Financial Guaranty Insurance Contracts (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Gross
Total	$ 5,962,799,000	$ 6,972,894,000	$ 8,268,000,000
Ceded
Total	708,872,000	821,819,000
Net
Total	5,253,900,000	6,151,100,000
Total net unearned premium reserve related to FG VIE	274,200,000	193,200,000
Net
Reduction in future scheduled amortization of deferred premium revenue due to consolidating FG VIEs	407,200,000
Reduction in net present value of expected loss due to consolidating FG VIEs	222,700,000
Financial Guaranty
Gross
Deferred premium revenue	6,046,300,000	7,108,200,000
Contra-paid	(92,200,000)	(146,100,000)
Total	5,954,100,000	6,962,100,000
Ceded
Deferred premium revenue	727,400,000	846,200,000
Contra-paid	(18,800,000)	(24,800,000)
Total	708,600,000	821,400,000
Net
Deferred premium revenue	5,318,900,000	6,262,000,000
Contra-paid	(73,400,000)	(121,300,000)
Total	5,245,500,000	6,140,700,000
Scheduled Net Earned Premium
2012 (January 1 - March 31)	153,500,000
2012 (April 1 - June 30)	147,500,000
2012 (July 1 - September 30)	140,500,000
2012 (October 1 - December 31)	134,500,000
Subtotal 2012	576,000,000
2013	485,800,000
2014	426,500,000
2015	378,400,000
2016	343,100,000
2017-2021	1,297,700,000
2022-2026	811,800,000
2027-2031	492,500,000
After 2031	507,100,000
Total present value basis	5,318,900,000
Discount	296,000,000
Total future value	5,614,900,000
Net Expected Loss to be Expensed
2012 (January 1 - March 31)	32,100,000
2012 (April 1 - June 30)	27,500,000
2012 (July 1 - September 30)	24,000,000
2012 (October 1 - December 31)	20,900,000
Subtotal 2012	104,500,000
2013	61,000,000
2014	44,000,000
2015	34,900,000
2016	30,900,000
2017-2021	135,300,000
2022-2026	68,100,000
2027-2031	34,400,000
After 2031	24,300,000
Total present value basis	537,400,000	833,900,000
Discount	276,100,000
Total future value	813,500,000
Net
2012 (January 1 - March 31)	121,400,000
2012 (April 1 - June 30)	120,000,000
2012 (July 1 - September 30)	116,500,000
2012 (October 1 - December 31)	113,600,000
Subtotal 2012	471,500,000
2013	424,800,000
2014	382,500,000
2015	343,500,000
2016	312,200,000
2017-2021	1,162,400,000
2022-2026	743,700,000
2027-2031	458,100,000
After 2031	482,800,000
Total present value basis	4,781,500,000
Discount	19,900,000
Total future value	4,801,400,000
Other
Gross
Total	8,700,000	10,800,000
Ceded
Total	300,000	400,000
Net
Total	$ 8,400,000	$ 10,400,000