Financial Guaranty Insurance Contracts (Details 10) (USD $)	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2010
Loss and LAE Reserve
Subtotal	$ 697,500,000	$ 601,600,000
Effect of consolidating FG VIEs	(74,800,000)	(49,500,000)
Total	622,700,000	552,100,000
Salvage and Subrogation Recoverable
Subtotal	551,400,000	995,200,000
Effect of consolidating FG VIEs	(236,800,000)	(92,200,000)
Total	314,600,000	903,000,000
Net
Subtotal	146,100,000	(393,600,000)
Effect of consolidating FG VIEs	162,000,000	42,700,000
Total	308,100,000	(350,900,000)
Loss and LAE reserves, gross	670,743,000	574,369,000
Reinsurance recoverable on unpaid losses	48,000,000	22,300,000
Ceded salvage and subrogation	45,600,000	129,400,000	97,200,000
Public finance | Financial Guaranty
Loss and LAE Reserve
Subtotal	56,500,000	81,600,000
Salvage and Subrogation Recoverable
Subtotal	64,300,000	34,400,000
Net
Subtotal	(7,800,000)	47,200,000
Total first lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	341,200,000	372,000,000
Salvage and Subrogation Recoverable
Subtotal	168,800,000	65,700,000
Net
Subtotal	172,400,000	306,300,000
U.S. RMBS | Financial Guaranty
Loss and LAE Reserve
Subtotal	400,000,000	386,800,000
Salvage and Subrogation Recoverable
Subtotal	481,300,000	959,400,000
Net
Subtotal	(81,300,000)	(572,600,000)
Prime first lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	1,800,000	1,200,000
Net
Subtotal	1,800,000	1,200,000
Alt-A first lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	70,900,000	39,200,000
Salvage and Subrogation Recoverable
Subtotal	47,700,000	2,600,000
Net
Subtotal	23,200,000	36,600,000
Option ARM | Financial Guaranty
Loss and LAE Reserve
Subtotal	167,000,000	223,300,000
Salvage and Subrogation Recoverable
Subtotal	121,100,000	63,000,000
Net
Subtotal	45,900,000	160,300,000
Subprime | Financial Guaranty
Loss and LAE Reserve
Subtotal	101,500,000	108,300,000
Salvage and Subrogation Recoverable
Subtotal		100,000
Net
Subtotal	101,500,000	108,200,000
CES | Financial Guaranty
Loss and LAE Reserve
Subtotal	9,300,000	7,700,000
Salvage and Subrogation Recoverable
Subtotal	114,100,000	50,300,000
Net
Subtotal	(104,800,000)	(42,600,000)
HELOCs | Financial Guaranty
Loss and LAE Reserve
Subtotal	49,500,000	7,100,000
Salvage and Subrogation Recoverable
Subtotal	198,400,000	843,400,000
Net
Subtotal	(148,900,000)	(836,300,000)
Second lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	58,800,000	14,800,000
Salvage and Subrogation Recoverable
Subtotal	312,500,000	893,700,000
Net
Subtotal	(253,700,000)	(878,900,000)
Other Structured finance. | Financial Guaranty
Loss and LAE Reserve
Subtotal	239,100,000	131,100,000
Salvage and Subrogation Recoverable
Subtotal	5,800,000	1,400,000
Net
Subtotal	233,300,000	129,700,000
Financial Guaranty
Loss and LAE Reserve
Subtotal	695,600,000	599,500,000
Total	620,800,000		457,900,000
Salvage and Subrogation Recoverable
Subtotal	551,400,000	995,200,000
Net
Subtotal	144,200,000	(395,700,000)
Effect of consolidating FG VIEs	162,000,000	42,700,000
Total	306,200,000	(353,000,000)
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