Reserve for Known and Incurred but Not Reported Claims (Activity in Reserve for Known and Incurred but Not Reported Claims) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at beginning of period			$ 1,178,004	$ 1,063,044
Provision related to current year			428,501	379,987
Provision related to prior years			17,176	34,014
Total Provision	$ 155,300	$ 157,836	445,677	414,001
Payments, net of recoveries, related to: Current year			204,525	179,654
Payments, net of recoveries, related to: Prior years			151,920	163,067
Total Payments, net of recoveries			356,445	342,721
Other			(5,721)	(3,882)
Reclassification to liabilities previously held for sale				(60,583)
Balance at end of period	$ 1,261,515	$ 1,069,859	$ 1,261,515	$ 1,069,859