Loss Reserves - Liability for Unpaid Loss and Loss Adjustment Expenses, Net of Related Amounts Recoverable from Reinsurers (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Liability for Unpaid Claims and Claims Adjustment Expense, Activity in Liability [Abstract]
Balance, beginning of period	$ 651,309	$ 673,994
Less amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	112,742	119,746
Net balance, beginning of period	538,567	554,248
Add incurred related to:
Current accident year	98,170	97,326
Prior accident years	(17,351)	(16,711)
Total incurred	80,819	80,615
Less paid related to:
Current accident year	15,305	12,670
Prior accident years	90,805	74,940
Total paid	106,110	87,610
Net balance, end of period	513,276	547,253
Add amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	110,819	116,732
Balance, end of period	$ 624,095	$ 663,985