Reserve For Losses, LAE And Future Policy Benefit Reserve (Summary Of Activity In The Reserve For Losses And LAE) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reserve For Losses, LAE And Future Policy Benefit Reserve [Abstract]
Gross reserves at January 1	$ 9,340,183	$ 8,937,858	$ 8,840,660
Less reinsurance recoverables	(689,445)	(641,269)	(690,509)
Net reserves at January 1	8,650,738	8,296,589	8,150,151
Current year	3,722,513	2,976,578	2,245,220
Prior years	3,691	(30,866)	128,838
Total incurred losses and LAE	3,726,204	2,945,712	2,374,058
Current year	810,530	568,330	388,172
Prior years	2,008,307	1,988,749	1,997,216
Total paid losses and LAE	2,818,837	2,557,079	2,385,388
Foreign exchange/translation adjustment	(15,888)	(34,484)	157,768
Net reserves at December 31	9,542,217	8,650,738	8,296,589
Plus reinsurance recoverables	580,998	689,445	641,269
Gross reserves at December 31	$ 10,123,215	$ 9,340,183	$ 8,937,858