Reserve for Known and Incurred but Not Reported Claims (Activity in Reserve for Known and Incurred but Not Reported Claims) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]
Balance at beginning of period	$ 1,284	$ 1,178
Provision related to current year	115	135
Provision related to prior years	7	5
Total Provision	122	140
Payments, net of recoveries, related to: Current year	33	38
Payments, net of recoveries, related to: Prior years	68	80
Total Payments, net of recoveries	101	118
Other	(4)	3
Balance at end of period	$ 1,301	$ 1,203