Financial Guaranty Insurance Contracts (Details 2) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011		Dec. 31, 2011
Net Earned Premiums
Accretion of discount on net premiums receivable					$ (13,400,000)		$ (16,400,000)
Net earned premiums	219,299,000		230,068,000		412,976,000		484,045,000
Net earned premium related to consolidated FG VIEs	15,500,000	[1]	18,300,000	[1]	32,500,000	[1]	37,400,000	[1]
Gross premium receivable, net of ceding commissions payable:
Balance beginning of period					1,002,852,000		1,167,600,000
Premium written, net					102,700,000		102,900,000
Premium payments received, net					(166,500,000)		(151,700,000)
Adjustments to the premium receivable:
Changes in the expected term of financial guaranty insurance contracts					18,800,000		(91,100,000)
Accretion of discount					13,400,000		16,400,000
Foreign exchange translation					(500,000)		22,800,000
Consolidation of FG VIEs					(5,400,000)		(9,900,000)
Other adjustments					(1,300,000)		2,500,000
Balance end of period	964,063,000		1,059,500,000	[2]	964,063,000		1,059,500,000	[2]
Gross premium receivable, net of ceding commissions of consolidated FG VIEs	31,700,000		31,700,000		31,700,000		31,700,000
Percentage of installment premium receivables denominated in currencies other than the U.S. dollar	49.00%		51.00%		49.00%		51.00%		47.00%
Gross premium collections expected:
Cash collections on FG VIEs	37,800,000				37,800,000
Financial Guaranty
Net Earned Premiums
Scheduled net earned premiums	144,700,000		202,700,000		296,700,000		417,600,000
Acceleration of premium earnings	68,200,000		21,000,000		104,800,000		50,600,000
Accretion of discount on net premiums receivable	6,300,000		5,800,000		11,000,000		14,800,000
Total financial guaranty	219,200,000		229,500,000		412,500,000		483,000,000
Adjustments to the premium receivable:
Accretion of discount	(6,300,000)		(5,800,000)		(11,000,000)		(14,800,000)
Gross premium collections expected:
2012 (July 1 - September 30)	48,400,000				48,400,000
2012 (October 1 - December 31)	50,000,000				50,000,000
2013	106,600,000				106,600,000
2014	93,300,000				93,300,000
2015	83,300,000				83,300,000
2016	77,300,000				77,300,000
2017-2021	305,600,000				305,600,000
2022-2026	206,600,000				206,600,000
2027-2031	152,200,000				152,200,000
After 2031	187,600,000				187,600,000
Total	1,310,900,000	[3]			1,310,900,000	[3]
Other
Net Earned Premiums
Net earned premiums	$ 100,000		$ 500,000		$ 500,000		$ 1,000,000

[1] Includes the effect of eliminating insurance balances related to the financial guaranty insurance contracts.

[2] Excludes $31.7 million and $31.7 million as of June 30, 2012 and 2011, respectively, related to consolidated FG VIEs.

[3] Excludes expected cash collections on FG VIEs of $37.8 million.