Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred tax assets:
Unrealized losses on credit derivative financial instruments, net	$ 266,900,000	$ 401,600,000
Unearned premium reserves, net	424,200,000	641,600,000
Loss and LAE reserve		72,200,000
Tax and loss bonds	71,200,000	56,700,000
NOL carry forward	9,400,000	15,000,000
AMT credit	32,000,000	11,400,000
Tax basis step-up	6,000,000	6,700,000
Foreign tax credit	30,200,000	22,300,000
DAC	4,700,000
FG VIEs	220,900,000	199,200,000
Other	112,100,000	63,000,000
Total deferred income tax assets	1,177,600,000	1,489,700,000
Deferred tax liabilities:
DAC		2,300,000
Contingency reserves	75,600,000	61,100,000
Loss and LAE reserve	1,000,000
Tax basis of public debt	104,800,000	107,100,000
Unrealized appreciation on investments	135,900,000	18,300,000
Unrealized gains on CCS	19,100,000	6,600,000
Other	70,300,000	35,200,000
Total deferred income tax liabilities	406,700,000	230,600,000
Net deferred income tax asset	770,943,000	1,259,125,000	1,274,200,000
Foreign tax credit carry forward	30,200,000	22,300,000
AMT credit	32,000,000	11,400,000
Foreign tax credits from acquisition of AGMH	22,300,000
Uncertain tax positions
Balance at the beginning of the period	18,300,000	23,900,000	5,100,000
Impact from AGMH Acquisition			9,300,000
True-up from tax return filings		(7,700,000)
Increase in unrecognized tax benefits as a result of position taken during the current period	2,100,000	2,100,000	9,500,000
Balance at the end of the period	20,400,000	18,300,000	23,900,000
Interest accrued during the period	600,000
Interest accrued at the end of the period	2,800,000
Unrecognized tax benefits that would affect the effective tax rate, if recognized	20,400,000
Liability for tax basis step-up adjustment	6,900,000	8,000,000
Reduction in liability for tax basis step-up adjustments	1,100,000
Period after tax allocation agreement after which company and AFS will negotiate settlement of unrealized tax benefit (in years)	15 years
Period for which cumulative operating income was considered for assessment of realization of deferred tax assets (in years)	3 years
AGRO
Net operating loss carryforwards
Stand alone NOL	27,000,000	42,900,000
Stand alone NOL available through 2019	6,300,000
Stand alone NOL available through 2023	20,700,000
Valuation allowance			7,000,000
Valuation allowance for NOLs released		$ 7,000,000