Reinsurance Recoverables After Allowance for Credit Losses (Detail) - USD ($) $ in Thousands		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Insurance [Abstract]
Reinsurance recoverables on paid losses		$ 85,300		$ 98,100
Ceded outstanding loss and LAE	[2]	1,703,700	[1]	1,583,900	$ 1,857,400	$ 1,650,100
Reinsurance recoverables, before allowance for credit losses		1,789,000		1,682,000
Allowance for credit losses		(7,900)		0
Total		$ 1,781,096		$ 1,681,962

[1] Includes unallocated LAE, which aggregate to 1.0 percent of gross loss and LAE reserves as of December 31, 2020. Net loss and LAE reserves by component are shown in the preceding tables, and consolidated gross loss and LAE reserves is presented in the consolidated balance sheets.

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