Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign tax credit carryforwards.

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Income Taxes (Valuation Allowance) (Details) (USD $)	3 Months Ended								12 Months Ended			3 Months Ended
Income Taxes (Valuation Allowance) (Details) (USD $)	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2012
Valuation Allowance [Line Items]
Valuation allowance	$ 274,600,000				$ 289,800,000				$ 274,600,000	$ 289,800,000
Valuation allowance									18,100,000	33,600,000	14,100,000
Income Tax Expense (Benefit)	(8,700,000)us-gaap_IncomeTaxExpenseBenefit	7,800,000us-gaap_IncomeTaxExpenseBenefit	23,900,000us-gaap_IncomeTaxExpenseBenefit	30,300,000us-gaap_IncomeTaxExpenseBenefit	27,400,000us-gaap_IncomeTaxExpenseBenefit	8,200,000us-gaap_IncomeTaxExpenseBenefit	(600,000)us-gaap_IncomeTaxExpenseBenefit	41,600,000us-gaap_IncomeTaxExpenseBenefit	53,300,000us-gaap_IncomeTaxExpenseBenefit	76,600,000us-gaap_IncomeTaxExpenseBenefit	(15,700,000)us-gaap_IncomeTaxExpenseBenefit
Net operating losses in Luxembourg subsidiaries
Valuation Allowance [Line Items]
Valuation allowance	164,800,000				195,800,000				164,800,000	195,800,000
U.S. losses and other federal deferred tax benefits
Valuation Allowance [Line Items]
Valuation allowance	107,600,000				93,700,000				107,600,000	93,700,000
Net Operating Losses in Israel Subsidiaries [Member]
Valuation Allowance [Line Items]
Valuation allowance	1,900,000								1,900,000
Net Operating Losses in Netherlands Subsidiaries [Member] [Member]
Valuation Allowance [Line Items]
Valuation allowance	300,000				300,000				300,000	300,000
Luxembourg
Valuation Allowance [Line Items]
Valuation allowance									1,200,000	1,400,000		(41,300,000)
Luxembourg \| Tax Benefit [Member]
Valuation Allowance [Line Items]
Valuation allowance									(14,300,000)	(16,700,000)
Luxembourg \| Tax Expense [Member]
Valuation Allowance [Line Items]
Valuation allowance									15,500,000	18,100,000
Sirius Re Holdings Inc.
Valuation Allowance [Line Items]
Valuation allowance	100,000								100,000
Foreign tax credit carryforwards, subject to expiration	12,100,000								12,100,000
Sirius Re Holdings Inc. \| Tax Benefit [Member]
Valuation Allowance [Line Items]
Valuation allowance									(3,800,000)
Sirius Re Holdings Inc. \| Tax Expense [Member]
Valuation Allowance [Line Items]
Valuation allowance												3,900,000
Guilford Holdings, Inc. \| UNITED STATES
Valuation Allowance [Line Items]
Valuation allowance									7,200,000	16,600,000
BAM
Valuation Allowance [Line Items]
Valuation allowance									8,500,000	21,300,000
Income Tax Expense (Benefit)									4,900,000	5,400,000
Houston General Insurance [Member]
Valuation Allowance [Line Items]
Valuation allowance									(100,000)	6.0
Star & Shield Insurance Exchange [Member]
Valuation Allowance [Line Items]
Valuation allowance									$ (3,200,000)