Financial Guaranty Insurance Contracts (Details 11) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Loss and LAE Reserve
Subtotal	$ 603		$ 672
Effect of consolidating FG VIEs	(65)		(62)
Subtotal	538	[1]	610	[1]
Salvage and Subrogation Recoverable
Subtotal	587		585
Effect of consolidating FG VIEs	(204)		(258)
Subtotal	383	[1]	327	[1]
Net
Subtotal	16		87
Effect of consolidating FG VIEs	139		196
Total	155	[1]	283	[1]
Financial Guaranty
Loss and LAE Reserve
Subtotal	601		670
Salvage and Subrogation Recoverable
Subtotal	581		585
Net
Subtotal	20		85
Total	129		281
Financial Guaranty | U.S. RMBS
Loss and LAE Reserve
Subtotal	291		336
Salvage and Subrogation Recoverable
Subtotal	473		509
Net
Subtotal	(182)		(173)
Financial Guaranty | Total first lien
Loss and LAE Reserve
Subtotal	239		264
Salvage and Subrogation Recoverable
Subtotal	212		196
Net
Subtotal	27		68
Financial Guaranty | Prime first lien
Loss and LAE Reserve
Subtotal	3		1
Salvage and Subrogation Recoverable
Subtotal	0		0
Net
Subtotal	3		1
Financial Guaranty | Alt-A first lien
Loss and LAE Reserve
Subtotal	86		70
Salvage and Subrogation Recoverable
Subtotal	0		55
Net
Subtotal	86		15
Financial Guaranty | First Mortgage Option Adjustable Rate Mortgage [Member]
Loss and LAE Reserve
Subtotal	71		142
Salvage and Subrogation Recoverable
Subtotal	212		141
Net
Subtotal	(141)		1
Financial Guaranty | Subprime
Loss and LAE Reserve
Subtotal	79		51
Salvage and Subrogation Recoverable
Subtotal	0		0
Net
Subtotal	79		51
Financial Guaranty | Second lien
Loss and LAE Reserve
Subtotal	52		72
Salvage and Subrogation Recoverable
Subtotal	261		313
Net
Subtotal	(209)		(241)
Financial Guaranty | CES
Loss and LAE Reserve
Subtotal	11		11
Salvage and Subrogation Recoverable
Subtotal	67		136
Net
Subtotal	(56)		(125)
Financial Guaranty | HELOCs
Loss and LAE Reserve
Subtotal	41		61
Salvage and Subrogation Recoverable
Subtotal	194		177
Net
Subtotal	(153)		(116)
Financial Guaranty | TruPS [Member]
Loss and LAE Reserve
Subtotal	7		11
Salvage and Subrogation Recoverable
Subtotal	0		0
Net
Subtotal	7		11
Financial Guaranty | Structured finance
Loss and LAE Reserve
Subtotal	194		223
Salvage and Subrogation Recoverable
Subtotal	5		6
Net
Subtotal	189		217
Financial Guaranty | US Public Finance [Member]
Loss and LAE Reserve
Subtotal	80		62
Salvage and Subrogation Recoverable
Subtotal	103		70
Net
Subtotal	(23)		(8)
Financial Guaranty | Public finance Non-U.S.
Loss and LAE Reserve
Subtotal	29		38
Salvage and Subrogation Recoverable
Subtotal	0		0
Net
Subtotal	29		38
Other
Loss and LAE Reserve
Subtotal	2		2
Salvage and Subrogation Recoverable
Subtotal	6		0
Net
Subtotal	(4)		2
Total	$ (4)		$ 2

[1] See “Components of Net Reserves (Salvage)” table for loss and LAE reserve and salvage and subrogation recoverable components.