Loss And Loss Adjustment Expense Reserves - Reconciliation of the Disclosure of Incurred and Paid Claims Development to the Loss and Loss Adjustment Expense Reserves (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	$ 2,059,835
Reinsurance recoverables on unpaid losses	41,379
Insurance lines other than short-duration	706
Unallocated claims adjustment expenses	124,510
Unallocated claims adjustment expenses, aggregate reconciling items	125,216
Total gross loss and loss adjustment expense reserves	2,226,430	$ 1,991,304	$ 1,921,255	$ 1,829,412
Property insurance product line, automobile
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	1,625,317
Reinsurance recoverables on unpaid losses	16,416
Property insurance product line, homeowners'
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	286,129
Reinsurance recoverables on unpaid losses	23,958
Other Short-duration Insurance Product Line
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Net outstanding liabilities	148,389
Reinsurance recoverables on unpaid losses	$ 1,005