Financial Guaranty Insurance Premiums - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Beginning of period, December 31	$ 876	[1]	$ 1,005	[1]	$ 1,003
Gross premium written, net of commissions on assumed business	171		145		211
Gross premiums received, net of commissions on assumed business	(230)		(259)		(294)
Changes in the expected term	(66)		(28)		44
Accretion of discount, net of commissions on assumed business	10		20		36
Foreign exchange translation	(31)		(1)		13
Consolidation/deconsolidation of FG VIEs	(1)		0		(5)
Other adjustments	0		(6)		(3)
End of period, December 31	729	[1]	876	[1]	1,005	[1]
Variable Interest Entity, Primary Beneficiary [Member]
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
End of period, December 31	$ 19		$ 21		$ 29
Foreign Currency Concentration Risk [Member] | Premiums Receivable [Member]
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Percentage of installment premiums denominated in currencies other than the U.S. dollar	51.00%		48.00%

[1] Excludes $19 million, $21 million and $29 million as of December 31, 2014 , 2013 and 2012, respectively, related to consolidated FG VIEs.