Investments (Net investment income) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Net Investment Income [Line Items]
Gross investment income	$ 639	$ 594	$ 1,269	$ 1,138
Investment expense	(21)	(19)	(42)	(38)
Net investment income	618	575	1,227	1,100
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	511	482	1,013	952
Equity securities
Net Investment Income [Line Items]
Gross investment income	13	21	35	33
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	74	55	128	80
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	14	14	29	28
Short-term investments
Net Investment Income [Line Items]
Gross investment income	20	13	48	28
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	0	0	1	3
Other
Net Investment Income [Line Items]
Gross investment income	7	9	15	14
Common Stock
Net Investment Income [Line Items]
Equity securities, FV-NI, gain (loss)	2	10	11	7
Non-redeemable preferred stock
Net Investment Income [Line Items]
Equity securities, FV-NI, gain (loss)	$ 1	$ 3	$ 12	$ 0

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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