Investments - Restricted Investments (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Schedule of Investments [Line Items]
Assets Held by Insurance Regulators	$ 2,291	$ 2,189
Restricted Investments	3,327	3,138
Fair Value Measured at Net Asset Value Per Share [Member]
Schedule of Investments [Line Items]
Deposit Assets	70	62
Syndicate Policyholders [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	797	718
Syndicate Policyholders [Member] | Short-term investments
Schedule of Investments [Line Items]
Restricted Investments, Current	6	8
Lloyd's of London [Member] | Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 163	$ 161