Financial Guaranty Insurance Premiums (Gross Premium Receivable Net of Ceding Commissions Roll Forward) (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Gross Premium Receivable Net of Ceding Commissions [Roll Forward]
Balance beginning of period, December 31	$ 1,005		$ 1,003
Premium written, net	17		56
Premium payments received, net	(53)		(86)
Changes in the expected term of financial guaranty insurance contracts	1		33
Accretion of discount on net premiums receivable	(9)		(6)
Foreign exchange translation	(23)		12
Consolidation of FG VIEs	0		(5)
Balance end of period, December 31	956	[1]	1,019	[1]
Gross premium receivable, net of ceding commissions of consolidated FG VIEs	$ 28		$ 33
Percentage of installment premiums denominated in foreign currencies	46.00%				47.00%

[1] )Excludes $28 million and $33 million as of March 31, 2013 and March 31, 2012, respectively, related to consolidated FG VIEs.