Summary of Components of Net Losses and Loss Adjustment Expenses Incurred (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance [Abstract]
Direct									$ 703,361	$ 657,059	$ 574,020
Assumed									97,947	118,352	133,674
Ceded									(228,710)	(230,182)	(188,733)
Net losses and LAE	$ 153,881	$ 146,546	$ 141,973	$ 130,198	$ 134,658	$ 135,284	$ 140,220	$ 135,067	$ 572,598	$ 545,229	$ 518,961