Consolidation of Variable Interest Entities (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011 Entity	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011 Entity	Dec. 31, 2010 Entity	Dec. 31, 2009
Consolidated VIEs
Number of additional VIEs required to be consolidated	8								8
Net loss on consolidation									$ (95,300,000)
Number of VIEs whose debt was fully paid down									4
Consolidated VIEs
Number of VIEs									33	29
Assets	2,819,077,000				3,657,481,000				2,819,077,000	3,657,481,000	1,925,300,000
Liabilities	3,458,400,000				4,368,100,000				3,458,400,000	4,368,100,000
Total unpaid principal balance for the VIEs' assets that were over 90 days or more past due	900,700,000								900,700,000
Change in the instrument specific credit risk of the VIEs' assets									600,400,000
Difference between the aggregate unpaid principal and aggregate fair value of the VIEs' liabilities	2,710,900,000								2,710,900,000
Gross par outstanding for FG VIEs liabilities with recourse	3,796,400,000				3,630,500,000				3,796,400,000	3,630,500,000
Contractual Maturity
2013	15,700,000								15,700,000
2014	138,900,000								138,900,000
Thereafter	3,641,800,000								3,641,800,000
Total	3,796,400,000				3,630,500,000				3,796,400,000	3,630,500,000
Net earned premiums									(74,700,000)	(47,600,000)
Net investment income									(8,300,000)
Net realized investment gains (losses)									11,900,000
Net change in fair value of financial guaranty variable interest entities:
Net change in fair value of FG VIEs	21,900,000	(99,200,000)	(174,300,000)	119,600,000	(408,600,000)	171,300,000	(27,400,000)	(8,900,000)	(131,984,000)	(273,652,000)	(1,156,000)
Loss and LAE									92,700,000	65,900,000
Total pre-tax effect on net income									(110,400,000)	(255,300,000)	(1,200,000)
Less: tax provision (benefit)									(38,700,000)	(89,400,000)
Total effect on net income									(71,700,000)	(165,900,000)	(1,200,000)
Total (decrease) increase on shareholders' equity									(405,200,000)	(371,400,000)
HELOCs
Consolidated VIEs
Number of VIEs									8	8
Assets	616,000,000				857,100,000				616,000,000	857,100,000
Liabilities	951,000,000				1,126,100,000				951,000,000	1,126,100,000
Alt-A first lien
Consolidated VIEs
Number of VIEs									3
Assets	146,600,000								146,600,000
Liabilities	134,800,000								134,800,000
Option ARM
Consolidated VIEs
Number of VIEs									2	2
Assets	524,400,000				626,600,000				524,400,000	626,600,000
Liabilities	719,300,000				909,400,000				719,300,000	909,400,000
Subprime
Consolidated VIEs
Number of VIEs									5	5
Assets	414,500,000				528,700,000				414,500,000	528,700,000
Liabilities	500,400,000				616,500,000				500,400,000	616,500,000
Closed end second lien
Consolidated VIEs
Number of VIEs									10	5
Assets	600,200,000				747,400,000				600,200,000	747,400,000
Liabilities	635,500,000				818,400,000				635,500,000	818,400,000
Automobile loans
Consolidated VIEs
Number of VIEs									4	7
Assets	227,600,000				486,800,000				227,600,000	486,800,000
Liabilities	227,600,000				486,800,000				227,600,000	486,800,000
Life insurance
Consolidated VIEs
Number of VIEs									1	1
Assets	289,800,000				304,800,000				289,800,000	304,800,000
Liabilities	289,800,000				304,800,000				289,800,000	304,800,000
Credit card loans
Consolidated VIEs
Number of VIEs										1
Assets					106,100,000					106,100,000
Liabilities					$ 106,100,000					$ 106,100,000