Loss Reserves - Change in Allowance for Credit Losses on Amounts Recoverable from Reinsurers (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Insurance [Abstract]
Balance, beginning of period	$ 328	$ 388	$ 372	$ 440
Provision for credit loss expense (benefit)	10	(19)	(34)	(71)
Balance, end of period	$ 338	$ 369	$ 338	$ 369