Financial Guaranty Insurance Premiums - Net Earned Premiums (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Financial Guarantee Insurance Premiums [Line Items]
Net earned premiums	$ 158	$ 144	$ 136	$ 132	$ 182	$ 159	$ 163	$ 248	$ 570		$ 752		$ 853
Consolidated Entity Excluding Consolidation of Variable Interest Entities (VIE) [Member]
Financial Guarantee Insurance Premiums [Line Items]
Scheduled net earned premiums									415		470		581
Acceleration of net earned premiums									136		263		249
Accretion of discount on net premiums receivable									16		17		22
Financial guaranty insurance net earned premiums									567		750		852
Other									3		2		1
Net earned premiums									570	[1]	752	[1]	853	[1]
Variable Interest Entity, Primary Beneficiary [Member]
Financial Guarantee Insurance Premiums [Line Items]
Net earned premiums									$ 32		$ 60		$ 153

[1] Excludes $32 million, $60 million and $153 million for the year ended December 31, 2014, 2013 and 2012, respectively, related to consolidated FG VIEs.