Investments - Investment Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Investment Gains (Losses) [Abstract]
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held as of March 31, 2024 and 2023	$ (22)	$ (35)
Nonredeemable Preferred Stock
Investment Gains (Losses) [Abstract]
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held as of March 31, 2024 and 2023	11	(2)
Fixed maturity securities
Investment Gains (Losses) [Abstract]
Gross gains	14	35
Gross losses	(46)	(57)
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held as of March 31, 2024 and 2023	(32)	(22)
Equity securities
Investment Gains (Losses) [Abstract]
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held as of March 31, 2024 and 2023	11	(14)
Short-term investments and other
Investment Gains (Losses) [Abstract]
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held as of March 31, 2024 and 2023	$ (1)	$ 1