Investments - Investment Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Fixed maturity securities:
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held	$ (7)	$ (10)	$ (62)	$ (42)
Nonredeemable Preferred Stock
Fixed maturity securities:
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held	4	13	8	24
Fixed maturity securities
Fixed maturity securities:
Gross gains	15	11	33	38
Gross losses	(25)	(33)	(100)	(104)
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held	(10)	(22)	(67)	(66)
Equity securities
Fixed maturity securities:
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held	4	13	10	25
Short-term investments and other
Fixed maturity securities:
Investment gains (losses) recognized due to the change in fair value of non-redeemable preferred stock included within equity securities held	$ (1)	$ (1)	$ (5)	$ (1)