Investments - Schedule of Gross Realized Gains (Losses) on Sales of Fixed Income Securities (Details) - Fixed income securities - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Debt Securities, Available-for-Sale [Line Items]
Gross realized gains	$ 14	$ 142	$ 199	$ 329
Gross realized losses	$ (414)	$ (35)	$ (715)	$ (600)

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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+ Details