Liability for Unpaid Claims and Claim Adjustment Expenses - Liability for Unpaid Claims and Claim Adjustment Expenses (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 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	434,793
Unpaid claims balance, ending	1,492,965
Property and Casualty Accident and Health
Liability For Unpaid Claims And Claims Adjustment Expense Net
Unpaid claims balance, beginning	1,305,396	$ 1,218,652
Less reinsurance recoverables	254,466	241,301
Net beginning balance	1,050,930	977,351
Incurred related to
Current	917,048	897,901
Prior years	(47,048)	(11,101)
Total incurred claims	870,000	886,800
Paid claims related to
Current	482,729	481,199
Prior years	370,807	338,946
Total paid claims	853,536	820,145
Net balance	1,067,394	1,044,005
Plus reinsurance recoverables	247,174	266,780
Unpaid claims balance, ending	$ 1,314,568	$ 1,310,785