Investments (Details) - Fixed Maturities Narrative - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Investment disclosure details
Fixed maturities, at fair value	$ 83,666	$ 77,807
Securities on loan as part of a tri-party lending agreement	586	421
Proceeds from sales of fixed maturities classified as available for sale	1,634	4,981	$ 5,657
Gross realized gains on sales of fixed maturities	2	26	27
Gross realized losses on sales of fixed maturities	62	119	99
Realized losses resulting from the early redemption of fixed maturities by the issuer prior to the bonds' maturity date	66	0	$ 0
Insurance subsidiaries' securities on deposit at financial institutions in certain states pursuant to the respective states' insurance regulatory requirements	3,960	4,040
Fair value of funds deposited with third parties to be used as collateral to secure various liabilities on behalf of insureds, cedants and other creditors	46	54
Subsidiary [Member]
Investment disclosure details
Fair value of owned securities pledged into a Lloyd's trust account to support capital requirements for the Company's operations at Lloyd's	13	31
TRV [Member]
Investment disclosure details
Fixed maturities, at fair value	186	182
Fair value of owned securities pledged into a Lloyd's trust account to support capital requirements for the Company's operations at Lloyd's	86	85
Obligations of U.S. states, municipalities and political subdivisions, pre-refunded [Member]
Investment disclosure details
Fixed maturities, at fair value	572	966
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Investment disclosure details
Fixed maturities, at fair value	12,605	7,818
Residential mortgage-backed pass-through securities classified as available-for-sale, GNMA, FNMA, FHLMC and Canadian Government [Member]
Investment disclosure details
Fixed maturities, at fair value	9,930	6,230
Residential collateralized mortgage obligations [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 2,680	$ 1,590
Percent guaranteed by or fully collateralized by securities issued by GNMA, FNMA or FHLMC	43.00%	33.00%
Non-guaranteed residential collateralized mortgage obligations [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 1,530	$ 1,070
Commercial mortgage-backed securities [Member]
Investment disclosure details
Fixed maturities, at fair value	1,150	1,040
Commercial mortgage-backed securities, containing guarantees by the U.S. government or a government-sponsored enterprise [Member]
Investment disclosure details
Fixed maturities, at fair value	327	116
Commercial mortgage-backed securities, non-guaranteed securities [Member]
Investment disclosure details
Fixed maturities, at fair value	$ 825	$ 922

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