Loss and Loss Adjustment Expenses - Reconciliation of Beginning and Ending Reserve Balances, Net of Related Amounts Recoverable from Reinsurers (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Unpaid Claims and Claims Adjustment Expense, Activity in Liability [Abstract]
Balance, beginning of period	$ 745,278	$ 760,561	$ 772,887
Less amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	119,266	105,707	95,343
Net balance, beginning of period	626,012	654,854	677,544
Add incurred related to:
Current accident year	192,907	222,715	220,710
Prior accident years	(40,591)	(61,917)	(63,484)
Total incurred	152,316	160,798	157,226
Less paid related to:
Current accident year	50,954	52,292	50,113
Prior accident years	143,892	137,348	129,803
Total paid	194,846	189,640	179,916
Net balance, end of period	583,482	626,012	654,854
Add amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	112,555	119,266	105,707
Balance, end of period	$ 696,037	$ 745,278	$ 760,561