Financial Guaranty Insurance Premiums (Net Deferred Premium Revenue Roll Forward) (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Net Deferred Premium Revenue Roll Forward [Roll Forward]
Balance beginning of period	$ 4,770	[1]	$ 5,327
Premium written, net	14		13
Net premium earned, excluding accretion	(241)		(189)
Commutations and changes in expected premiums	1		130
Foreign exchange translation	(4)		3
Consolidation of FG VIEs	(1)		(5)
Balance, end of period	$ 4,539	[1]	$ 5,279

[1] (1)Excludes $244 million and $262 million of deferred premium revenue, and $72 million and $98 million of contra-paid related to FG VIEs as of March 31, 2013 and December 31, 2012, respectively.