [Member] | RMBS [Member] | United States [Member] | Closed-end [Member]
Schedule of Expected Losses to be Paid [Line Items]
Change in estimate for decreased conditional default rate ramp down period	1,000,000
Second Lien [Member] | Based Scenario Two [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Stress period (in months)	24 months
Period of constant conditional default rate (in months)	1 month
Decreased conditional default rate ramp down period	18 months
Second Lien [Member] | Based Scenario Two [Member] | RMBS [Member] | United States [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Change in estimate for decreased conditional default rate ramp down period	15,000,000
Second Lien [Member] | Based Scenario Two [Member] | RMBS [Member] | United States [Member] | Closed-end [Member]
Schedule of Expected Losses to be Paid [Line Items]
Change in estimate for decreased conditional default rate ramp down period	1,000,000
Second Lien [Member] | Bank of America [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Agreed reimbursement of R&W, percentage													80.00%
Maximum loss up to which loss sharing percentage applicable													6,600,000,000
Second Lien [Member] | Bank of America [Member] | Base Scenario [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Assets held under trust for reimbursement payment	574,000,000				574,000,000
Second Lien [Member] | Guarantor Obligations, Group One [Member] | Deutsche Bank [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Maximum aggregate collateral losses up to which first layer of loss sharing will be applicable	319,000,000				319,000,000									319,000,000
Loss sharing percentage, first layer														80.00%
Second Lien [Member] | Guarantor Obligations, Group Two [Member] | Deutsche Bank [Member] | RMBS [Member] | United States [Member]
Schedule of Expected Losses to be Paid [Line Items]
Maximum aggregate collateral losses up to which first layer of loss sharing will be applicable														389,000,000
Loss sharing percentage, first layer														85.00%
Second Lien [Member] | Guarantor Obligations, Group Two [Member] | Deutsche Bank [Member] | RMBS [Member] | United States [Member] | Maximum [Member]
Schedule of Expected Losses to be Paid [Line Items]
Maximum aggregate collateral losses up to which first layer of loss sharing will be applicable														600,000,000
Second Lien [Member] | BIG [Member] | RMBS [Member] | United States [Member] | HELOCs [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	1,557,000,000		1,897,000,000		1,557,000,000
Second Lien [Member] | BIG [Member] | RMBS [Member] | United States [Member] | Closed-end [Member]
Schedule of Expected Losses to be Paid [Line Items]
Net par amount outstanding	$ 134,000,000		$ 146,000,000		$ 134,000,000

[1] Excludes $1.3 billion of loss mitigation securities insured and held by the Company as of December 31, 2014, which are primarily in the BIG category.

[2] Excludes $1.2 billion of loss mitigation securities insured and held by the Company as of December 31, 2013, which are primarily in the BIG category.

[3] See the section "Breaches of Representations and Warranties" below for eligible assets held in trust.

[4] Represents variables for most heavily weighted scenario (the “base case”).

[5] For transactions where the initial CPR is higher than the final CPR, the initial CPR is held constant and the final CPR is not used.