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Investments - Internally Managed Investment Portfolio (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items]
Estimated fair value	$ 6,284	$ 6,307
Fixed-maturity securities, trading	163	318
Short-term investments, at fair value	1,487	1,661
Other invested assets	912	829
Total investments	$ 8,846	$ 9,115
Fixed-maturity investments, non-investment grade, percent	9.10%	9.20%
Sound Point Capital Management, LP
Debt and Equity Securities, FV-NI [Line Items]
Equity method investments	$ 417	$ 429
Total investments	288	202
Externally managed
Debt and Equity Securities, FV-NI [Line Items]
Estimated fair value	5,554	5,372
Loss Mitigation Securities
Debt and Equity Securities, FV-NI [Line Items]
Estimated fair value	468	459
Other
Debt and Equity Securities, FV-NI [Line Items]
Estimated fair value	262	476
Contingent Value Instruments
Debt and Equity Securities, FV-NI [Line Items]
Fixed-maturity securities, trading	136	318
Alternative Investment
Debt and Equity Securities, FV-NI [Line Items]
Equity method investments	487	394
Alternative Investment | Consolidated Investment Vehicles
Debt and Equity Securities, FV-NI [Line Items]
Equity method investments	278	305
Other
Debt and Equity Securities, FV-NI [Line Items]
Other invested assets	$ 8	$ 6

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