Segments (Textuals) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Decrease In International Segments Pretax Earnings Due To Catastrophe Losses	$ 7,600,000	$ 29,400,000	$ 15,900,000	$ 101,700,000
Decrease In Professional Liability Segments Pretax Earnings Due To Catastrophe Losses		$ 58,500,000		$ 75,400,000