Losses and Loss Adjustment Expenses - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Effects of Reinsurance [Line Items]
Net incurred losses and LAE	$ (96,462)	$ (65,900)	$ (179,680)	$ (136,036)
Net incurred losses and LAE, current period	126,634	121,335	241,936	234,349
Net incurred losses and LAE, prior periods	30,172	55,435	62,256	98,313
Non-Life Run-Off
Effects of Reinsurance [Line Items]
Net incurred losses and LAE	24,690	28,870	48,244	41,970
Net incurred losses and LAE, current period	518	22,547	6,587	43,273
Current year premiums earned	500	17,200	5,000	35,800
Net incurred losses and LAE, prior periods	25,208	51,417	54,831	85,243
Increase (reduction) in estimates of net ultimate losses, prior period	(35,074)	(38,394)	(54,233)	(38,138)
Increase (reduction) in provisions for bad debt, prior period	(5,184)	(625)	(6,630)	(20,439)
Increase (reduction) in provisions for unallocated loss adjustment expense liabilities, prior period	(6,355)	(7,711)	(14,590)	(21,686)
Amortization of fair value adjustments, prior period	$ 21,405	$ (4,687)	$ 20,622	$ (4,980)