Financial Guaranty Insurance Acquisition Costs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Beginning of period	$ 124	$ 116	$ 132
Commissions on assumed and ceded business	7	9	(13)
Premium taxes	3	4	4
Compensation and other acquisition costs	10	8	10
Total costs deferred	20	21	1
Amortization of deferred acquisition costs	(23)	(13)	(17)
End of period	$ 121	$ 124	$ 116