Financial Guaranty Insurance Premiums (Selected Information for Policies Paid in Installments) (Details 7) (USD $) In Millions, unless otherwise specified								12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009	Dec. 31, 2012 Policies Paid in Installments	Dec. 31, 2011 Policies Paid in Installments
Financial Guaranty Insurance Premiums [Line Items]
Premiums receivable, net of ceding commissions payable	$ 1,005	[1]	$ 1,003	[1]	$ 1,168	[1]	$ 1,418	$ 1,005	$ 1,003
Deferred premium revenue, gross	$ 5,356		$ 6,055					$ 1,908	$ 2,193
Weighted-average risk-free rate used to discount premiums (as a percent)								3.50%	3.40%
Weighted-average period of premiums receivable (in years)								9 years 7 months 6 days	9 years 9 months 18 days

[1] 2)Excludes $29 million, $28 million and $23 million as of December 31, 2012 , 2011 and 2010, respectively, related to consolidated FG VIEs.