Investments - Schedule of Gross Realized Gains (Losses) on Sales of Fixed Income Securities (Details) - Fixed income securities - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Debt Securities, Available-for-Sale [Line Items]
Gross realized gains	$ 41	$ 46
Gross realized losses	$ (146)	$ (173)

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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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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