Investments - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net Investment Income [Line Items]
Investment income, operating	$ 800	$ 615	$ 2,156	$ 1,819
Investment expenses	(24)	(23)	(72)	(67)
Net investment income	776	592	2,084	1,752
Net investment income (loss) recognized due to the change in fair value of equity and trading portfolio securities held	108	(14)	123	3
Fixed maturity securities
Net Investment Income [Line Items]
Investment income, operating	517	491	1,530	1,443
Limited partnership investments
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	67	29	195	111
Short-term investments
Net Investment Income [Line Items]
Investment income, operating	21	24	70	54
Equity securities
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	21	9	56	42
Income from trading portfolio
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	141	32	210	91
Other
Net Investment Income [Line Items]
Investment income, operating	$ 33	$ 30	$ 95	$ 78

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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