Investments - Restricted Investments (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Security Owned Not Readily Marketable [Line Items]
Assets Held by Insurance Regulators	$ 2,339	$ 2,189
Restricted Investments	3,488	3,138
Fair Value Measured at Net Asset Value Per Share [Member]
Security Owned Not Readily Marketable [Line Items]
Deposit Assets	75	62
Syndicate Policyholders [Member] | Fixed maturities
Security Owned Not Readily Marketable [Line Items]
Debt Securities, Available-for-sale, Restricted	890	718
Syndicate Policyholders [Member] | Short-term Investments [Member]
Security Owned Not Readily Marketable [Line Items]
Restricted Investments, Current	30	8
Lloyd's of London [Member] | Fixed maturities
Security Owned Not Readily Marketable [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 154	$ 161