Investment Information - Net investment income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net investment income:
Gross investment income		$ 289	$ 146	$ 768	$ 372
Investment expenses		(20)	(17)	(58)	(57)
Net investment income		269	129	710	315
Fixed maturities
Net investment income:
Gross investment income		243	124	645	311
Equity securities
Net investment income:
Gross investment income		5	4	15	16
Short-term investments
Net investment income:
Gross investment income		19	9	48	16
Other
Net investment income:
Gross investment income	[1]	$ 22	$ 9	$ 60	$ 29

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