Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Net Investment Income [Line Items]
Investment income	$ 802	$ 758	$ 733
Equity in earnings of partnerships and similar investments	46	99	267
Investment expenses	(22)	(16)	(16)
Net investment income	780	742	717
Net investment income
Net Investment Income [Line Items]
Change in fair value of equity securities	57	36	(2)
Fixed maturities | Net investment income
Net Investment Income [Line Items]
Change in fair value of fixed maturities	17	(3)	0
Fixed maturities | Net investment income
Net Investment Income [Line Items]
Investment income	544	502	376
Equity securities | Net investment income
Net Investment Income [Line Items]
Dividends	29	34	39
Cash and cash equivalents
Net Investment Income [Line Items]
Investment income	56	43	11
Other
Net Investment Income [Line Items]
Investment income	$ 53	$ 47	$ 42