Financial Guaranty Insurance Losses (Reconciliation of Net Expected Loss to be Paid and Expensed) (Details 3) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Guarantor Obligations [Line Items]
Less: net expected loss to be paid for FG VIEs	$ (138)
Salvage and subrogation recoverable payable, net	493	[1]	410	[1]
Ceded salvage and subrogation recoverable	(50)	[2]	(46)	[2]
Reinsurance recoverable on unpaid losses	56		58
Net expected loss to be expensed related to consolidated financial guaranty VIEs	130
Consolidated Entity Excluding Variable Interest Entities (VIE)
Guarantor Obligations [Line Items]
Contra-paid, net	92
Other recoveries	27	[3]	30	[3]
Salvage and subrogation recoverable payable, net	488
Loss and LAE reserve	(474)
Reinsurance recoverable on unpaid losses	27	[3]
Financial Guarantee [Member]
Guarantor Obligations [Line Items]
Net expected loss to be paid	172
Total	310
Financial guaranty
Guarantor Obligations [Line Items]
Contra-paid, net	92	[4]	124	[4]
Total present value basis	443	[5],[6]
Below investment grade (BIG) | Financial Guarantee [Member]
Guarantor Obligations [Line Items]
Net expected loss to be paid			(355)
Below investment grade (BIG) | Financial guaranty
Guarantor Obligations [Line Items]
Net expected loss to be paid	(172)
Less: net expected loss to be paid for FG VIEs	(138)		(96)
Total	$ 310		$ 451

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

[2] Recorded as a component of reinsurance balances payable.

[3] R&W recoveries recorded in other assets on the consolidated balance sheet.

[4] (1)Excludes $244 million and $262 million of deferred premium revenue, and $72 million and $98 million of contra-paid related to FG VIEs as of March 31, 2013 and December 31, 2012, respectively.

[5] Excludes $130 million as of March 31, 2013, related to consolidated FG VIEs.

[6] Consolidation of FG VIEs resulted in reductions of $130 million in net expected loss to be expensed.