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, 2022	Mar. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of period	$ 2,226,430	$ 1,991,304
Reinsurance recoverables on unpaid losses	41,377	54,460
Net reserves, beginning of period	2,185,053	1,936,844
Incurred losses and loss adjustment expenses related to:
Current year	769,022	627,551
Prior years	52,911	(1,207)
Total incurred losses and loss adjustment expenses	821,933	626,344
Loss and loss adjustment expense payments related to:
Current year	261,115	242,103
Prior years	471,258	334,867
Total payments	732,373	576,970
Net reserves, end of period	2,274,613	1,986,218
Reinsurance recoverables on unpaid losses, end of period	33,213	54,882
Gross reserves, end of period	$ 2,307,826	$ 2,041,100