Investments and Cash - Narrative (Details) £ in Millions, $ in Millions		12 Months Ended
	Jul. 01, 2023 USD ($)	Dec. 31, 2024 USD ($) fund security	Dec. 31, 2022 USD ($)	Feb. 27, 2025 USD ($)	Feb. 27, 2025 GBP (£)	Dec. 31, 2023 USD ($) security
Schedule of Cost-method Investments [Line Items]
Fixed-maturity investments, non-investment grade, not rated, percent		12.60%				9.20%
Fixed-maturity securities, available-for-sale		$ 6,369				$ 6,307
Accounted for as consolidated investment vehicles | fund		1
Accrued investment income		$ 64				$ 71
Number of securities with unrealized losses greater than 10% of book value for 12 months or more | security		438				409
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more		$ 223				$ 200
Assets held-in-trust		79				234
Non-income producing investments		42				0
Fixed-maturity securities, trading, at fair value		147				318
Purchased with credit deterioration, amount at purchase price			$ 22
Securities purchased with credit deterioration, amount at par value			31
Allowance for credit loss at acquisition date			2
Discount attributable to other factors			$ 7
Contingent Value Instruments
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, trading, at fair value		123
Loss mitigation securities
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale		479				459
Collateralized Loan Obligation Equity Tranches
Schedule of Cost-method Investments [Line Items]
Fixed-maturity securities, available-for-sale		277				13
Sound Point
Schedule of Cost-method Investments [Line Items]
Equity method investments		$ 418				429
Useful life		5 years 6 months
Disposal Group, Held-for-Sale, Not Discontinued Operations | Sound Point Agreement
Schedule of Cost-method Investments [Line Items]
Investment management commitment	$ 1,000	$ 1,000
Assured Guaranty Subsidiaries
Schedule of Cost-method Investments [Line Items]
Assets held-in-trust		1,135				1,154
Debt Securities Through A Facility | Subsequent Event
Schedule of Cost-method Investments [Line Items]
Purchase commitment, debt securities				$ 139	£ 110
Alternative Investment | Consolidated investment vehicles
Schedule of Cost-method Investments [Line Items]
Equity method investments		33				$ 305
Alternative Investment | Future Equity Investments
Schedule of Cost-method Investments [Line Items]
Fair value of investment		884
Authorized amount to invest		1,500
Unfunded commitment		610
Sound Point
Schedule of Cost-method Investments [Line Items]
Indefinite-lived intangible assets		245
Finite-lived intangible assets		31
Other
Schedule of Cost-method Investments [Line Items]
Fair value of investment		$ 508