Investment Information - Net investment Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net investment income:
Gross investment income		$ 1,100	$ 567	$ 478
Investment expenses		(77)	(71)	(89)
Net investment income		1,023	496	389
Fixed maturities available for sale, at fair value (amortized cost: $24,131 and $21,282; net of allowance for credit losses: $28 and $41)
Net investment income:
Gross investment income		917	469	331
Short-term investments
Net investment income:
Gross investment income		68	29	7
Equity securities
Net investment income:
Gross investment income		22	22	42
Term loan investments
Net investment income:
Gross investment income		0	0	30
Other
Net investment income:
Gross investment income	[1]	$ 93	$ 47	$ 68

[1] Includes interest income on operating cash, distributions from investment funds and other items.