Summarized Activity in Liability for Unpaid Losses and Loss Adjustment Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Insurance [Abstract]
Balance at beginning of period	$ 759,904	$ 662,811
Less: Ceded reinsurance receivables	94,443	82,158
Net balance at beginning of period	665,461	580,653
Incurred losses and loss adjustment expenses related to:
Current year	87,758	94,194
Prior years	(3,063)	(3,411)
Total incurred losses and loss adjustment expenses	84,695	90,783
Paid losses and loss adjustment expenses related to:
Current year	13,315	21,719
Prior years	59,703	53,230
Total paid losses and loss adjustment expenses	73,018	74,949
Net balance at end of period	677,138	596,487
Plus: Ceded reinsurance receivables	93,194	79,421
Balance at end of period	$ 770,332	$ 675,908