Reserve For Losses, LAE And Future Policy Benefit Reserve (Summary Of Activity In The Reserve For Losses And LAE) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 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	4,572,640	3,559,505
Incurred related to: Prior years	1,426	(44,401)
Total incurred losses and LAE	4,574,066	3,515,104
Paid related to: Current year	1,015,538	550,724
Paid related to: Prior years	2,042,712	2,406,753
Total paid losses and LAE	3,058,250	2,957,477
Foreign exchange/translation adjustment	(28,024)	(52,125)
Net reserves end of period	13,458,393	12,004,952
Plus reinsurance recoverables	1,774,732	1,632,687
Gross reserves end of period	$ 15,233,125	$ 13,637,639