Financial Guaranty Insurance Losses - Reconciliation of Net Expected Loss to be Paid and Expensed (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014		Mar. 31, 2014		Dec. 31, 2013
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	$ 1,154	[1]	$ 1,169	[1]	$ 984	[1]	$ 982	[1]
Loss and LAE reserve, net of reinsurance	(710)	[2]	(721)	[2]
Other recoveries	7		13
Net expected loss to be expensed (present value)	315
Variable Interest Entity, Primary Beneficiary [Member]
Guarantor Obligations [Line Items]
Net expected loss to be expensed (present value)	86
Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Guarantor Obligations [Line Items]
Contra-paid, net	(93)	[3],[4]	(100)	[3],[4]
Financial Guarantee Insurance Product Line [Member]
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	989
Contra-paid, net	(93)
Salvage and subrogation recoverable, net of reinsurance	121
Loss and LAE reserve, net of reinsurance	(709)		(719)
Other recoveries	7
Net expected loss to be expensed (present value)	315	[5]
Financial Guarantee Insurance Product Line [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Guarantor Obligations [Line Items]
Loss and LAE reserve, net of reinsurance	78		80
Financial Guarantee Insurance Product Line [Member] | Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	1,111
Loss and LAE reserve, net of reinsurance	(787)		(799)
Financial Guarantee Insurance Product Line [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Guarantor Obligations [Line Items]
Net expected loss to be paid after recoveries for R&W	$ 122

[1] Includes expected LAE to be paid of $13 million as of March 31, 2015 and $16 million as of December 31, 2014.

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

[3] See Note 6, "Financial Guaranty Insurance Losses– Insurance Contracts' Loss Information" for an explanation of "contra-paid".

[4] Excludes $125 million and $125 million of deferred premium revenue, and $41 million and $42 million of contra-paid related to FG VIEs as of March 31, 2015 and December 31, 2014, respectively.

[5] Excludes $86 million as of March 31, 2015, related to consolidated FG VIEs.