Investments - Additional Information (Detail) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022 USD ($) security	Mar. 31, 2021 security	Dec. 31, 2021 USD ($) security
Gain (Loss) on Securities
Equity Securities at Fair Value	$ 10,675		$ 11,315
Largest Single Common Stock Holding	$ 848		$ 862
Largest equity holdings to total equity portfolio	8.30%		7.90%
Largest equity holdings to total portfolio	3.70%		3.50%
Maximum
Gain (Loss) on Securities
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 1		$ 1
Writedown of Impaired Securities Intended to be Sold	1
Changes in Allowance for Credit Losses During Period	$ 1		$ 1
Fixed maturities
Gain (Loss) on Securities
Number Of Impaired Securities Intended to be Sold | security	1	0
Number Of Securities Continuous Unrealized Loss Position | security	1,377		278
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss 3	$ 245		$ 16
Number Of Securities Continuous Unrealized Loss Position and Below 70 Percent of Amortized Cost	0		0
Fixed maturity investments, Percentage of amortized costs	70.00%		70.00%