Deferred Policy Acquisition Costs - Schedule of Activity in the Deferred Policy Acquisition Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 19,048	$ 19,734	$ 20,251
Policy acquisition costs deferred	40,345	43,872	45,252
Amortization expense during the year	(41,583)	(44,558)	(45,769)
Balance, end of year	$ 17,810	$ 19,048	$ 19,734