Deferred Policy Acquisition Costs - Schedule of Activity in the Deferred Policy Acquisition Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Balance, beginning of year	$ 20,251	$ 19,300	$ 20,412
Policy acquisition costs deferred	45,252	43,960	43,209
Amortization expense during the year	(45,769)	(43,009)	(44,321)
Balance, end of year	$ 19,734	$ 20,251	$ 19,300