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, 2024	Jun. 30, 2023
Liability for Unpaid Claims and Claims Adjustment Expense, Activity in Liability [Abstract]
Balance, beginning of period	$ 673,994	$ 696,037
Less amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	119,746	112,555
Net balance, beginning of period	554,248	583,482
Add incurred related to:
Current accident year	97,326	95,693
Prior accident years	(16,711)	(21,039)
Total incurred	80,615	74,654
Less paid related to:
Current accident year	12,670	12,938
Prior accident years	74,940	75,252
Total paid	87,610	88,190
Net balance, end of period	547,253	569,946
Add amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	116,732	114,667
Balance, end of period	$ 663,985	$ 684,613