Investments - Net Investment Income (Details) $ in Millions	12 Months Ended
Dec. 31, 2023 USD ($) Investment	Dec. 31, 2022 USD ($) Investment	Dec. 31, 2021 USD ($)
Net Investment Income [Line Items]
Investment income, operating	$ 2,489	$ 1,886	$ 2,334
Investment expenses	(94)	(84)	(75)
Net investment income	2,395	1,802	2,259
Net investment income recognized due to the change in fair value of equity and trading portfolio securities held as of December 31	$ 38	$ 3	23
Number of investments in single issuer exceeding 10% \| Investment	0	0
Fixed maturity securities
Net Investment Income [Line Items]
Investment income, operating	$ 1,941	$ 1,787	1,707
Limited partnership investments
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	177	(6)	375
Short-term investments
Net Investment Income [Line Items]
Investment income, operating	78	17	2
Equity securities
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	63	23	83
Income from trading portfolio
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	125		106
Other
Net Investment Income [Line Items]
Investment income, operating	$ 105	$ 65	$ 61

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

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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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