Investment Information - Net investment Income (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net investment income:
Gross investment income		$ 1,586	$ 1,100	$ 567
Investment expenses		(91)	(77)	(71)
Net investment income		1,495	1,023	496
Fixed maturities
Net investment income:
Gross investment income		1,266	917	469
Short-term investments
Net investment income:
Gross investment income		144	68	29
Equity securities
Net investment income:
Gross investment income		40	22	22
Other
Net investment income:
Gross investment income	[1]	$ 136	$ 93	$ 47

[1] Amounts include dividends and other distributions on investment funds, term loan investments, funds held balances, cash balances and other items.