Investments - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Net Investment Income [Line Items]
Investment income, operating	$ 740	$ 663	$ 1,372	$ 1,356
Investment expenses	(26)	(24)	(50)	(48)
Net investment income	714	639	1,322	1,308
Aggregate income (loss) recognized due to the change in fair value of equity and trading portfolio securities held	30	(21)	(10)	19
Fixed maturity securities
Net Investment Income [Line Items]
Investment income, operating	536	511	1,057	1,013
Limited partnership investments
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	81	74	137	128
Short-term investments
Net Investment Income [Line Items]
Investment income, operating	16	20	35	49
Equity securities
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	27	13	33	35
Income from trading portfolio
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	52	11	56	69
Other
Net Investment Income [Line Items]
Investment income, operating	$ 28	$ 34	$ 54	$ 62

Amount, before investment expenses, of gains (losses) on investments.

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Trading Securities, Change in Unrealized Holding Gain (Loss), Net Investment Income Recognized

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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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Amount of expenses related to the generation of investment income.

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Amount, after 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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