Reinsurance - Impact of the Reinsurance Treaties on Premiums Written and Earned (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Premiums Written:
Direct	$ 94,935	$ 93,282	$ 301,930	$ 308,682
Assumed	(63)	(18)	(1,184)	(377)
Gross written	94,872	93,264	300,746	308,305
Ceded	(44,704)	(29,242)	(101,528)	(105,998)
Net premiums written	50,168	64,022	199,218	202,307
Premiums Earned:
Direct	87,118	92,112	259,698	283,011
Assumed	1,551	430	10,678	3,262
Gross earned	88,669	92,542	270,376	286,273
Ceded	(44,705)	(29,242)	(101,529)	(105,998)
Net premiums earned	$ 43,964	$ 63,300	$ 168,847	$ 180,275