Financial Guaranty Insurance Contracts (Details 11) (USD $)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Loss and LAE Reserve
Subtotal	$ 671,300,000	$ 601,600,000
Effect of consolidating FG VIEs	(61,600,000)	(49,500,000)
Total	609,700,000	552,100,000
Salvage and Subrogation Recoverable
Subtotal	585,200,000	995,200,000
Effect of consolidating FG VIEs	(258,100,000)	(92,200,000)
Total	327,100,000	903,000,000
Net
Subtotal	86,100,000	(393,600,000)
Effect of consolidating FG VIEs	(196,500,000)	42,700,000
Total	282,600,000	(350,900,000)
Loss and LAE reserves, gross	679,011,000	574,369,000	306,400,000
Reinsurance recoverable on unpaid losses	69,300,000	22,255,000
Salvage and subrogation recoverable	367,718,000	1,032,369,000
Ceded salvage and subrogation recoverable	40,600,000	129,400,000
Financial Guaranty
Loss and LAE Reserve
Subtotal	669,400,000	599,500,000
Total	676,900,000	570,800,000
Salvage and Subrogation Recoverable
Subtotal	585,200,000	995,200,000
Net
Subtotal	84,200,000	(395,700,000)
Effect of consolidating FG VIEs	196,500,000	42,700,000
Total	280,700,000	(353,000,000)
Reinsurance recoverable on unpaid losses	69,100,000	20,800,000
Salvage and subrogation recoverable	367,718,000	1,032,369,000
Ceded salvage and subrogation recoverable	40,600,000	129,400,000
Financial Guaranty | U.S. RMBS
Loss and LAE Reserve
Subtotal	336,400,000	386,800,000
Salvage and Subrogation Recoverable
Subtotal	509,400,000	959,400,000
Net
Subtotal	(173,000,000)	(572,600,000)
Financial Guaranty | Total first lien
Loss and LAE Reserve
Subtotal	264,100,000	372,000,000
Salvage and Subrogation Recoverable
Subtotal	196,000,000	65,700,000
Net
Subtotal	68,100,000	306,300,000
Financial Guaranty | Prime first lien
Loss and LAE Reserve
Subtotal	1,200,000	1,200,000
Net
Subtotal	1,200,000	1,200,000
Financial Guaranty | Alt-A first lien
Loss and LAE Reserve
Subtotal	69,800,000	39,200,000
Salvage and Subrogation Recoverable
Subtotal	55,400,000	2,600,000
Net
Subtotal	14,400,000	36,600,000
Financial Guaranty | Option ARM
Loss and LAE Reserve
Subtotal	141,700,000	223,300,000
Salvage and Subrogation Recoverable
Subtotal	140,300,000	63,000,000
Net
Subtotal	1,400,000	160,300,000
Financial Guaranty | Subprime
Loss and LAE Reserve
Subtotal	51,400,000	108,300,000
Salvage and Subrogation Recoverable
Subtotal	300,000	100,000
Net
Subtotal	51,100,000	108,200,000
Financial Guaranty | Second lien
Loss and LAE Reserve
Subtotal	72,300,000	14,800,000
Salvage and Subrogation Recoverable
Subtotal	313,400,000	893,700,000
Net
Subtotal	(241,100,000)	(878,900,000)
Financial Guaranty | CES
Loss and LAE Reserve
Subtotal	11,200,000	7,700,000
Salvage and Subrogation Recoverable
Subtotal	136,200,000	50,300,000
Net
Subtotal	(125,000,000)	(42,600,000)
Financial Guaranty | HELOCs
Loss and LAE Reserve
Subtotal	61,100,000	7,100,000
Salvage and Subrogation Recoverable
Subtotal	177,200,000	843,400,000
Net
Subtotal	(116,100,000)	(836,300,000)
Financial Guaranty | Structured Finance
Loss and LAE Reserve
Subtotal	233,000,000	131,100,000
Salvage and Subrogation Recoverable
Subtotal	5,900,000	1,400,000
Net
Subtotal	227,100,000	129,700,000
Financial Guaranty | Public finance
Loss and LAE Reserve
Subtotal	100,000,000	81,600,000
Salvage and Subrogation Recoverable
Subtotal	69,900,000	34,400,000
Net
Subtotal	30,100,000	47,200,000
Other
Loss and LAE Reserve
Subtotal	1,900,000	2,100,000
Net
Subtotal	1,900,000	2,100,000
Total	$ 1,900,000	$ 2,100,000