Income Taxes (Schedule Of Pre-Tax Income (Loss) And Effective Income Tax Rates) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Tax Examination [Line Items]
Pre-tax income (loss)	$ 17.7	$ (4.0)	$ 70.8	$ (70.0)
Bermuda [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	8.0	(24.4)	18.2	(110.3)
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
United States [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	12.1	17.1	45.8	67.4
Effective Tax Rate	21.00%	36.40%	22.80%	27.90%
United Kingdom [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	0.1	4.4	13.8	(25.2)
Effective Tax Rate	1217.40%	11.60%	24.00%	22.10%
Belgium [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	0.1	0.1	0.2	0.3
Effective Tax Rate	20.00%	25.50%	33.60%	15.40%
Brazil [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	(1.9)	(1.2)	(5.4)	(2.2)
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
Dubai [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	0	0	0.1	0
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
Ireland [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	0	0	(0.1)	0
Effective Tax Rate	0.00%	0.00%	0.00%	0.00%
Malta [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	(0.7)		(1.8)
Effective Tax Rate	0.00%		0.00%
Switzerland [Member]
Income Tax Examination [Line Items]
Pre-tax income (loss)	$ 0	$ 0		$ 0
Effective Tax Rate	25.00%	0.00%	24.00%	23.10%