Reserve for Known and Incurred but Not Reported Claims (Activity in Reserve for Known and Incurred but Not Reported Claims) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at beginning of year	$ 1,284	$ 1,178	$ 1,063
Provision related to current year	468	570	532
Provision related to prior years	18	19	48
Total Provision	486	589	580
Payments, net of recoveries, related to: Current year	227	292	268
Payments, net of recoveries, related to: Prior years	207	190	203
Total Payments, net of recoveries	434	482	471
Other	(11)	(1)	6
Balance at end of year	$ 1,325	$ 1,284	$ 1,178