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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Insurance [Abstract]
Balance, beginning of period	$ 388	$ 452	$ 440	$ 452
Provision for credit loss benefit	(19)	(3)	(71)	(3)
Balance, end of period	$ 369	$ 449	$ 369	$ 449