Investments - Additional Information (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2023 USD ($) security	Mar. 31, 2022 security	Dec. 31, 2022 USD ($) security
Gain (Loss) on Securities
Equity Securities at Fair Value	$ 9,967		$ 9,841
Largest Single Common Stock Holding	$ 758		$ 597
Largest equity holdings to total equity portfolio	7.90%		6.30%
Largest equity holdings to total portfolio	3.30%		2.70%
Debt Securities, Available-for-sale, Allowance for Credit Loss	$ 1		$ 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	0	1
Number Of Securities Continuous Unrealized Loss Position | security	2,900		3,272
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss 3	$ 776		$ 908
Number Of Securities Continuous Unrealized Loss Position and Below 70 Percent of Amortized Cost	26		49
Fixed maturity investments, Percentage of amortized costs	70.00%		70.00%