Financial Guaranty Insurance Contracts (Details 5) (USD $)	3 Months Ended
	Mar. 31, 2012 Payment	Dec. 31, 2011	Mar. 31, 2012 Financial Guaranty	Dec. 31, 2011 Financial Guaranty	Mar. 31, 2011 Financial Guaranty	Dec. 31, 2010 Financial Guaranty	Mar. 31, 2012 Financial Guaranty Total first lien	Dec. 31, 2011 Financial Guaranty Total first lien	Mar. 31, 2011 Financial Guaranty Total first lien	Dec. 31, 2010 Financial Guaranty Total first lien	Mar. 31, 2012 Financial Guaranty Second lien	Dec. 31, 2011 Financial Guaranty Second lien	Mar. 31, 2011 Financial Guaranty Second lien	Dec. 31, 2010 Financial Guaranty Second lien	Mar. 31, 2012 Financial Guaranty Subprime	Dec. 31, 2011 Financial Guaranty Subprime	Mar. 31, 2011 Financial Guaranty Subprime	Dec. 31, 2010 Financial Guaranty Subprime	Mar. 31, 2012 Other	Dec. 31, 2011 Other
Reconciliation of Expected Loss to be Paid and Net Expected Loss to be Expensed
Net expected loss to be paid			$ 752,400,000	$ 638,000,000	$ 32,200,000	$ 408,800,000	$ 344,800,000	$ 429,900,000	$ 662,500,000	$ 909,900,000	$ (132,200,000)	$ (110,700,000)	$ (869,600,000)	$ (749,100,000)	$ 150,400,000	$ 140,300,000	$ 167,500,000	$ 200,400,000	$ 1,900,000	$ 1,900,000
Less: net expected loss to be paid for FG VIEs			155,500,000	106,700,000
Total			907,900,000	744,700,000
Contra-paid, net			71,200,000	73,400,000
Salvage and subrogation recoverable	367,343,000	367,718,000	367,300,000
Ceded salvage and subrogation recoverable	(42,900,000)	(40,600,000)	(42,900,000)
Loss and LAE reserve	(801,600,000)	(609,700,000)	(951,300,000)
Reinsurance recoverable on unpaid losses	152,898,000	69,300,000	151,600,000
Total present value basis			503,800,000
Net expected loss to be expensed related to consolidated financial guaranty VIEs	$ 211,000,000
Maximum number of payments behind to be considered performing borrower	1