Investments - Restricted Investments (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Security Owned Not Readily Marketable [Line Items]
Assets Held by Insurance Regulators	$ 2,362	$ 2,339
Restricted Investments	3,504	3,488
Fair Value Measured at Net Asset Value Per Share [Member]
Security Owned Not Readily Marketable [Line Items]
Deposit Assets	61	75
Syndicate Policyholders [Member] \| Fixed maturities
Security Owned Not Readily Marketable [Line Items]
Debt Securities, Available-for-sale, Restricted	1,056	890
Syndicate Policyholders [Member] \| Short-term Investments [Member]
Security Owned Not Readily Marketable [Line Items]
Restricted Investments, Current	25	30
Lloyd's of London [Member] \| Fixed maturities
Security Owned Not Readily Marketable [Line Items]
Debt Securities, Available-for-sale, Restricted	$ 0	$ 154

Carrying amount of cash and investment securities on deposit with state regulatory authorities in connection with capital requirements.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 825
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477351/944-825-50-1A

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- Definition

Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481420/860-30-50-1A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477220/954-210-45-4

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478600/954-210-50-2

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- Definition

The carrying amount of the asset transferred to a third party to serve as a deposit, which typically serves as security against failure by the transferor to perform under terms of an agreement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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- Definition

Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

+ References

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- Definition

This element represents the current portion of investments which are not defined as or included in marketable (debt, equity, or other) securities that are pledged or subject to withdrawal restrictions.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 45
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477220/954-210-45-4

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 210
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478600/954-210-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 940
-SubTopic 820
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478119/940-820-50-1

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