Investments - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($) security	Sep. 30, 2022 USD ($) security	Sep. 30, 2021 USD ($) security	Dec. 31, 2021 USD ($) security
Gain (Loss) on Securities
Equity Securities at Fair Value	$ 8,840		$ 8,840		$ 11,315
Largest Single Common Stock Holding	$ 638		$ 638		$ 862
Largest equity holdings to total equity portfolio	7.60%		7.60%		7.90%
Largest equity holdings to total portfolio	3.10%		3.10%		3.50%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 1		$ 1
Maximum
Gain (Loss) on Securities
Debt Securities, Available-for-sale, Allowance for Credit Loss					$ 1
Changes in Allowance for Credit Losses During Period			1		$ 1
Writedown of Impaired Securities Intended to be Sold			$ 1
Fixed maturities
Gain (Loss) on Securities
Number Of Impaired Securities Intended to be Sold | security	0	5	2	5
Number Of Securities Continuous Unrealized Loss Position | security	4,049		4,049		278
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss 3	$ 1,115		$ 1,115		$ 16
Number Of Securities Continuous Unrealized Loss Position and Below 70 Percent of Amortized Cost	118		118		0
Fixed maturity investments, Percentage of amortized costs			70.00%		70.00%
Writedown of Impaired Securities Intended to be Sold	$ 0	$ 1	$ 0	$ 1