Summary of Reserves for Losses and LAE Activity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Insurance [Abstract]
Net reserves for losses and LAE at beginning of year	$ 1,510,451	$ 1,393,126
Provision for losses and LAE for claims occurring in the current year	162,515	154,790
Increase (decrease) in estimated losses and LAE for claims occurring in prior years	7,085	(1,834)
Incurred losses and LAE	169,600	152,956
Losses and LAE paid for claims occurring during:
Current year	(16,287)	(15,325)
Prior years	(126,722)	(112,084)
Losses and LAE payments	(143,009)	(127,409)
Foreign currency adjustment	(226)	(457)
Net reserves for losses and LAE at end of period	1,536,816	1,418,216
Reinsurance recoverables on unpaid losses and LAE	794,576	793,632	$ 779,276
Reserves for losses and loss adjustment expenses	$ 2,331,392	$ 2,211,848	$ 2,289,727