Financial Guaranty Insurance Losses - Loss and LAE Reserve and Salvage and Subrogation Recoverable Net of Reinsurance (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	$ 721	[1]	$ 556	[1]
Salvage and Subrogation Recoverable, net	154	[1]	170	[1]
Net Reserve (Recoverable)	567	[1]	386	[1]
Financial Guarantee Insurance Product Line [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	719		554
Salvage and Subrogation Recoverable, net	148		165
Net Reserve (Recoverable)	571		389
Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	799		657
Salvage and Subrogation Recoverable, net	149		250
Net Reserve (Recoverable)	650		407
Financial Guarantee Insurance Product Line [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	80		103
Salvage and Subrogation Recoverable, net	1		85
Net Reserve (Recoverable)	79		18
Other Insurance Product Line [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	2		2
Salvage and Subrogation Recoverable, net	6		5
Net Reserve (Recoverable)	(4)		(3)
TruPS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	0		2
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	0		2
Structured Finance [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	236		145
Salvage and Subrogation Recoverable, net	2		6
Net Reserve (Recoverable)	234		139
Financial Guarantee [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	799		657
Salvage and Subrogation Recoverable, net	136		235
Net Reserve (Recoverable)	663		422
Other [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	0		0
Salvage and Subrogation Recoverable, net	13		15
Net Reserve (Recoverable)	(13)		(15)
United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	290		286
Salvage and Subrogation Recoverable, net	126		221
Net Reserve (Recoverable)	164		65
United States [Member] | Public Finance [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	243		189
Salvage and Subrogation Recoverable, net	8		8
Net Reserve (Recoverable)	235		181
Non United States [Member] | Public Finance [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	30		35
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	30		35
First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	283		276
Salvage and Subrogation Recoverable, net	48		49
Net Reserve (Recoverable)	235		227
Second Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	7		10
Salvage and Subrogation Recoverable, net	78		172
Net Reserve (Recoverable)	(71)		(162)
Prime [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	2		3
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	2		3
Alt-A [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	87		108
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	87		108
Option ARM [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	28		22
Salvage and Subrogation Recoverable, net	40		47
Net Reserve (Recoverable)	(12)		(25)
Subprime [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	166		143
Salvage and Subrogation Recoverable, net	8		2
Net Reserve (Recoverable)	158		141
Closed-end [Member] | Second Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	4		5
Salvage and Subrogation Recoverable, net	39		45
Net Reserve (Recoverable)	(35)		(40)
HELOCs [Member] | Second Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	3		5
Salvage and Subrogation Recoverable, net	39		127
Net Reserve (Recoverable)	$ (36)		$ (122)

[1] See “Components of Net Reserves (Salvage)” table for loss and LAE reserve and salvage and subrogation recoverable components.