Financial Guaranty Insurance Losses - Loss and LAE Reserve and Salvage and Subrogation Recoverable Net of Reinsurance (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	$ 710	[1]	$ 721	[1]
Salvage and Subrogation Recoverable, net	128	[1]	154	[1]
Net Reserve (Recoverable)	582	[1]	567	[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	709		719
Salvage and Subrogation Recoverable, net	128		148
Net Reserve (Recoverable)	581		571
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	787		799
Salvage and Subrogation Recoverable, net	129		149
Net Reserve (Recoverable)	658		650
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	(78)		(80)
Salvage and Subrogation Recoverable, net	(1)		(1)
Net Reserve (Recoverable)	(77)		(79)
Other Insurance Product Line [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	1		2
Salvage and Subrogation Recoverable, net	0		6
Net Reserve (Recoverable)	1		(4)
Trust Preferred Securities (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		0
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	0		0
Triple-X Life Insurance Transaction [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	144		140
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	144		140
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	90		96
Salvage and Subrogation Recoverable, net	0		2
Net Reserve (Recoverable)	90		94
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	506		526
Salvage and Subrogation Recoverable, net	114		128
Net Reserve (Recoverable)	392		398
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	281		273
Salvage and Subrogation Recoverable, net	8		8
Net Reserve (Recoverable)	273		265
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	787		799
Salvage and Subrogation Recoverable, net	122		136
Net Reserve (Recoverable)	665		663
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	7		13
Net Reserve (Recoverable)	(7)		(13)
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	272		290
Salvage and Subrogation Recoverable, net	114		126
Net Reserve (Recoverable)	158		164
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	253		243
Salvage and Subrogation Recoverable, net	8		8
Net Reserve (Recoverable)	245		235
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	28		30
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	28		30
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	265		283
Salvage and Subrogation Recoverable, net	48		48
Net Reserve (Recoverable)	217		235
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		7
Salvage and Subrogation Recoverable, net	66		78
Net Reserve (Recoverable)	(59)		(71)
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		2
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	2		2
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	80		87
Salvage and Subrogation Recoverable, net	0		0
Net Reserve (Recoverable)	80		87
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	24		28
Salvage and Subrogation Recoverable, net	42		40
Net Reserve (Recoverable)	(18)		(12)
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	159		166
Salvage and Subrogation Recoverable, net	6		8
Net Reserve (Recoverable)	153		158
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	5		4
Salvage and Subrogation Recoverable, net	37		39
Net Reserve (Recoverable)	(32)		(35)
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	2		3
Salvage and Subrogation Recoverable, net	29		39
Net Reserve (Recoverable)	$ (27)		$ (36)

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