Financial Guaranty Insurance Premiums (Net Earned Premiums) (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Financial Guaranty Insurance Premiums [Line Items]
Accretion of discount on net premiums receivable	$ (9)		$ (6)
Net earned premiums	248	[1]	194	[1]
Net earned premiums	18		17
Financial guaranty
Financial Guaranty Insurance Premiums [Line Items]
Scheduled net earned premiums	128		152
Acceleration of premium earnings	113		37
Accretion of discount on net premiums receivable	7		5
Total financial guaranty insurance	248		194
Other
Financial Guaranty Insurance Premiums [Line Items]
Net earned premiums	$ 0		$ 0

[1] Excludes $18 million and $17 million for First Quarter 2013 and 2012, respectively, related to consolidated FG VIEs.