Investments - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) security	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) security	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) security
Gain (Loss) on Securities
Equity Securities at Fair Value	$ 10,031		$ 10,031		$ 9,841
Largest Single Common Stock Holding	$ 764		$ 764		$ 597
Largest equity holdings to total equity portfolio	7.90%		7.90%		6.30%
Largest equity holdings to total portfolio	3.30%		3.30%		2.70%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 3		$ 3		$ 1
Fixed maturities
Gain (Loss) on Securities
Number Of Securities Continuous Unrealized Loss Position | security	4,490		4,490		3,272
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss 3	$ 1,236		$ 1,236		$ 908
Number Of Securities Continuous Unrealized Loss Position and Below 70 Percent of Amortized Cost	202		202		49
Fixed maturity investments, Percentage of amortized costs	70.00%		70.00%
Change in allowance for credit losses, net	$ (1)	$ (1)	$ 2	$ (1)