Financial Guaranty Insurance Contracts (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Net Earned Premiums
Net earned premiums	$ 193,677,000	$ 253,977,000
Net earned premium related to consolidated FG VIEs	(17,000,000)	(19,100,000)
Gross premium receivable, net of ceding commissions payable:
Balance beginning of period	1,002,852,000	1,167,600,000
Premium written, net	56,300,000	48,000,000
Premium payments received, net	(86,100,000)	(72,800,000)
Adjustments to the premium receivable:
Changes in the expected term of financial guaranty insurance contracts	32,700,000	(51,100,000)
Foreign exchange translation	12,200,000	15,900,000
Consolidation of FG VIEs	(5,400,000)
Other adjustments		1,200,000
Balance end of period	1,018,672,000	1,118,000,000
Gross premium receivable, net of ceding commissions of consolidated FG VIEs	32,600,000	19,800,000
Percentage of installment premium receivables denominated in currencies other than the U.S. dollar	48.00%	45.00%	47.00%
Gross premium collections expected:
Cash collections on FG VIEs	38,900,000
Financial Guaranty
Net Earned Premiums
Scheduled net earned premiums	152,000,000	214,900,000
Acceleration of premium earnings	36,600,000	29,600,000
Accretion of discount on net premiums receivable	4,700,000	9,000,000
Total net earned premiums	193,300,000	253,500,000
Adjustments to the premium receivable:
Accretion of discount	4,700,000	9,000,000
Gross premium collections expected:
2012 (April 1 - June 30)	56,600,000
2012 (July 1 - September 30)	30,800,000
2012 (October 1 - December 31)	44,600,000
2013	109,500,000
2014	95,900,000
2015	85,700,000
2016	79,800,000
2017-2021	315,900,000
2022-2026	214,600,000
2027-2031	158,700,000
After 2031	194,400,000
Total	1,386,500,000
Other
Net Earned Premiums
Net earned premiums	$ 400,000	$ 500,000