Impact of Catastrophe Costs (Details 3) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Impact of Catastrophe Costs
Net catastrophe costs	$ 66.4	$ 26.9	$ 611.8	$ 157.3
Catastrophe | Domestic
Impact of Catastrophe Costs
Net catastrophe costs	23.6	(3.8)	58.6	(0.8)
Catastrophe | International-Europe
Impact of Catastrophe Costs
Net catastrophe costs	0.2	20.1	110.4	74.1
Catastrophe | International-Other.
Impact of Catastrophe Costs
Net catastrophe costs	$ 42.6	$ 10.6	$ 442.8	$ 84.0