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, 2024	Mar. 31, 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	2,137	2,603
Prior accident years	(8,606)	(10,110)
Total incurred	39,991	39,009
Less paid related to:
Current accident year	48,597	49,119
Prior accident years	41,522	44,249
Total paid	43,659	46,852
Net balance, end of period	550,580	575,639
Add amounts recoverable from reinsurers on unpaid loss and loss adjustment expenses	117,479	111,013
Balance, end of period	$ 668,059	$ 686,652