Premiums Receivable - Summary of Activity in Allowance for Credit Losses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Premiums Receivable, Allowance for Doubtful Accounts [Roll Forward]
Balance, beginning of year	$ 5,112	$ 5,390
Provision for credit loss expense	1,278	723
Write-offs	(1,599)	(1,001)
Balance, end of year	$ 4,791	$ 5,112