Financial Guaranty Insurance Losses (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	$ 591		$ 607
Subtotal, Salvage and Subrogation Recoverable, net	397		627
Subtotal, Net	194		(20)
Effect of consolidating FG VIEs, Loss and LAE Reserve, net	(87)		(64)
Effect of consolidating FG VIEs, Salvage and Subrogation Recoverable, net	(103)		(217)
Effect of consolidating FG VIEs, Net	16		153
Total, Loss and LAE Reserve, net	(504)	[1]	(543)	[1]
Total, Salvage and subrogation recoverable payable, net	294	[1]	410	[1]
Total, Net	210	[1]	133	[1]
Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	589		605
Subtotal, Salvage and Subrogation Recoverable, net	392		622
Subtotal, Net	197		(17)
Total, Net	189		106
Other
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	2		2
Subtotal, Salvage and Subrogation Recoverable, net	5		5
Subtotal, Net	(3)		(3)
Total, Net	3		3
Prime first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	2		3
Subtotal, Salvage and Subrogation Recoverable, net	0		0
Subtotal, Net	2		3
Alt-A first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	78		93
Subtotal, Salvage and Subrogation Recoverable, net	2		0
Subtotal, Net	76		93
First mortgage, option adjustable rate mortgage | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	30		52
Subtotal, Salvage and Subrogation Recoverable, net	60		216
Subtotal, Net	(30)		(164)
First mortgage, subprime | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	108		82
Subtotal, Salvage and Subrogation Recoverable, net	2		0
Subtotal, Net	106		82
Total first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	218		230
Subtotal, Salvage and Subrogation Recoverable, net	64		216
Subtotal, Net	154		14
Close ended second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	4		5
Subtotal, Salvage and Subrogation Recoverable, net	49		72
Subtotal, Net	(45)		(67)
HELOCs | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	22		37
Subtotal, Salvage and Subrogation Recoverable, net	147		196
Subtotal, Net	(125)		(159)
Second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	26		42
Subtotal, Salvage and Subrogation Recoverable, net	196		268
Subtotal, Net	(170)		(226)
U.S. RMBS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	244		272
Subtotal, Salvage and Subrogation Recoverable, net	260		484
Subtotal, Net	(16)		(212)
TruPS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	2		1
Subtotal, Salvage and Subrogation Recoverable, net	0		0
Subtotal, Net	2		1
Structured finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	170		197
Subtotal, Salvage and Subrogation Recoverable, net	5		4
Subtotal, Net	165		193
US Public Finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	142		104
Subtotal, Salvage and Subrogation Recoverable, net	127		134
Subtotal, Net	15		(30)
Public finance Non-U.S. | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	31		31
Subtotal, Salvage and Subrogation Recoverable, net	0		0
Subtotal, Net	$ 31		$ 31

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