Investments (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]
Gross investment income	$ 660	$ 647	$ 1,971	$ 1,916
Investment expense	(22)	(21)	(67)	(63)
Net investment income	638	626	1,904	1,853
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	541	517	1,599	1,530
Equity securities
Net Investment Income [Line Items]
Gross investment income	12	21	45	56
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	68	67	205	195
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	16	14	48	43
Short-term investments
Net Investment Income [Line Items]
Gross investment income	19	20	52	68
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	(1)	0	3	1
Other
Net Investment Income [Line Items]
Gross investment income	5	8	19	23
Common Stock
Net Investment Income [Line Items]
Net investment income (loss) recognized due to the change in fair value of common stock held as of September 30, 2025 and 2024	$ 3	$ 11	$ 15	$ 20

Gross Investment Income, Operating, Net

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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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Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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