Financial Guaranty Insurance Losses - Loss and LAE Reserve and Salvage and Subrogation Recoverable Net of Reinsurance (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net	[1]	$ 919	$ 721
Salvage and Subrogation Recoverable, net	[1]	140	154
Net Reserve (Recoverable)	[1]	779	567
Financial Guarantee Insurance And Other Product Line [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE Reserve, net		900
Financial Guarantee Insurance And Other 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		989	801
Salvage and Subrogation Recoverable, net		141	155
Net Reserve (Recoverable)		848	646
Financial Guarantee Insurance And Other 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		(70)	(80)
Salvage and Subrogation Recoverable, net		(1)	(1)
Net Reserve (Recoverable)		(69)	(79)
Public Finance [Member] | Financial Guarantee Insurance And Other 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		483	273
Salvage and Subrogation Recoverable, net		10	8
Net Reserve (Recoverable)		473	265
Trust Preferred Securities (TruPS) [Member] | Financial Guarantee Insurance And Other 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
Student Loan [Member] | Financial Guarantee Insurance And Other 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		55	64
Salvage and Subrogation Recoverable, net		0	0
Net Reserve (Recoverable)		55	64
Triple-X Life Insurance Transaction [Member] | Financial Guarantee Insurance And Other 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		140	140
Salvage and Subrogation Recoverable, net		0	0
Net Reserve (Recoverable)		140	140
Other structured finance [Member] | Financial Guarantee Insurance And Other 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		50	34
Salvage and Subrogation Recoverable, net		0	8
Net Reserve (Recoverable)		50	26
Structured Finance [Member] | Financial Guarantee Insurance And Other 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	528
Salvage and Subrogation Recoverable, net		123	134
Net Reserve (Recoverable)		383	394
Financial Guarantee [Member] | Financial Guarantee Insurance And Other 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		989	801
Salvage and Subrogation Recoverable, net		133	142
Net Reserve (Recoverable)		856	659
Other [Member] | Financial Guarantee Insurance And Other 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		8	13
Net Reserve (Recoverable)		(8)	(13)
United States [Member] | Public Finance [Member] | Financial Guarantee Insurance And Other 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		453	243
Salvage and Subrogation Recoverable, net		10	8
Net Reserve (Recoverable)		443	235
United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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		261	290
Salvage and Subrogation Recoverable, net		123	126
Net Reserve (Recoverable)		138	164
Non United States [Member] | Public Finance [Member] | Financial Guarantee Insurance And Other 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	30
Salvage and Subrogation Recoverable, net		0	0
Net Reserve (Recoverable)		30	30
First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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		252	283
Salvage and Subrogation Recoverable, net		52	48
Net Reserve (Recoverable)		200	235
Second Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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		9	7
Salvage and Subrogation Recoverable, net		71	78
Net Reserve (Recoverable)		(62)	(71)
Prime [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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 And Other 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		76	87
Salvage and Subrogation Recoverable, net		0	0
Net Reserve (Recoverable)		76	87
Option ARM [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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		22	28
Salvage and Subrogation Recoverable, net		40	40
Net Reserve (Recoverable)		(18)	(12)
Subprime [Member] | First Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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		152	166
Salvage and Subrogation Recoverable, net		12	8
Net Reserve (Recoverable)		140	158
Closed-end [Member] | Second Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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	4
Salvage and Subrogation Recoverable, net		36	39
Net Reserve (Recoverable)		(32)	(35)
HELOCs [Member] | Second Lien [Member] | United States [Member] | RMBS [Member] | Financial Guarantee Insurance And Other 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	3
Salvage and Subrogation Recoverable, net		35	39
Net Reserve (Recoverable)		$ (30)	$ (36)

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