Liability for Unpaid Claims and Claim Adjustment Expenses - Liability for Unpaid Claims and Claim Adjustment Expenses (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Liability For Unpaid Claims And Claims Adjustment Expense Net
Unpaid claims balance, beginning	$ 1,481,294
Less reinsurance recoverables	427,475
Paid claims related to
Plus reinsurance recoverables	437,152
Unpaid claims balance, ending	1,477,780
Property and Casualty Accident and Health
Liability For Unpaid Claims And Claims Adjustment Expense Net
Unpaid claims balance, beginning	1,305,396	$ 1,218,824
Less reinsurance recoverables	254,466	241,302
Net beginning balance	1,050,930	977,522
Incurred related to
Current	591,073	586,516
Prior years	(30,691)	(2,501)
Total incurred claims	560,382	584,015
Paid claims related to
Current	272,650	261,019
Prior years	276,738	268,116
Total paid claims	549,388	529,135
Net balance	1,061,924	1,032,402
Plus reinsurance recoverables	249,245	255,684
Unpaid claims balance, ending	$ 1,311,169	$ 1,288,086