Reserve For Losses, LAE And Future Policy Benefit Reserve (Summary Of Activity In The Reserve For Losses And LAE) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Reserve For Losses, LAE And Future Policy Benefit Reserve [Abstract]
Gross reserves beginning of period	$ 13,611,313	$ 13,119,090
Less reinsurance recoverables	(1,640,712)	(1,619,641)
Net reserves beginning of period	11,970,601	11,499,449
Incurred related to: Current year	2,835,129	2,135,335
Incurred related to: Prior years	2,727	7,845
Total incurred losses and LAE	2,837,856	2,143,180
Paid related to: Current year	570,460	374,123
Paid related to: Prior years	1,579,931	1,598,544
Total paid losses and LAE	2,150,391	1,972,667
Foreign exchange/translation adjustment	(74,372)	(57,392)
Net reserves end of period	12,583,694	11,612,570
Plus reinsurance recoverables	1,692,947	1,636,918
Gross reserves end of period	$ 14,276,641	$ 13,249,488