Losses and Loss Adjustment Expenses - Losses and LAE (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Net balance, beginning of period*	[1]	$ 254,351	$ 246,546
Incurred, net of reinsurance, related to:
Current period		79,922	56,698
Prior periods		0	3,867
Total incurred, net of reinsurance		79,922	60,565
Paid, net of reinsurance, related to:
Current period		(17,789)	(11,110)
Prior periods		(43,059)	(49,950)
Total paid, net of reinsurance		(60,848)	(61,060)
Net balance, end of period		273,425	246,051
Add: reinsurance recoverable before allowance for credit losses		305,287	560,257
Gross balance, end of period		$ 578,712	$ 806,308	$ 585,073

[1] Net balance represents beginning-of-period liability for unpaid losses and LAE less beginning-of-period reinsurance recoverable for unpaid losses and LAE.