Investments - Net Investment Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net Investment Income [Line Items]
Investment income, operating	$ 615	$ 425	$ 1,819	$ 1,264
Investment expenses	(23)	(21)	(67)	(62)
Net investment income	592	404	1,752	1,202
Net investment income (loss) recognized due to the change in fair value of equity and trading portfolio securities held as of September 30, 2023 and 2022	(14)	(68)	3	(179)
Fixed maturity securities
Net Investment Income [Line Items]
Investment income, operating	491	454	1,443	1,324
Limited partnership investments
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	29	(32)	111	(5)
Short term investments
Net Investment Income [Line Items]
Investment income, operating	24		54
Equity securities
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	9	2	42	(7)
Income (loss) from trading portfolio
Net Investment Income [Line Items]
Gain (losses) on investments, before investment expenses	32	(18)	91	(95)
Other
Net Investment Income [Line Items]
Investment income, operating	$ 30	$ 19	$ 78	$ 47

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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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