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Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Net Investment Income [Line Items]
Investment income	$ 211	$ 206	$ 581	$ 603
Equity in earnings of partnerships and similar investments	27	6	34	45
Investment expenses	(6)	(6)	(19)	(17)
Net investment income	205	200	562	586
Fixed maturities | Net investment income
Net Investment Income [Line Items]
Investment income	148	136	429	406
Fixed maturities | Net investment income
Net Investment Income [Line Items]
Change in fair value of fixed maturity securities	4	7	6	7
Equity securities | Net investment income
Net Investment Income [Line Items]
Dividends	6	6	27	20
Change in fair value of equity securities	(6)	20	(2)	45
Cash and cash equivalents
Net Investment Income [Line Items]
Investment income	14	16	37	40
Other
Net Investment Income [Line Items]
Investment income	$ 18	$ 15	$ 50	$ 40

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