Loss And Loss Adjustment Expense Reserves (Activity In The Reserves For Losses And Loss Adjustment Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of period	$ 2,584,910	$ 2,226,430
Reinsurance recoverables on unpaid losses	25,322	41,377
Net reserves, beginning of period	2,559,588	2,185,053
Incurred losses and loss adjustment expenses related to:
Current year	945,013	769,022
Prior years	(15,484)	52,911
Total incurred losses and loss adjustment expenses	929,529	821,933
Loss and loss adjustment expense payments related to:
Current year	310,102	261,115
Prior years	531,755	471,258
Total payments	841,857	732,373
Net reserves, end of period	2,647,260	2,274,613
Reinsurance recoverables on unpaid losses, end of period	30,301	33,213
Gross reserves, end of period	$ 2,677,561	$ 2,307,826