Income Taxes (Valuation Allowance) (Details) (USD $)	3 Months Ended								12 Months Ended								2 Months Ended	12 Months Ended			3 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Net operating losses in Luxembourg subsidiaries	Dec. 31, 2012 Net operating losses in Luxembourg subsidiaries	Dec. 31, 2013 U.S. losses and other federal deferred tax benefits	Dec. 31, 2012 U.S. losses and other federal deferred tax benefits	Dec. 31, 2013 Net Operating Losses in Netherlands Subsidiaries [Member] [Member]	Dec. 31, 2013 Luxembourg	Dec. 31, 2013 Luxembourg	Dec. 31, 2013 Luxembourg Tax benefit	Dec. 31, 2013 Luxembourg Tax Expense [Member]	Dec. 31, 2012 Sirius Re Holdings Inc.	Dec. 31, 2013 Sirius Re Holdings Inc.	Dec. 31, 2012 Guilford Holdings, Inc. UNITED STATES	Dec. 31, 2013 BAM	Dec. 31, 2012 BAM	Dec. 31, 2012 Houston General Insurance [Member]
Valuation Allowance [Line Items]
Valuation allowance	$ 289,800,000				$ 254,000,000				$ 289,800,000	$ 254,000,000		$ 195,800,000	$ 192,000,000	$ 93,700,000	$ 62,000,000	$ 300,000
Change in valuation allowance									(33,600,000)	(14,100,000)	128,200,000						(41,300,000)	(1,400,000)	(16,700,000)	(18,100,000)	(3,900,000)		(16,600,000)		(21,300,000)	(6.0)
Income Tax Expense (Benefit)	27,400,000	8,200,000	(600,000)	41,600,000	(101,000,000)	47,800,000	6,400,000	31,100,000	76,600,000	(15,700,000)	(110,000,000)													5,400,000
Foreign tax credit carryforwards, subject to expiration																						$ 5,200,000