Reinsurance - Schedule of the Effect of Reinsurance on Premiums Written and Earned (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Premiums Written and Earned [Abstract]
Gross Written									$ 373,055	$ 386,529	$ 393,819
Ceded Written									(10,307)	(11,228)	(13,793)
Net premiums Written									362,748	375,301	380,026
Gross Earned									379,011	387,122	389,540
Ceded Earned									(10,307)	(11,228)	(13,793)
Net premiums Earned	$ 92,097	$ 89,918	$ 90,728	$ 95,961	$ 95,034	$ 90,504	$ 95,569	$ 94,787	$ 368,704	$ 375,894	$ 375,747