Financial Guaranty Insurance - Loss and LAE Reported on the Statements of Operations (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE	$ 106	$ 112	$ 188	$ 18	$ 72	$ (44)	$ 57	$ 41	$ 424	$ 126	$ 154
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									452	156	175
Variable Interest Entity, Primary Beneficiary [Member]
Liability for Claims and Claims Adjustment Expense Including Salvage and Subrogation Recoverable [Line Items]
Loss and LAE									(28)	(30)	(21)
Residential Mortgage-Backed Securities (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									54	(129)	(4)
XXX 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									16	85	(44)
Trust preferred securities (TruPS) [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									(1)	(1)	(1)
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									(9)	17	10
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									(1)	(7)	0
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									59	(35)	(39)
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									393	191	214
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									392	192	198
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									1	(1)	16
First Lien [Member] | Residential Mortgage-Backed Securities (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									(6)	(96)	31
Second Lien [Member] | Residential Mortgage-Backed Securities (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									60	(33)	(35)
Financing Receivable, Prime [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (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									(1)	(1)	1
Alt-A [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (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									(23)	(66)	(2)
Option ARM [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (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									(15)	(37)	(48)
Subprime [Member] | First Lien [Member] | Residential Mortgage-Backed Securities (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									$ 33	$ 8	$ 80