Investments (Net investment income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Net Investment Income [Line Items]
Gross investment income	$ 630	$ 544
Investment expense	(21)	(19)
Net investment income	609	525
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	502	470
Equity securities
Net Investment Income [Line Items]
Gross investment income	22	12
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	54
Gross investment loss		25
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	15	14
Short-term investments
Net Investment Income [Line Items]
Gross investment income	28	15
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	1	3
Other
Net Investment Income [Line Items]
Gross investment income	8	5
Common Stock
Net Investment Income [Line Items]
Equity securities, FV-NI, gain (loss)	13	(1)
Non-redeemable preferred stock
Net Investment Income [Line Items]
Equity securities, FV-NI, gain (loss)	$ 11	$ (2)

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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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