Summary of Activity in Reserve for Losses and LAE (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Insurance [Abstract]
Net reserves for losses and LAE at beginning of year	$ 1,393,126	$ 1,308,136	$ 1,222,633
Provision for losses and LAE for claims occurring in the current year	693,976	637,267	601,041
Increase (decrease) in estimated losses and LAE for claims occurring in prior years	(28,528)	(64,669)	(55,812)
Incurred losses and LAE	665,448	572,598	545,229
Losses and LAE paid for claims occurring during:
Current year	(119,485)	(159,802)	(158,806)
Prior years	(412,544)	(320,863)	(295,527)
Losses and LAE payments	(532,029)	(480,665)	(454,333)
Foreign Currency Adjustment	(16,094)	(6,943)	(5,393)
Net reserves for losses and LAE at end of year	1,510,451	1,393,126	1,308,136
Reinsurance recoverables on unpaid losses and LAE	779,276	809,518	851,498
Gross reserves for losses and LAE at end of year	$ 2,289,727	$ 2,202,644	$ 2,159,634