Reinsurance Recoverables, Recorded After Allowance for Credit Losses (Detail) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Insurance [Abstract]
Reinsurance recoverables on paid losses		$ 75,900	$ 98,100
Ceded outstanding loss and LAE	[1]	1,559,500	1,583,900	$ 1,642,800	$ 1,857,400
Reinsurance recoverables, before allowance for credit losses		1,635,400	1,682,000
Allowance for credit losses		(6,800)
Total		$ 1,628,649	$ 1,681,962

[1] Reinsurance recoverables in this table include only ceded loss and LAE reserves.