Reinsurance - Impact of the Reinsurance Treaties on Premiums Written and Earned (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Premiums Written:
Direct	$ 116,464	$ 97,331	$ 364,942	$ 298,384
Assumed	(13)		(92)	(2)
Gross written	116,451	97,331	364,850	298,382
Ceded	(44,231)	(31,568)	(109,304)	(94,298)
Net premiums written	72,220	65,763	255,546	204,084
Premiums Earned:
Direct	106,337	86,002	303,956	251,916
Assumed	357		2,906	(2)
Gross earned	106,694	86,002	306,862	251,914
Ceded	(44,231)	(31,568)	(109,304)	(94,298)
Net premiums earned	$ 62,463	$ 54,434	$ 197,558	$ 157,616