Financial Guaranty Insurance Losses (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	$ 638		$ 607
Subtotal, Salvage and Subrogation Recoverable, net	337		627
Subtotal, Net	301		(20)
Effect of consolidating FG VIEs, Loss and LAE Reserve, net	(96)		(64)
Effect of consolidating FG VIEs, Salvage and Subrogation Recoverable, net	(88)		(217)
Effect of consolidating FG VIEs, Net	(8)		153
Total, Loss and LAE Reserve, net	542	[1]	543	[1]
Total, Salvage and subrogation recoverable payable, net	249	[1]	410	[1]
Total, Net	293	[1]	133	[1]
Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	636		605
Subtotal, Salvage and Subrogation Recoverable, net	332		622
Subtotal, Net	304		(17)
Total, Net	273		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
Prime first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	3		3
Subtotal, Salvage and Subrogation Recoverable, net	0		0
Subtotal, Net	3		3
Alt-A first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	105		93
Subtotal, Salvage and Subrogation Recoverable, net	52		0
Subtotal, Net	53		93
Option ARM | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	33		52
Subtotal, Salvage and Subrogation Recoverable, net	38		216
Subtotal, Net	(5)		(164)
First mortgage, subprime | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	131		82
Subtotal, Salvage and Subrogation Recoverable, net	1		0
Subtotal, Net	130		82
Total first lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	272		230
Subtotal, Salvage and Subrogation Recoverable, net	91		216
Subtotal, Net	181		14
Close ended second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	5		5
Subtotal, Salvage and Subrogation Recoverable, net	47		72
Subtotal, Net	(42)		(67)
HELOCs | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	6		37
Subtotal, Salvage and Subrogation Recoverable, net	141		196
Subtotal, Net	(135)		(159)
Second lien | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	11		42
Subtotal, Salvage and Subrogation Recoverable, net	188		268
Subtotal, Net	(177)		(226)
U.S. RMBS | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	283		272
Subtotal, Salvage and Subrogation Recoverable, net	279		484
Subtotal, Net	4		(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	143		197
Subtotal, Salvage and Subrogation Recoverable, net	5		4
Subtotal, Net	138		193
US Public Finance | Financial guaranty
Guarantor Obligations [Line Items]
Subtotal, Loss and LAE Reserve, net	177		104
Subtotal, Salvage and Subrogation Recoverable, net	48		134
Subtotal, Net	129		(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.