Financial Guaranty Insurance Contracts (Details 10) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Loss and LAE Reserve
Subtotal	$ 556,900,000	$ 601,600,000
Effect of consolidating FG VIEs	(64,800,000)	(49,500,000)
Total	492,100,000	552,100,000
Salvage and Subrogation Recoverable
Subtotal	464,800,000	995,200,000
Effect of consolidating FG VIEs	(192,900,000)	(92,200,000)
Total	271,900,000	903,000,000
Net
Subtotal	92,100,000	(393,600,000)
Effect of consolidating FG VIEs	(128,100,000)	(42,700,000)
Total	220,200,000	(350,900,000)
Loss and LAE reserves, gross	518,145,000	574,369,000
Reinsurance recoverable on unpaid losses	26,625,000	22,255,000
Ceded salvage and subrogation	35,200,000	129,400,000
Public finance | Financial Guaranty
Loss and LAE Reserve
Subtotal	64,000,000	81,600,000
Salvage and Subrogation Recoverable
Subtotal	37,900,000	34,400,000
Net
Subtotal	26,100,000	47,200,000
Total first lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	272,500,000	372,000,000
Salvage and Subrogation Recoverable
Subtotal	111,900,000	65,700,000
Net
Subtotal	160,600,000	306,300,000
U.S. RMBS | Financial Guaranty
Loss and LAE Reserve
Subtotal	341,600,000	386,800,000
Salvage and Subrogation Recoverable
Subtotal	424,400,000	959,400,000
Net
Subtotal	(82,800,000)	(572,600,000)
Prime first lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	2,500,000	1,200,000
Net
Subtotal	2,500,000	1,200,000
Alt-A first lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	46,500,000	39,200,000
Salvage and Subrogation Recoverable
Subtotal	5,500,000	2,600,000
Net
Subtotal	41,000,000	36,600,000
Option ARM | Financial Guaranty
Loss and LAE Reserve
Subtotal	136,100,000	223,300,000
Salvage and Subrogation Recoverable
Subtotal	106,300,000	63,000,000
Net
Subtotal	29,800,000	160,300,000
Subprime | Financial Guaranty
Loss and LAE Reserve
Subtotal	87,400,000	108,300,000
Salvage and Subrogation Recoverable
Subtotal	100,000	100,000
Net
Subtotal	87,300,000	108,200,000
CES | Financial Guaranty
Loss and LAE Reserve
Subtotal	9,300,000	7,700,000
Salvage and Subrogation Recoverable
Subtotal	129,600,000	50,300,000
Net
Subtotal	(120,300,000)	(42,600,000)
HELOCs | Financial Guaranty
Loss and LAE Reserve
Subtotal	59,800,000	7,100,000
Salvage and Subrogation Recoverable
Subtotal	182,900,000	843,400,000
Net
Subtotal	(123,100,000)	(836,300,000)
Second lien | Financial Guaranty
Loss and LAE Reserve
Subtotal	69,100,000	14,800,000
Salvage and Subrogation Recoverable
Subtotal	312,500,000	893,700,000
Net
Subtotal	(243,400,000)	(878,900,000)
Other Structured finance. | Financial Guaranty
Loss and LAE Reserve
Subtotal	149,200,000	131,100,000
Salvage and Subrogation Recoverable
Subtotal	2,500,000	1,400,000
Net
Subtotal	146,700,000	129,700,000
Financial Guaranty
Loss and LAE Reserve
Subtotal	554,800,000	599,500,000
Total	490,000,000	550,000,000
Salvage and Subrogation Recoverable
Subtotal	464,800,000	995,200,000
Net
Subtotal	90,000,000	(395,700,000)
Effect of consolidating FG VIEs	(128,100,000)	42,700,000
Total	218,100,000	(353,000,000)
Ceded salvage and subrogation	35,200,000	129,400,000
Other
Loss and LAE Reserve
Subtotal	2,100,000	2,100,000
Total	(2,100,000)	(2,100,000)
Net
Subtotal	2,100,000	2,100,000
Total	$ 2,100,000	$ 2,100,000