Reserve For Losses, LAE And Future Policy Benefit Reserve (Summary Of Activity In The Reserve For Losses And LAE) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reserve For Losses LAE And Future Policy Benefit Reserve [Abstract]
Gross reserves beginning of period	$ 16,398,997	$ 13,611,313
Less reinsurance recoverables	(1,843,691)	(1,640,712)
Net reserves beginning of period	14,555,306	11,970,601
Incurred related to: Current year	1,713,253	1,433,440
Incurred related to: Prior years	(1,834)	(2,600)
Total incurred losses and LAE	1,711,419	1,430,840
Paid related to: Current year	215,302	168,528
Paid related to: Prior years	837,051	907,790
Total paid losses and LAE	1,052,353	1,076,318
Foreign exchange/translation adjustment	(5,841)	(156,565)
Net reserves end of period	15,208,531	12,168,558
Plus reinsurance recoverables	1,882,113	1,651,946
Gross reserves end of period	$ 17,090,644	$ 13,820,504