Financial Guaranty Insurance Premiums - Gross Premium Receivable Net of Commissions on Assumed Business Roll Forward (Details) - USD ($) $ in Millions	6 Months Ended				12 Months Ended
	Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Non-financial guaranty line of business	$ 1
Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Beginning of period, December 31	729		$ 876		$ 876
Premiums receivable acquired in Radian Asset Acquisition on April 1, 2015	2		0
Gross premium written, net of commissions on assumed business	61		61
Gross premiums received, net of commissions on assumed business	(79)		(97)
Changes in the expected term	(9)		(13)
Accretion of discount, net of commissions on assumed business	10		12
Foreign exchange translation	(8)		9
Consolidation/deconsolidation of FG VIEs	(4)		1
Other adjustments	0		0
End of period, June 30	702	[1]	849	[1]	$ 729
Variable Interest Entity, Primary Beneficiary [Member]
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
End of period, June 30	$ 23		$ 18
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	50.00%				51.00%

[1] Excludes $23 million and $18 million as of June 30, 2015 and June 30, 2014, respectively, related to consolidated FG VIEs. Excludes $1 million related to non-financial guaranty line of business as of June 30, 2015.