Loss Reserves - Liability for Unpaid Loss and Loss Adjustment Expenses, Net of Related Amounts Recoverable from Reinsurers (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 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	48,908	48,597
Prior accident years	(8,749)	(8,606)
Total incurred	40,159	39,991
Less paid related to:
Current accident year	2,037	2,137
Prior accident years	47,225	41,522
Total paid	49,262	43,659
Net balance, end of period	529,464	550,580
Add amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	110,501	117,479
Balance, end of period	$ 639,965	$ 668,059