Loss And Loss Adjustment Expense Reserves (Activity In The Reserves For Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves at January 1	$ 2,226,430	$ 1,991,304	$ 1,921,255
Reissuance recoverables on unpaid losses, beginning of period	41,379	54,461	76,100
Net reserves at January 1	2,185,051	1,936,843	1,845,304
Incurred losses and loss adjustment expenses related to:
Current year	3,314,938	2,786,246	2,372,364
Prior years	47,281	(26,091)	22,979
Total incurred losses and loss adjustment expenses	3,362,219	2,760,155	2,395,343
Loss and loss adjustment expense payments related to:
Current year	1,862,006	1,601,998	1,366,661
Prior years	1,125,677	909,949	937,143
Total payments	2,987,683	2,511,947	2,303,804
Net reserves at December 31	2,559,587	2,185,051	1,936,843
Reissuance recoverables on unpaid losses, end of period	25,323	41,379	54,461
Gross reserves at December 31	2,584,910	2,226,430	1,991,304
Cumulative Effect, Period of Adoption, Adjustment
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Reissuance recoverables on unpaid losses, beginning of period	0	0	(149)
Loss and loss adjustment expense payments related to:
Reissuance recoverables on unpaid losses, end of period		0	0
Cumulative Effect, Period of Adoption, Adjusted Balance
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Reissuance recoverables on unpaid losses, beginning of period	$ 41,379	54,461	75,951
Net reserves at January 1		1,936,843
Loss and loss adjustment expense payments related to:
Net reserves at December 31			1,936,843
Reissuance recoverables on unpaid losses, end of period		$ 41,379	$ 54,461