Investments - Limited Partnership (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Net Investment Income [Line Items]
Investment, Type [Extensible Enumeration]	Partnership Interest [Member]		Partnership Interest [Member]
Fair Value Measured at Net Asset Value Per Share
Net Investment Income [Line Items]
Alternative investments	$ 252		$ 262
Unfunded additional commitments	147
Net gains (losses) from limited partnership investments	$ 0	$ 0

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

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+ Details

- Definition

Indicates type of investment. Includes, but is not limited to, common stock, preferred stock, convertible security, fixed income security, government security, option purchased, warrant, loan participation and assignment, commercial paper, bankers' acceptance, certificates of deposit, short-term security, repurchase agreement, and other investment company.

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