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, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Gross reserves, beginning of period	$ 2,584,910	$ 2,226,430	$ 1,991,304
Reinsurance recoverables on unpaid losses, beginning of period	(25,323)	(41,379)	(54,461)
Net reserves, beginning of period	2,559,587	2,185,051	1,936,843
Incurred losses and loss adjustment expenses related to:
Current year	3,553,801	3,314,938	2,786,246
Prior years	(35,948)	47,281	(26,091)
Total incurred losses and loss adjustment expenses	3,517,853	3,362,219	2,760,155
Loss and loss adjustment expense payments related to:
Current year	2,080,690	1,862,006	1,601,998
Prior years	1,243,196	1,125,677	909,949
Total payments	3,323,886	2,987,683	2,511,947
Net reserves, end of period	2,753,554	2,559,587	2,185,051
Reinsurance recoverables on unpaid losses, end of period	32,148	25,323	41,379
Gross reserves, end of period	$ 2,785,702	$ 2,584,910	$ 2,226,430