Financial Guaranty Insurance - Loss and LAE Reported on the Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	$ 90	$ 18
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	97	23
Variable Interest Entity, Primary Beneficiary [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	(7)	(5)
RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	11	7
Triple-X Life Insurance Transaction [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	3	6
Student Loan [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	(14)	(6)
Other structured finance [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	0	(2)
Structured Finance [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	0	5
Public Finance [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	97	18
Public Finance [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	97	13
Public Finance [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | Non United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	0	5
First Lien [Member] | RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	(2)	(3)
Second Lien [Member] | RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	13	10
Financing Receivable, Prime [Member] | First Lien [Member] | RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	0	0
Alt-A [Member] | First Lien [Member] | RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	8	(2)
Option ARM [Member] | First Lien [Member] | RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	(14)	(1)
Subprime [Member] | First Lien [Member] | RMBS [Member] | Financial Guarantee Insurance And Other Product Line [Member] | Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | United States [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	$ 4	$ 0